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Special Issue "Environmental Stress and Plants"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Plant Sciences".

Deadline for manuscript submissions: 31 May 2021.

Special Issue Editors

Prof. Dr. Giampiero Cai
E-Mail Website
Guest Editor
Department of Life Sciences, University of Siena, Siena, Italy
Interests: cytoskeleton; cell wall; organelle movement; cell morphogenesis; plant reproduction; abiotic stress
Special Issues and Collections in MDPI journals
Dr. Luigi Parrotta
E-Mail Website
Guest Editor
Department of Biological, Geological, and Environmental Sciences, University of Bologna, Bologna, Italy
Interests: environmental stress; pollen tube growth; cell wall; allergens; plant cell cytoskeleton
Dr. Lavinia Mareri
E-Mail Website
Guest Editor
Department of Life Sciences, University of Siena, Siena, Italy
Interests: abiotic stress; plant reproduction; plant biodiversity; cell wall; genetic and molecular stress responses

Special Issue Information

Dear Colleagues,

Due to their sessile nature, land plants are often exposed to a multitude of unfavorable, or even adverse, environmental conditions. Among them, abiotic stresses (such as salinity, drought, heat, cold, heavy metals, ozone, ultraviolet radiation, and nutrient deficiencies) are major constraints that affect plant development, growth, and reproduction and pose serious threats to plants’ life. The frequency, intensity, and duration of these adverse environmental conditions are predicted to be boosted by the alarming scenario of global warming with a negative impact on crop yield and therefore on food production. Plants respond to abiotic stresses by changing many aspects, from gene expression to plant physiology and architecture through primary and secondary metabolism. These complex changes allow plants to tolerate and/or adapt to adverse conditions. The complexity of the plant response is further increased by evidence that it can be affected by several factors, including the duration and intensity of stress, the plant genotype, the simultaneous occurrence of different stresses, and the developmental stages at which the plant perceives stress. Considering how complex the response of plants is and how it can be modified by a number of other factors, it is important to gain a deeper understanding of how plants feel stressful conditions and how they respond and adapt (both in natural and anthropized environments). New knowledge acquired through the research of abiotic stress tolerance mechanisms will help in the application of stress-responsive determinants and in engineering plants with enhanced tolerance to stress. This is of importance in the scenario of future environmental changes and the progressive increase in the human population.

This Special Issue aims to collect scientific contributions (in the form of reviews or original articles) that can gain more insight into the effects of single and combined abiotic stresses on plant functioning at cell, tissue, organ, and whole plant level. Apart from the general subject of the Special Issue, there are no particular constraints, and authors are invited to submit articles on topics that can describe the response/adaptation of plants to individual and combined abiotic stresses, including the relevance of stress priming and stress memory in plants. Articles or reviews that, in addition to describing the effects of abiotic stress on plants, highlight possible solutions in terms of new genotypes or new molecular responses (both naturally present and induced by biotechnological approaches) are of particular interest. Authors are also encouraged to submit articles where use is made of multiplex approaches ranging from molecular biology to biochemistry and physiology to better elucidate plant responses to adverse stimuli.

Prof. Dr. Giampiero Cai
Dr. Luigi Parrotta
Dr. Lavinia Mareri
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • combined abiotic stress
  • priming and stress memory
  • salinity
  • heat stress
  • cold stress
  • drought
  • UV radiation
  • nutrient deficiency/toxicity

Published Papers (31 papers)

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Open AccessArticle
Functional Characterization of a Sugar Beet BvbHLH93 Transcription Factor in Salt Stress Tolerance
Int. J. Mol. Sci. 2021, 22(7), 3669; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22073669 - 01 Apr 2021
Viewed by 227
Abstract
The basic/helix–loop–helix (bHLH) transcription factor (TF) plays an important role for plant growth, development, and stress responses. Previously, proteomics of NaCl treated sugar beet leaves revealed that a bHLH TF, BvbHLH93, was significantly increased under salt stress. The BvbHLH93 protein localized in [...] Read more.
The basic/helix–loop–helix (bHLH) transcription factor (TF) plays an important role for plant growth, development, and stress responses. Previously, proteomics of NaCl treated sugar beet leaves revealed that a bHLH TF, BvbHLH93, was significantly increased under salt stress. The BvbHLH93 protein localized in the nucleus and exhibited activation activity. The expression of BvbHLH93 was significantly up-regulated in roots and leaves by salt stress, and the highest expression level in roots and leaves was 24 and 48 h after salt stress, respectively. Furthermore, constitutive expression of BvbHLH93 conferred enhanced salt tolerance in Arabidopsis, as indicated by longer roots and higher content of chlorophyll than wild type. Additionally, the ectopic expression lines accumulated less Na+ and MDA, but more K+ than the WT. Overexpression of the BvBHLH93 enhanced the activities of antioxidant enzymes by positively regulating the expression of antioxidant genes SOD and POD. Compared to WT, the overexpression plants also had low expression levels of RbohD and RbohF, which are involved in reactive oxygen species (ROS) production. These results suggest that BvbHLH93 plays a key role in enhancing salt stress tolerance by enhancing antioxidant enzymes and decreasing ROS generation. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Transcriptome Analysis Unravels Key Factors Involved in Response to Potassium Deficiency and Feedback Regulation of K+ Uptake in Cotton Roots
Int. J. Mol. Sci. 2021, 22(6), 3133; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22063133 - 19 Mar 2021
Viewed by 291
Abstract
To properly understand cotton responses to potassium (K+) deficiency and how its shoot feedback regulates K+ uptake and root growth, we analyzed the changes in root transcriptome induced by low K+ (0.03 mM K+, lasting three days) [...] Read more.
To properly understand cotton responses to potassium (K+) deficiency and how its shoot feedback regulates K+ uptake and root growth, we analyzed the changes in root transcriptome induced by low K+ (0.03 mM K+, lasting three days) in self-grafts of a K+ inefficient cotton variety (CCRI41/CCRI41, scion/rootstock) and its reciprocal grafts with a K+ efficient variety (SCRC22/CCRI41). Compared with CCRI41/CCRI41, the SCRC22 scion enhanced the K+ uptake and root growth of CCRI41 rootstock. A total of 1968 and 2539 differently expressed genes (DEGs) were identified in the roots of CCRI41/CCRI41 and SCRC22/CCRI41 in response to K+ deficiency, respectively. The overlapped and similarly (both up- or both down-) regulated DEGs in the two grafts were considered the basic response to K+ deficiency in cotton roots, whereas the DEGs only found in SCRC22/CCRI41 (1954) and those oppositely (one up- and the other down-) regulated in the two grafts might be the key factors involved in the feedback regulation of K+ uptake and root growth. The expression level of four putative K+ transporter genes (three GhHAK5s and one GhKUP3) increased in both grafts under low K+, which could enable plants to cope with K+ deficiency. In addition, two ethylene response factors (ERFs), GhERF15 and GhESE3, both down-regulated in the roots of CCRI41/CCRI41 and SCRC22/CCRI41, may negatively regulate K+ uptake in cotton roots due to higher net K+ uptake rate in their virus-induced gene silencing (VIGS) plants. In terms of feedback regulation of K+ uptake and root growth, several up-regulated DEGs related to Ca2+ binding and CIPK (CBL-interacting protein kinases), one up-regulated GhKUP3 and several up-regulated GhNRT2.1s probably play important roles. In conclusion, these results provide a deeper insight into the molecular mechanisms involved in basic response to low K+ stress in cotton roots and feedback regulation of K+ uptake, and present several low K+ tolerance-associated genes that need to be further identified and characterized. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Quantitative Analysis of UV-B Radiation Interception in 3D Plant Structures and Intraindividual Distribution of Phenolic Contents
Int. J. Mol. Sci. 2021, 22(5), 2701; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22052701 - 07 Mar 2021
Viewed by 446
Abstract
Ultraviolet-B (UV-B) acts as a regulatory stimulus, inducing the dose-dependent biosynthesis of phenolic compounds such as flavonoids at the leaf level. However, the heterogeneity of biosynthesis activation generated within a whole plant is not fully understood until now and cannot be interpreted without [...] Read more.
Ultraviolet-B (UV-B) acts as a regulatory stimulus, inducing the dose-dependent biosynthesis of phenolic compounds such as flavonoids at the leaf level. However, the heterogeneity of biosynthesis activation generated within a whole plant is not fully understood until now and cannot be interpreted without quantification of UV-B radiation interception. In this study, we analyzed the spatial UV-B radiation interception of kales (Brassica oleracea L. var. Acephala) grown under supplemental UV-B LED using ray-tracing simulation with 3-dimension-scanned models and leaf optical properties. The UV-B-induced phenolic compounds and flavonoids accumulated more, with higher UV-B interception and younger leaves. To distinguish the effects of UV-B energy and leaf developmental age, the contents were regressed separately and simultaneously. The effect of intercepted UV-B on flavonoid content was 4.9-fold that of leaf age, but the effects on phenolic compound biosynthesis were similar. This study confirmed the feasibility and relevance of UV-B radiation interception analysis and paves the way to explore the physical and physiological base determining the intraindividual distribution of phenolic compound in controlled environments. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Functional Characteristics Analysis of Dehydrins in Larix kaempferi under Osmotic Stress
Int. J. Mol. Sci. 2021, 22(4), 1715; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22041715 - 09 Feb 2021
Viewed by 559
Abstract
Dehydrins (DHN) belong to the late embryogenesis abundant II family and have been found to enhance plant tolerance to abiotic stress. In the present study, we reported four DHNs in Larix kaempferi (LkDHN) which were identified from the published transcriptome. Alignment analysis showed [...] Read more.
Dehydrins (DHN) belong to the late embryogenesis abundant II family and have been found to enhance plant tolerance to abiotic stress. In the present study, we reported four DHNs in Larix kaempferi (LkDHN) which were identified from the published transcriptome. Alignment analysis showed that these four LkDHNs shared close relationships and belonged to SK3-type DHNs. The electrophoretic mobility shift assay indicated that these four LkDHNs all possess sequence-independent binding capacity for double-strands DNAs. The subcellular localizations of the four LkDHNs were in both the nucleus and cytoplasm, indicating that these LkDHNs enter the nucleus to exert the ability to bind DNA. The preparation of tobacco protoplasts with different concentrations of mannitol showed that LkDHNs enhanced the tolerance of plant cells under osmotic stress. The overexpression of LkDHNs in yeasts enhanced their tolerance to osmotic stress and helped the yeasts to survive severe stress. In addition, LkDHNs in the nucleus of salt treated tobacco increased. All of these results indicated that the four LkDHNs help plants survive from heavy stress by participating in DNA protection. These four LKDHNs played similar roles in the response to osmotic stress and assisted in the adaptation of L. kaempferi to the arid and cold winter of northern China. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Effect of RIP Overexpression on Abiotic Stress Tolerance and Development of Rice
Int. J. Mol. Sci. 2021, 22(3), 1434; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22031434 - 01 Feb 2021
Viewed by 555
Abstract
Ribosome-inactivating proteins (RIPs) are a class of cytotoxic enzymes that can inhibit protein translation by depurinating rRNA. Most plant RIPs are synthesized with a leader sequence that sequesters the proteins to a cell compartment away from the host ribosomes. However, several rice RIPs [...] Read more.
Ribosome-inactivating proteins (RIPs) are a class of cytotoxic enzymes that can inhibit protein translation by depurinating rRNA. Most plant RIPs are synthesized with a leader sequence that sequesters the proteins to a cell compartment away from the host ribosomes. However, several rice RIPs lack these signal peptides suggesting they reside in the cytosol in close proximity to the plant ribosomes. This paper aims to elucidate the physiological function of two nucleocytoplasmic RIPs from rice, in particular, the type 1 RIP referred to as OsRIP1 and a presumed type 3 RIP called nuRIP. Transgenic rice lines overexpressing these RIPs were constructed and studied for developmental effects resulting from this overexpression under greenhouse conditions. In addition, the performance of transgenic seedlings in response to drought, salt, abscisic acid and methyl jasmonate treatment was investigated. Results suggest that both RIPs can affect methyl jasmonate mediated stress responses. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Transcriptomics Reveals Fast Changes in Salicylate and Jasmonate Signaling Pathways in Shoots of Carbonate-Tolerant Arabidopsis thaliana under Bicarbonate Exposure
Int. J. Mol. Sci. 2021, 22(3), 1226; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22031226 - 27 Jan 2021
Viewed by 518
Abstract
High bicarbonate concentrations of calcareous soils with high pH can affect crop performance due to different constraints. Among these, Fe deficiency has mostly been studied. The ability to mobilize sparingly soluble Fe is a key factor for tolerance. Here, a comparative transcriptomic analysis [...] Read more.
High bicarbonate concentrations of calcareous soils with high pH can affect crop performance due to different constraints. Among these, Fe deficiency has mostly been studied. The ability to mobilize sparingly soluble Fe is a key factor for tolerance. Here, a comparative transcriptomic analysis was performed with two naturally selected Arabidopsis thaliana demes, the carbonate-tolerant A1(c+) and the sensitive T6(c−). Analyses of plants exposed to either pH stress alone (pH 5.9 vs. pH 8.3) or to alkalinity caused by 10 mM NaHCO3 (pH 8.3) confirmed better growth and nutrient homeostasis of A1(c+) under alkaline conditions. RNA-sequencing (RNA-seq) revealed that bicarbonate quickly (3 h) induced Fe deficiency-related genes in T6(c−) leaves. Contrastingly, in A1(c+), initial changes concerned receptor-like proteins (RLP), jasmonate (JA) and salicylate (SA) pathways, methionine-derived glucosinolates (GS), sulfur starvation, starch degradation, and cell cycle. Our results suggest that leaves of carbonate-tolerant plants do not sense iron deficiency as fast as sensitive ones. This is in line with a more efficient Fe translocation to aerial parts. In A1(c+) leaves, the activation of other genes related to stress perception, signal transduction, GS, sulfur acquisition, and cell cycle precedes the induction of iron homeostasis mechanisms yielding an efficient response to bicarbonate stress. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Whole-Transcriptome RNA Sequencing Reveals the Global Molecular Responses and CeRNA Regulatory Network of mRNAs, lncRNAs, miRNAs and circRNAs in Response to Salt Stress in Sugar Beet (Beta vulgaris)
Int. J. Mol. Sci. 2021, 22(1), 289; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22010289 - 30 Dec 2020
Viewed by 607
Abstract
Sugar beet is an important sugar-yielding crop with some tolerance to salt, but the mechanistic basis of this tolerance is not known. In the present study, we have used whole-transcriptome RNA-seq and degradome sequencing in response to salt stress to uncover differentially expressed [...] Read more.
Sugar beet is an important sugar-yielding crop with some tolerance to salt, but the mechanistic basis of this tolerance is not known. In the present study, we have used whole-transcriptome RNA-seq and degradome sequencing in response to salt stress to uncover differentially expressed (DE) mRNAs, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) in both leaves and roots. A competitive endogenous RNA (ceRNA) network was constructed with the predicted DE pairs, which revealed regulatory roles under salt stress. A functional analysis suggests that ceRNAs are implicated in copper redistribution, plasma membrane permeability, glycometabolism and energy metabolism, NAC transcription factor and the phosphoinositol signaling system. Overall, we conducted for the first time a full transcriptomic analysis of sugar beet under salt stress that involves a potential ceRNA network, thus providing a basis to study the potential functions of lncRNAs/circRNAs. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Compensation Mechanism of the Photosynthetic Apparatus in Arabidopsis thaliana ch1 Mutants
Int. J. Mol. Sci. 2021, 22(1), 221; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22010221 - 28 Dec 2020
Viewed by 411
Abstract
The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the [...] Read more.
The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the main aim of this study was to find the strategy in plants for compensation of low chlorophyll content by characterizing and comparing the performance and spectral properties of the photosynthetic apparatus related to the lipid and protein composition in four selected Arabidopsis ch1 mutants and two Arabidopsis ecotypes. Mutation in different loci of the CAO gene, viz., NW41, ch1.1, ch1.2 and ch1.3, manifested itself in a distinct chlorina phenotype, pigment and photosynthetic protein composition. Changes in the CAO mRNA levels and chlorophyllide a (Chlide a) content in ecotypes and ch1 mutants indicated their significant role in the adjustment mechanism of the photosynthetic apparatus to low-light conditions. Exposure of mutants with a lower chlorophyll b content to short-term (1LL) and long-term low-light stress (10LL) enabled showing a shift in the structure of the PSI and PSII complexes via spectral analysis and the thylakoid composition studies. We demonstrated that both ecotypes, Col-1 and Ler-0, reacted to high-light (HL) conditions in a way remarkably resembling the response of ch1 mutants to normal (NL) conditions. We also presented possible ways of regulating the conversion of chlorophyll a to b depending on the type of light stress conditions. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Reducing Flower Competition for Assimilates by Half Results in Higher Yield of Fagopyrum esculentum
Int. J. Mol. Sci. 2020, 21(23), 8953; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21238953 - 25 Nov 2020
Viewed by 522
Abstract
Despite abundant flowering throughout the season, common buckwheat develops a very low number of kernels probably due to competition for assimilates. We hypothesized that plants with a shorter flowering period may give a higher seed yield. To verify the hypothesis, we studied nutrient [...] Read more.
Despite abundant flowering throughout the season, common buckwheat develops a very low number of kernels probably due to competition for assimilates. We hypothesized that plants with a shorter flowering period may give a higher seed yield. To verify the hypothesis, we studied nutrient stress in vitro and in planta and analyzed different embryological and yield parameters, including hormone profile in the flowers. In vitro cultivated flowers on media with strongly reduced nutrient content demonstrated a drastic increase in degenerated embryo sacs. In in planta experiments, where 50% or 75% of flowers or all lateral ramifications were removed, the reduction of the flower competition by half turned out to be the most promising treatment for improving yield. This treatment increased the frequency of properly developed embryo sacs, the average number of mature seeds per plant, and their mass. Strong seed compensation under 50% inflorescence removal could result from increased production of salicylic and jasmonic acid that both favor more effective pollinator attraction. Plants in single-shoot cultivation finished their vegetation earlier, and they demonstrated greater single seed mass per plant than in control. This result suggests that plants of common buckwheat with shorter blooming period could deliver higher seed yield. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Wild Soybean Oxalyl-CoA Synthetase Degrades Oxalate and Affects the Tolerance to Cadmium and Aluminum Stresses
Int. J. Mol. Sci. 2020, 21(22), 8869; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21228869 - 23 Nov 2020
Viewed by 559
Abstract
Acyl activating enzyme 3 (AAE3) was identified as being involved in the acetylation pathway of oxalate degradation, which regulates the responses to biotic and abiotic stresses in various higher plants. Here, we investigated the role of Glycine sojaAAE3 (GsAAE3) in [...] Read more.
Acyl activating enzyme 3 (AAE3) was identified as being involved in the acetylation pathway of oxalate degradation, which regulates the responses to biotic and abiotic stresses in various higher plants. Here, we investigated the role of Glycine sojaAAE3 (GsAAE3) in Cadmium (Cd) and Aluminum (Al) tolerances. The recombinant GsAAE3 protein showed high activity toward oxalate, with a Km of 105.10 ± 12.30 μM and Vmax of 12.64 ± 0.34 μmol min−1 mg−1 protein, suggesting that it functions as an oxalyl–CoA synthetase. The expression of a GsAAE3–green fluorescent protein (GFP) fusion protein in tobacco leaves did not reveal a specific subcellular localization pattern of GsAAE3. An analysis of the GsAAE3 expression pattern revealed an increase in GsAAE3 expression in response to Cd and Al stresses, and it is mainly expressed in root tips. Furthermore, oxalate accumulation induced by Cd and Al contributes to the inhibition of root growth in wild soybean. Importantly, GsAAE3 overexpression increases Cd and Al tolerances in A. thaliana and soybean hairy roots, which is associated with a decrease in oxalate accumulation. Taken together, our data provide evidence that the GsAAE3-encoded protein plays an important role in coping with Cd and Al stresses. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Metal Homeostasis and Gas Exchange Dynamics in Pisum sativum L. Exposed to Cerium Oxide Nanoparticles
Int. J. Mol. Sci. 2020, 21(22), 8497; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21228497 - 11 Nov 2020
Viewed by 511
Abstract
Cerium dioxide nanoparticles are pollutants of emerging concern. They are rarely immobilized in the environment. This study extends our work on Pisum sativum L. as a model plant, cultivated worldwide, and is well suited for investigating additive interactions induced by nanoceria. Hydroponic cultivation, [...] Read more.
Cerium dioxide nanoparticles are pollutants of emerging concern. They are rarely immobilized in the environment. This study extends our work on Pisum sativum L. as a model plant, cultivated worldwide, and is well suited for investigating additive interactions induced by nanoceria. Hydroponic cultivation, which prompts accurate plant growth control and three levels of CeO2 supplementation, were applied, namely, 100, 200, and 500 mg (Ce)/L. Phytotoxicity was estimated by fresh weights and photosynthesis parameters. Additionally, Ce, Cu, Zn, Mn, Fe, Ca, and Mg contents were analyzed by high-resolution continuum source atomic absorption and inductively coupled plasma optical emission techniques. Analysis of variance has proved that CeO2 nanoparticles affected metals uptake. In the roots, it decreased for Cu, Zn, Mn, Fe, and Mg, while a reversed process was observed for Ca. The latter is absorbed more intensively, but translocation to above-ground parts is hampered. At the same time, nanoparticulate CeO2 reduced Cu, Zn, Mn, Fe, and Ca accumulation in pea shoots. The lowest Ce concentration boosted the photosynthesis rate, while the remaining treatments did not induce significant changes. Plant growth stimulation was observed only for the 100 mg/L. To our knowledge, this is the first study that demonstrates the effect of nanoceria on photosynthesis-related parameters in peas. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Growth and Photosynthetic Activity of Selected Spelt Varieties (Triticum aestivum ssp. spelta L.) Cultivated under Drought Conditions with Different Endophytic Core Microbiomes
Int. J. Mol. Sci. 2020, 21(21), 7987; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21217987 - 27 Oct 2020
Viewed by 546
Abstract
The role of the microbiome in the root zone is critically important for plants. However, the mechanism by which plants can adapt to environmental constraints, especially water deficit, has not been fully investigated to date, while the endophytic core microbiome of the roots [...] Read more.
The role of the microbiome in the root zone is critically important for plants. However, the mechanism by which plants can adapt to environmental constraints, especially water deficit, has not been fully investigated to date, while the endophytic core microbiome of the roots of spelt (Triticum aestivum ssp. spelta L.) grown under drought conditions has received little attention. In this study, we hypothesize that differences in the endophytic core of spelt and common wheat root microbiomes can explain the variations in the growth and photosynthetic activity of those plants, especially under drought conditions. Our greenhouse experimental design was completely randomized in a 2 × 4 × 3 factorial scheme: two water regime levels (well-watered and drought), three spelt varieties (T. aestivum ssp. spelta L.: ‘Badenstern’, ‘Badenkrone’ and ‘Zollernspelz’ and one wheat variety: T. aestivum ssp. vulgare L: ‘Dakotana’) and three mycorrhizal levels (autoclaved soil inoculation with Rhizophagus irregularis, control (autoclaved soil) and natural inoculation (non-autoclaved soil—microorganisms from the field). During the imposed stress period, relative water content (RWC), leaf chlorophyll fluorescence, gas exchange and water use efficiency (WUE) were measured. Microscopic observations of the root surface through fungi isolation and identification were conducted. Our results indicate that ‘Badenstern’ was the most drought tolerant variety, followed by ‘Zollernspelz’ and ‘Badenkrone,’ while the common wheat variety ‘Dakotana’ was the most drought sensitive. Inoculation of ‘Badenstern’ with the mycorrhizal fungi R. irregularis contributed to better growth performance as evidenced by increased whole plant and stalk dry matter accumulation, as well as greater root length and volume. Inoculation of ‘Zollernspelz’ with arbuscular mycorrhizal fungi (AMF) enhanced the photochemical efficiency of Photosystem II and significantly improved root growth under drought conditions, which was confirmed by enhanced aboveground biomass, root dry weight and length. This study provides evidence that AMF have the potential to be beneficial for plant growth and dry matter accumulation in spelt varieties grown under drought conditions. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
The Grapevine Calmodulin-Like Protein Gene CML21 Is Regulated by Alternative Splicing and Involved in Abiotic Stress Response
Int. J. Mol. Sci. 2020, 21(21), 7939; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21217939 - 26 Oct 2020
Cited by 2 | Viewed by 575
Abstract
Calmodulin-like proteins (CMLs) represent a large family of plant calcium sensor proteins involved in the regulation of plant responses to environmental cues and developmental processes. In the present work, we identified four alternatively spliced mRNA forms of the grapevine CML21 gene that encoded [...] Read more.
Calmodulin-like proteins (CMLs) represent a large family of plant calcium sensor proteins involved in the regulation of plant responses to environmental cues and developmental processes. In the present work, we identified four alternatively spliced mRNA forms of the grapevine CML21 gene that encoded proteins with distinct N-terminal regions. We studied the transcript abundance of CML21v1, CML21v2, CML21v3, and CML21v4 in wild-growing grapevine Vitis amurensis Rupr. in response to desiccation, heat, cold, high salinity, and high mannitol stress using quantitative real-time RT-PCR. The levels of all four splice variants of VaCML21 were highly induced in response to cold stress. In addition, VaCML21v1 and VaCML21v2 forms were highly modulated by all other abiotic stress treatments. Constitutive expression of VaCML21v2 and VaCML21v4 improved biomass accumulation of V. amurensis callus cell cultures under prolonged low temperature stress. Heterologous expression of the grapevine CML21v2 and VaCML21v4 splice variants in Arabidopsis improved survival rates of the transgenic plants after freezing. The VaCML21v2 overexpression enhanced activation of the cold stress-responsive marker genes AtDREB1A and AtDREB2A, while VaCML21v4 overexpression—AtCOR47, AtRD29A, AtRD29B, and AtKIN1 genes after freezing stress in the transgenic Arabidopsis. The results indicate that the grapevine CML21 gene acts as a positive regulator in the plant response to cold stress. The detected variety of CML21 transcripts and their distinct transcriptional responses suggested that this expansion of mRNA variants could contribute to the diversity of grapevine adaptive reactions. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Molecular Mechanisms Underlying Sugarcane Response to Aluminum Stress by RNA-Seq
Int. J. Mol. Sci. 2020, 21(21), 7934; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21217934 - 26 Oct 2020
Viewed by 649
Abstract
Some metals are beneficial to plants and contribute to critical physiological processes. Some metals, however, are not. The presence of aluminum ions (Al3+) can be very toxic, especially in acidic soils. Considerable parts of the world’s arable land are acidic in [...] Read more.
Some metals are beneficial to plants and contribute to critical physiological processes. Some metals, however, are not. The presence of aluminum ions (Al3+) can be very toxic, especially in acidic soils. Considerable parts of the world’s arable land are acidic in nature; mechanistically elucidating a plant’s response to aluminum stress is critical to mitigating this stress and improving the quality of plants. To identify the genes involved in sugarcane response to aluminum stress, we generated 372 million paired-end RNA sequencing reads from the roots of CTC-2 and RB855453, which are two contrasting cultivars. Data normalization resulted in 162,161 contigs (contiguous sequences) and 97,335 genes from a de novo transcriptome assembly (trinity genes). A total of 4858 and 1307 differently expressed genes (DEGs) for treatment versus control were identified for the CTC-2 and RB855453 cultivars, respectively. The DEGs were annotated into 34 functional categories. The majority of the genes were upregulated in the CTC-2 (tolerant cultivar) and downregulated in RB855453 (sensitive cultivar). Here, we present the first root transcriptome of sugarcane under aluminum stress. The results and conclusions of this study are a crucial launch pad for future genetic and genomic studies of sugarcane. The transcriptome analysis shows that sugarcane tolerance to aluminum may be explained by an efficient detoxification mechanism combined with lateral root formation and activation of redox enzymes. We also present a hypothetical model for aluminum tolerance in the CTC-2 cultivar. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Precise Editing of the OsPYL9 Gene by RNA-Guided Cas9 Nuclease Confers Enhanced Drought Tolerance and Grain Yield in Rice (Oryza sativa L.) by Regulating Circadian Rhythm and Abiotic Stress Responsive Proteins
Int. J. Mol. Sci. 2020, 21(21), 7854; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21217854 - 23 Oct 2020
Cited by 3 | Viewed by 705
Abstract
Abscisic acid (ABA) is involved in regulating drought tolerance, and pyrabactin resistance-like (PYL) proteins are known as ABA receptors. To elucidate the role of one of the ABA receptors in rice, OsPYL9 was mutagenized through CRISPR/Cas9 in rice. Homozygous and heterozygous mutant plants [...] Read more.
Abscisic acid (ABA) is involved in regulating drought tolerance, and pyrabactin resistance-like (PYL) proteins are known as ABA receptors. To elucidate the role of one of the ABA receptors in rice, OsPYL9 was mutagenized through CRISPR/Cas9 in rice. Homozygous and heterozygous mutant plants lacking any off-targets and T-DNA were screened based on site-specific sequencing and used for morpho-physiological, molecular, and proteomic analysis. Mutant lines appear to accumulate higher ABA, antioxidant activities, chlorophyll content, leaf cuticular wax, and survival rate, whereas a lower malondialdehyde level, stomatal conductance, transpiration rate, and vascular bundles occur under stress conditions. Proteomic analysis found a total of 324 differentially expressed proteins (DEPs), out of which 184 and 140 were up and downregulated, respectively. The OsPYL9 mutants showed an increase in grain yield under both drought and well watered field conditions. Most of the DEPs related to circadian clock rhythm, drought response, and reactive oxygen species were upregulated in the mutant plants. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that DEPs were only involved in circadian rhythm and Gene Ontology (GO) analysis showed that most of the DEPs were involved in response to abiotic stimulus, and abscisic acid-activated signaling pathways. Protein GIGANTEA, Adagio-like, and Pseudo-response regulator proteins showed higher interaction in protein–protein interaction (PPI) network. Thus, the overall results showed that CRISPR/Cas9-generated OsPYL9 mutants have potential to improve both drought tolerance and the yield of rice. Furthermore, global proteome analysis provides new potential biomarkers and understandings of the molecular mechanism of rice drought tolerance. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Genome-Wide Identification of the Gossypium hirsutum NHX Genes Reveals That the Endosomal-Type GhNHX4A Is Critical for the Salt Tolerance of Cotton
Int. J. Mol. Sci. 2020, 21(20), 7712; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21207712 - 18 Oct 2020
Cited by 2 | Viewed by 795
Abstract
Soil salinization, which is primarily due to excessive Na+ levels, is a major abiotic stress adversely affecting plant growth and development. The Na+/H+ antiporter (NHX) is a transmembrane protein mediating the transport of Na+ or K+ and [...] Read more.
Soil salinization, which is primarily due to excessive Na+ levels, is a major abiotic stress adversely affecting plant growth and development. The Na+/H+ antiporter (NHX) is a transmembrane protein mediating the transport of Na+ or K+ and H+ across the membrane to modulate the ionic balance of plants in response to salt stress. Research regarding NHXs has mainly focused on the vacuolar-type NHX family members. However, the biological functions of the endosomal-type NHXs remain relatively uncharacterized. In this study, 22 NHX family members were identified in Gossypium hirsutum. A phylogenetic analysis divided the GhNHX genes into two categories, with 18 and 4 in the vacuolar and endosomal groups, respectively. The chromosomal distribution of the NHX genes revealed the significant impact of genome-wide duplication during the polyploidization process on the number of GhNHX genes. Analyses of gene structures and conserved motifs indicated that GhNHX genes in the same phylogenetic cluster are conserved. Additionally, the salt-induced expression patterns confirmed that the expression levels of most of the GhNHX genes are affected by salinity. Specifically, in the endosomal group, GhNHX4A expression was substantially up-regulated by salt stress. A yeast functional complementation test proved that GhNHX4A can partially restore the salt tolerance of the salt-sensitive yeast mutant AXT3. Silencing GhNHX4A expression decreased the resistance of cotton to salt stress because of an increase in the accumulation of Na+ in stems and a decrease in the accumulation of K+ in roots. The results of this study may provide the basis for an in-depth characterization of the regulatory functions of NHX genes related to cotton salt tolerance, especially the endosomal-type GhNHX4A. Furthermore, the presented data may be useful for selecting appropriate candidate genes for the breeding of new salt-tolerant cotton varieties. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
The Anaerobic Product Ethanol Promotes Autophagy-Dependent Submergence Tolerance in Arabidopsis
Int. J. Mol. Sci. 2020, 21(19), 7361; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21197361 - 05 Oct 2020
Cited by 1 | Viewed by 898
Abstract
In response to hypoxia under submergence, plants switch from aerobic respiration to anaerobic fermentation, which leads to the accumulation of the end product, ethanol. We previously reported that Arabidopsis thaliana autophagy-deficient mutants show increased sensitivity to ethanol treatment, indicating that ethanol is likely [...] Read more.
In response to hypoxia under submergence, plants switch from aerobic respiration to anaerobic fermentation, which leads to the accumulation of the end product, ethanol. We previously reported that Arabidopsis thaliana autophagy-deficient mutants show increased sensitivity to ethanol treatment, indicating that ethanol is likely involved in regulating the autophagy-mediated hypoxia response. Here, using a transcriptomic analysis, we identified 3909 genes in Arabidopsis seedlings that were differentially expressed in response to ethanol treatment, including 2487 upregulated and 1422 downregulated genes. Ethanol treatment significantly upregulated genes involved in autophagy and the detoxification of reactive oxygen species. Using transgenic lines expressing AUTOPHAGY-RELATED PROTEIN 8e fused to green fluorescent protein (GFP-ATG8e), we confirmed that exogenous ethanol treatment promotes autophagosome formation in vivo. Phenotypic analysis showed that deletions in the alcohol dehydrogenase gene in adh1 mutants result in attenuated submergence tolerance, decreased accumulation of ATG proteins, and diminished submergence-induced autophagosome formation. Compared to the submergence-tolerant Arabidopsis accession Columbia (Col-0), the submergence-intolerant accession Landsberg erecta (Ler) displayed hypersensitivity to ethanol treatment; we linked these phenotypes to differences in the functions of ADH1 and the autophagy machinery between these accessions. Thus, ethanol promotes autophagy-mediated submergence tolerance in Arabidopsis. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Identification of the Cytosolic Glucose-6-Phosphate Dehydrogenase Gene from Strawberry Involved in Cold Stress Response
Int. J. Mol. Sci. 2020, 21(19), 7322; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21197322 - 03 Oct 2020
Cited by 1 | Viewed by 492
Abstract
Glucose-6-phosphate dehydrogenase (G6PDH) plays an important role in plant stress responses. Here, five FaG6PDH sequences were obtained in strawberry, designated as FaG6PDH-CY, FaG6PDH-P1, FaG6PDH-P1.1, FaG6PDH-P2 and FaG6PDH-P0, which were divided into cytosolic (CY) and plastidic (P) isoforms based on [...] Read more.
Glucose-6-phosphate dehydrogenase (G6PDH) plays an important role in plant stress responses. Here, five FaG6PDH sequences were obtained in strawberry, designated as FaG6PDH-CY, FaG6PDH-P1, FaG6PDH-P1.1, FaG6PDH-P2 and FaG6PDH-P0, which were divided into cytosolic (CY) and plastidic (P) isoforms based on the bioinformatic analysis. The respective FaG6PDH genes had distinct expression patterns in all tissues and at different stages of fruit development. Notably, FaG6PDH-CY was the most highly expressed gene among five FaG6PDH members, indicating it encoded the major G6PDH isoform throughout the plant. FaG6PDH positively regulated cold tolerance in strawberry. Inhibition of its activity gave rise to greater cold-induced injury in plant. The FaG6PDH-CY transcript had a significant increase under cold stress, similar to the G6PDH enzyme activity, suggesting a principal participant in response to cold stress. Further study showed that the low-temperature responsiveness (LTR) element in FaG6PDH-CY promoter can promote the gene expression when plant encountered cold stimuli. Besides, FaG6PDH-CY was involved in regulating cold-induced activation of antioxidant enzyme genes (FaSOD, FaCAT, FaAPX and FaGR) and RBOH-dependent ROS generation. The elevated FaG6PDH-CY enhanced ROS-scavenging capability of antioxidant enzymes to suppress ROS excessive accumulation and relieved the oxidative damage, eventually improving the strawberry resistance to cold stress. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Production of Antioxidant Molecules in Polygonum aviculare (L.) and Senecio vulgaris (L.) under Metal Stress: A Possible Tool in the Evaluation of Plant Metal Tolerance
Int. J. Mol. Sci. 2020, 21(19), 7317; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21197317 - 03 Oct 2020
Viewed by 491
Abstract
Plants growing on heavy metal (HM)-polluted soils show toxicity symptoms, such as chlorosis and growth reduction, and undergo oxidative stress due to the formation of reactive oxygen species (ROS). Plants overcome oxidative stress by producing a wide range of antioxidant molecules, such as [...] Read more.
Plants growing on heavy metal (HM)-polluted soils show toxicity symptoms, such as chlorosis and growth reduction, and undergo oxidative stress due to the formation of reactive oxygen species (ROS). Plants overcome oxidative stress by producing a wide range of antioxidant molecules, such as polyphenols and flavonoids. The aim of the present work was to study the accumulation of these molecules in response to increasing concentrations of Cd, Cr, Cu, Ni, Pb and Zn and to assess whether they can be used as a tool in assessing metal-related stress in Polygonum aviculare and Senecio vulgaris. On average, P. aviculare shoots accumulated lower amounts of metals than S. vulgaris shoots. The uptake of all six elements was correlated and proportional to their concentration in the nutrient solution (ρ > 0.9), with the bioaccumulation factor (BAF) being >1 for most of them. The present research demonstrated that 82% of the samples showed a good correlation (|ρ| > 0.5) between the level of polyphenols, flavonoids and antioxidant activity and the metal concentration in plant shoots, confirming that the metal stress level and production of phenolic compounds having antioxidant activity were strictly connected. Nonetheless, the mere quantification of these molecules cannot identify the type of metal that caused the oxidative stress, neither determine the concentration of the stressors. The five tested populations of each species did not show any specific adaptation to the environment of origin. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Overexpression of UGT74E2, an Arabidopsis IBA Glycosyltransferase, Enhances Seed Germination and Modulates Stress Tolerance via ABA Signaling in Rice
Int. J. Mol. Sci. 2020, 21(19), 7239; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21197239 - 30 Sep 2020
Viewed by 585
Abstract
UDP-glycosyltransferases (UGTs) play key roles in modulating plant development and responses to environmental challenges. Previous research reported that the Arabidopsis UDP-glucosyltransferase 74E2 (AtUGT74E2), which transfers glucose to indole-3-butyric acid (IBA), is involved in regulating plant architecture and stress responses. Here, we [...] Read more.
UDP-glycosyltransferases (UGTs) play key roles in modulating plant development and responses to environmental challenges. Previous research reported that the Arabidopsis UDP-glucosyltransferase 74E2 (AtUGT74E2), which transfers glucose to indole-3-butyric acid (IBA), is involved in regulating plant architecture and stress responses. Here, we show novel and distinct roles of UGT74E2 in rice. We found that overexpression of AtUGT74E2 in rice could enhance seed germination. This effect was also observed in the presence of IBA and abscisic acid (ABA), as well as salt and drought stresses. Further investigation indicated that the overexpression lines had lower levels of free IBA and ABA compared to wild-type plants. Auxin signaling pathway gene expression such as for OsARF and OsGH3 genes, as well as ABA signaling pathway genes OsABI3 and OsABI5, was substantially downregulated in germinating seeds of UGT74E2 overexpression lines. Consistently, due to reduced IBA and ABA levels, the established seedlings were less tolerant to drought and salt stresses. The regulation of rice seed germination and stress tolerance could be attributed to IBA and ABA level alterations, as well as modulation of the auxin/ABA signaling pathways by UGT74E2. The distinct roles of UGT74E2 in rice implied that complex and different molecular regulation networks exist between Arabidopsis and rice. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
The Interplay between Toxic and Essential Metals for Their Uptake and Translocation Is Likely Governed by DNA Methylation and Histone Deacetylation in Maize
Int. J. Mol. Sci. 2020, 21(18), 6959; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21186959 - 22 Sep 2020
Viewed by 771
Abstract
The persistent nature of lead (Pb) and cadmium (Cd) in the environment severely affects plant growth and yield. Conversely, plants acquire zinc (Zn) from the soil for their vital physiological and biochemical functions. However, the interplay and coordination between essential and toxic metals [...] Read more.
The persistent nature of lead (Pb) and cadmium (Cd) in the environment severely affects plant growth and yield. Conversely, plants acquire zinc (Zn) from the soil for their vital physiological and biochemical functions. However, the interplay and coordination between essential and toxic metals for their uptake and translocation and the putative underlying epigenetic mechanisms have not yet been investigated in maize. Here, we report that the presence of Zn facilitates the accumulation and transport of Pb and Cd in the aerial parts of the maize plants. Moreover, the Zn, Pb, and Cd interplay specifically interferes with the uptake and translocation of other divalent metals, such as calcium and magnesium. Zn, Pb, and Cd, individually and in combinations, differentially regulate the expression of DNA methyltransferases, thus alter the DNA methylation levels at the promoter of Zinc-regulated transporters, Iron-regulated transporter-like Protein (ZIP) genes to regulate their expression. Furthermore, the expression of histone deacetylases (HDACs) varies greatly in response to individual and combined metals, and HDACs expression showed a negative correlation with ZIP transporters. Our study highlights the implication of DNA methylation and histone acetylation in regulating the metal stress tolerance dynamics through Zn transporters and warns against the excessive use of Zn fertilizers in metal contaminated soils. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Drought Disrupts Auxin Localization in Abscission Zone and Modifies Cell Wall Structure Leading to Flower Separation in Yellow Lupine
Int. J. Mol. Sci. 2020, 21(18), 6848; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21186848 - 18 Sep 2020
Viewed by 679
Abstract
Drought causes the excessive abscission of flowers in yellow lupine, leading to yield loss and serious economic consequences in agriculture. The structure that determines the time of flower shedding is the abscission zone (AZ). Its functioning depends on the undisturbed auxin movement from [...] Read more.
Drought causes the excessive abscission of flowers in yellow lupine, leading to yield loss and serious economic consequences in agriculture. The structure that determines the time of flower shedding is the abscission zone (AZ). Its functioning depends on the undisturbed auxin movement from the flower to the stem. However, little is known about the mechanism guiding cell–cell adhesion directly in an AZ under water deficit. Therefore, here, we seek a fuller understanding of drought-dependent reactions and check the hypothesis that water limitation in soil disturbs the natural auxin balance within the AZ and, in this way, modifies the cell wall structure, leading to flower separation. Our strategy combined microscopic, biochemical, and chromatography approaches. We show that drought affects indole-3-acetic acid (IAA) distribution and evokes cellular changes, indicating AZ activation and flower abortion. Drought action was manifested by the accumulation of proline in the AZ. Moreover, cell wall-related modifications in response to drought are associated with reorganization of methylated homogalacturonans (HG) in the AZ, and upregulation of pectin methylesterase (PME) and polygalacturonase (PG)—enzymes responsible for pectin remodeling. Another symptom of stress action is the accumulation of hemicelluloses. Our data provide new insights into cell wall remodeling events during drought-induced flower abscission, which is relevant to control plant production. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Genome-Wide Analysis Reveals Dynamic Epigenomic Differences in Soybean Response to Low-Phosphorus Stress
Int. J. Mol. Sci. 2020, 21(18), 6817; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21186817 - 17 Sep 2020
Viewed by 507
Abstract
Low-phosphorus (low-P) stress has a significant limiting effect on crop yield and quality. Although the molecular mechanisms of the transcriptional level responsible for the low-P stress response have been studied in detail, the underlying epigenetic mechanisms in gene regulation remain largely unknown. In [...] Read more.
Low-phosphorus (low-P) stress has a significant limiting effect on crop yield and quality. Although the molecular mechanisms of the transcriptional level responsible for the low-P stress response have been studied in detail, the underlying epigenetic mechanisms in gene regulation remain largely unknown. In this study, we evaluated the changes in DNA methylation, gene expression and small interfering RNAs (siRNAs) abundance genome-wide in response to low-P stress in two representative soybean genotypes with different P-efficiencies. The DNA methylation levels were slightly higher under low-P stress in both genotypes. Integrative methylation and transcription analysis suggested a complex regulatory relationship between DNA methylation and gene expression that may be associated with the type, region, and extent of methylation. Association analysis of low-P-induced differential methylation and gene expression showed that transcriptional alterations of a small part of genes were associated with methylation changes. Dynamic methylation alterations in transposable element (TE) regions in the CHH methylation context correspond with changes in the amount of siRNA under low-P conditions, indicating an important role of siRNAs in modulating TE activity by guiding CHH methylation in TE regions. Together, these results could help to elucidate the epigenetic regulation mechanisms governing the responses of plants to abiotic stresses. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Functional Characterization of a Putative RNA Demethylase ALKBH6 in Arabidopsis Growth and Abiotic Stress Responses
Int. J. Mol. Sci. 2020, 21(18), 6707; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21186707 - 13 Sep 2020
Viewed by 822
Abstract
RNA methylation and demethylation, which is mediated by RNA methyltransferases (referred to as “writers”) and demethylases (referred to as “erasers”), respectively, are emerging as a key regulatory process in plant development and stress responses. Although several studies have shown that AlkB homolog (ALKBH) [...] Read more.
RNA methylation and demethylation, which is mediated by RNA methyltransferases (referred to as “writers”) and demethylases (referred to as “erasers”), respectively, are emerging as a key regulatory process in plant development and stress responses. Although several studies have shown that AlkB homolog (ALKBH) proteins are potential RNA demethylases, the function of most ALKBHs is yet to be determined. The Arabidopsis thaliana genome contains thirteen genes encoding ALKBH proteins, the functions of which are largely unknown. In this study, we characterized the function of a potential eraser protein, ALKBH6 (At4g20350), during seed germination and seedling growth in Arabidopsis under abiotic stresses. The seeds of T-DNA insertion alkbh6 knockdown mutants germinated faster than the wild-type seeds under cold, salt, or abscisic acid (ABA) treatment conditions but not under dehydration stress conditions. Although no differences in seedling and root growth were observed between the alkbh6 mutant and wild-type under normal conditions, the alkbh6 mutant showed a much lower survival rate than the wild-type under salt, drought, or heat stress. Cotyledon greening of the alkbh6 mutants was much higher than that of the wild-type upon ABA application. Moreover, the transcript levels of ABA signaling-related genes, including ABI3 and ABI4, were down-regulated in the alkbh6 mutant compared to wild-type plants. Importantly, the ALKBH6 protein had an ability to bind to both m6A-labeled and m5C-labeled RNAs. Collectively, these results indicate that the potential eraser ALKBH6 plays important roles in seed germination, seedling growth, and survival of Arabidopsis under abiotic stresses. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
The Metabolic Reprogramming Induced by Sub-Optimal Nutritional and Light Inputs in Soilless Cultivated Green and Red Butterhead Lettuce
Int. J. Mol. Sci. 2020, 21(17), 6381; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21176381 - 02 Sep 2020
Cited by 3 | Viewed by 712
Abstract
Sub-optimal growing conditions have a major effect on plants; therefore, large efforts are devoted to maximizing the availability of agricultural inputs to crops. To increase the sustainable use of non-renewable inputs, attention is currently given to the study of plants under non-optimal conditions. [...] Read more.
Sub-optimal growing conditions have a major effect on plants; therefore, large efforts are devoted to maximizing the availability of agricultural inputs to crops. To increase the sustainable use of non-renewable inputs, attention is currently given to the study of plants under non-optimal conditions. In this work, we investigated the impact of sub-optimal macrocations availability and light intensity in two lettuce varieties that differ for the accumulation of secondary metabolites (i.e., ‘Red Salanova’ and ‘Green Salanova’). Photosynthesis-related measurements and untargeted metabolomics were used to identify responses and pathways involved in stress resilience. The pigmented (‘Red’) and the non-pigmented (‘Green Salanova’) lettuce exhibited distinctive responses to sub-optimal conditions. The cultivar specific metabolomic signatures comprised a broad modulation of metabolism, including secondary metabolites, phytohormones, and membrane lipids signaling cascade. Several stress-related metabolites were altered by either treatment, including polyamines (and other nitrogen-containing compounds), phenylpropanoids, and lipids. The metabolomics and physiological response to macrocations availability and light intensity also implies that the effects of low-input sustainable farming systems should be evaluated considering a range of cultivar-specific positive and disadvantageous metabolic effects in addition to yield and other socio-economic parameters. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Characterization of the Role of SPL9 in Drought Stress Tolerance in Medicago sativa
Int. J. Mol. Sci. 2020, 21(17), 6003; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21176003 - 20 Aug 2020
Viewed by 640
Abstract
Extreme environmental conditions, such as drought, are expected to increase in frequency and severity due to climate change, leading to substantial deficiencies in crop yield and quality. Medicago sativa (alfalfa) is an important crop that is relied upon as a staple source of [...] Read more.
Extreme environmental conditions, such as drought, are expected to increase in frequency and severity due to climate change, leading to substantial deficiencies in crop yield and quality. Medicago sativa (alfalfa) is an important crop that is relied upon as a staple source of forage in ruminant feed. Despite its economic importance, alfalfa production is constrained by abiotic stress, including drought. In this report, we investigate the role of Squamosa Promoter Binding Protein-Like 9 (SPL9), a target of miR156, in drought tolerance. Transgenic alfalfa plants with RNAi-silenced MsSPL9 (SPL9-RNAi) were compared to wild-type (WT) alfalfa for phenotypic changes and drought tolerance indicators. In SPL9-RNAi plants, both stem thickness and plant height were reduced in two- and six-month-old alfalfa, respectively; however, yield was unaffected. SPL9-RNAi plants showed less leaf senescence and had augmented relative water content under drought conditions, indicating that SPL9-RNAi plants had greater drought tolerance potential than WT plants. Interestingly, SPL9-RNAi plants accumulated more stress-alleviating anthocyanin compared to WT under both drought and well-watered control conditions, suggesting that MsSPL9 may contribute to drought tolerance in alfalfa, at least in part, by regulating anthocyanin biosynthesis. The results suggest that targeting MsSPL9 is a suitable means for improving alfalfa resilience towards drought conditions. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
Identification of a Novel Gene, Osbht, in Response to High Temperature Tolerance at Booting Stage in Rice
Int. J. Mol. Sci. 2020, 21(16), 5862; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21165862 - 15 Aug 2020
Cited by 1 | Viewed by 669
Abstract
Rice is one of the world’s leading food crops, and over 90% of the world’s rice production stems from Asia. In particular, an increase of 1 °C in the minimum temperature reduces the quantity of rice by 10%. Therefore, the development of rice [...] Read more.
Rice is one of the world’s leading food crops, and over 90% of the world’s rice production stems from Asia. In particular, an increase of 1 °C in the minimum temperature reduces the quantity of rice by 10%. Therefore, the development of rice varieties that can stably maintain the yield and quality of the rice even under these rapid climate changes is indispensable. In this study, we performed quantitative trait loci (QTL) mapping after treatment with heat stress during the booting stage in rice. We performed a QTL analysis using the Cheongcheong/Nagdong double haploid (CNDH) line and identified 19 QTLs during the 2 year analysis. Of these QTL regions, the 2.2 cM region of RM3709–RM11694 on chromosome 1 was shared among the six traits (heading date; culm length; panicle length; number of tiller; 1000 grain weight; and content of chlorophyll) examined. Rice Microsatellite (RM) 3709–RM11694 contained 27 high-temperature-tolerance candidate genes. Among the candidate genes, OsBHT showed a different gene expression level between CNDH75, which is a high-temperature tolerant line, and CNDH11 which is a susceptible line. Although some existing high-temperature-tolerant genes have been reported, OsBHT can be used more effectively for the development of heat tolerance in rice. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessArticle
The Alleviation of Photosynthetic Damage in Tomato under Drought and Cold Stress by High CO2 and Melatonin
Int. J. Mol. Sci. 2020, 21(15), 5587; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21155587 - 04 Aug 2020
Viewed by 883
Abstract
The atmospheric CO2 concentration (a[CO2]) is increasing at an unprecedented pace. Exogenous melatonin plays positive roles in the response of plants to abiotic stresses, including drought and cold. The effect of elevated CO2 concentration (e[CO2]) accompanied by [...] Read more.
The atmospheric CO2 concentration (a[CO2]) is increasing at an unprecedented pace. Exogenous melatonin plays positive roles in the response of plants to abiotic stresses, including drought and cold. The effect of elevated CO2 concentration (e[CO2]) accompanied by exogenous melatonin on plants under drought and cold stresses remains unknown. Here, tomato plants were grown under a[CO2] and e[CO2], with half of the plants pre-treated with melatonin. The plants were subsequently treated with drought stress followed by cold stress. The results showed that a decreased net photosynthetic rate (PN) was aggravated by a prolonged water deficit. The PN was partially restored after recovery from drought but stayed low under a successive cold stress. Starch content was downregulated by drought but upregulated by cold. The e[CO2] enhanced PN of the plants under non-stressed conditions, and moderate drought and recovery but not severe drought. Stomatal conductance (gs) and the transpiration rate (E) was less inhibited by drought under e[CO2] than under a[CO2]. Tomato grown under e[CO2] had better leaf cooling than under a[CO2] when subjected to drought. Moreover, melatonin enhanced PN during recovery from drought and cold stress, and enhanced biomass accumulation in tomato under e[CO2]. The chlorophyll a content in plants treated with melatonin was higher than in non-treated plants under e[CO2] during cold stress. Our findings will improve the knowledge on plant responses to abiotic stresses in a future [CO2]-rich environment accompanied by exogenous melatonin. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Review

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Open AccessReview
Plant Mitogen-Activated Protein Kinase Cascades in Environmental Stresses
Int. J. Mol. Sci. 2021, 22(4), 1543; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22041543 - 03 Feb 2021
Viewed by 519
Abstract
Due to global warming and population growth, plants need to rescue themselves, especially in unfavorable environments, to fulfill food requirements because they are sessile organisms. Stress signal sensing is a crucial step that determines the appropriate response which, ultimately, determines the survival of [...] Read more.
Due to global warming and population growth, plants need to rescue themselves, especially in unfavorable environments, to fulfill food requirements because they are sessile organisms. Stress signal sensing is a crucial step that determines the appropriate response which, ultimately, determines the survival of plants. As important signaling modules in eukaryotes, plant mitogen-activated protein kinase (MAPK) cascades play a key role in regulating responses to the following four major environmental stresses: high salinity, drought, extreme temperature and insect and pathogen infections. MAPK cascades are involved in responses to these environmental stresses by regulating the expression of related genes, plant hormone production and crosstalk with other environmental stresses. In this review, we describe recent major studies investigating MAPK-mediated environmental stress responses. We also highlight the diverse function of MAPK cascades in environmental stress. These findings help us understand the regulatory network of MAPKs under environmental stress and provide another strategy to improve stress resistance in crops to ensure food security. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessReview
Plant Morphological, Physiological and Anatomical Adaption to Flooding Stress and the Underlying Molecular Mechanisms
Int. J. Mol. Sci. 2021, 22(3), 1088; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms22031088 - 22 Jan 2021
Viewed by 543
Abstract
Globally, flooding is a major threat causing substantial yield decline of cereal crops, and is expected to be even more serious in many parts of the world due to climatic anomaly in the future. Understanding the mechanisms of plants coping with unanticipated flooding [...] Read more.
Globally, flooding is a major threat causing substantial yield decline of cereal crops, and is expected to be even more serious in many parts of the world due to climatic anomaly in the future. Understanding the mechanisms of plants coping with unanticipated flooding will be crucial for developing new flooding-tolerance crop varieties. Here we describe survival strategies of plants adaptation to flooding stress at the morphological, physiological and anatomical scale systemically, such as the formation of adventitious roots (ARs), aerenchyma and radial O2 loss (ROL) barriers. Then molecular mechanisms underlying the adaptive strategies are summarized, and more than thirty identified functional genes or proteins associated with flooding-tolerance are searched out and expounded. Moreover, we elaborated the regulatory roles of phytohormones in plant against flooding stress, especially ethylene and its relevant transcription factors from the group VII Ethylene Response Factor (ERF-VII) family. ERF-VIIs of main crops and several reported ERF-VIIs involving plant tolerance to flooding stress were collected and analyzed according to sequence similarity, which can provide references for screening flooding-tolerant genes more precisely. Finally, the potential research directions in the future were summarized and discussed. Through this review, we aim to provide references for the studies of plant acclimation to flooding stress and breeding new flooding-resistant crops in the future. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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Open AccessReview
Regulation of ROS Metabolism in Plants under Environmental Stress: A Review of Recent Experimental Evidence
Int. J. Mol. Sci. 2020, 21(22), 8695; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21228695 - 18 Nov 2020
Cited by 9 | Viewed by 891
Abstract
Various environmental stresses singly or in combination generate excess amounts of reactive oxygen species (ROS), leading to oxidative stress and impaired redox homeostasis. Generation of ROS is the obvious outcome of abiotic stresses and is gaining importance not only for their ubiquitous generation [...] Read more.
Various environmental stresses singly or in combination generate excess amounts of reactive oxygen species (ROS), leading to oxidative stress and impaired redox homeostasis. Generation of ROS is the obvious outcome of abiotic stresses and is gaining importance not only for their ubiquitous generation and subsequent damaging effects in plants but also for their diversified roles in signaling cascade, affecting other biomolecules, hormones concerning growth, development, or regulation of stress tolerance. Therefore, a good balance between ROS generation and the antioxidant defense system protects photosynthetic machinery, maintains membrane integrity, and prevents damage to nucleic acids and proteins. Notably, the antioxidant defense system not only scavenges ROS but also regulates the ROS titer for signaling. A glut of studies have been executed over the last few decades to discover the pattern of ROS generation and ROS scavenging. Reports suggested a sharp threshold level of ROS for being beneficial or toxic, depending on the plant species, their growth stages, types of abiotic stresses, stress intensity, and duration. Approaches towards enhancing the antioxidant defense in plants is one of the vital areas of research for plant biologists. Therefore, in this review, we accumulated and discussed the physicochemical basis of ROS production, cellular compartment-specific ROS generation pathways, and their possible distressing effects. Moreover, the function of the antioxidant defense system for detoxification and homeostasis of ROS for maximizing defense is also discussed in light of the latest research endeavors and experimental evidence. Full article
(This article belongs to the Special Issue Environmental Stress and Plants)
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