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Regulation of Three Key Kinases of Brassinosteroid Signaling Pathway

Characterization of FLOWERING LOCUS C Homologs in Apple as a Model for Fruit Trees

Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 980-8572, Japan
Faculty of Life and Environmental Science, Shimane University, Matsue 690-8504, Japan
Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(12), 4562;
Received: 28 April 2020 / Revised: 22 June 2020 / Accepted: 24 June 2020 / Published: 26 June 2020
(This article belongs to the Special Issue Cell Signaling in Model Plants)
To elucidate the molecular mechanism of juvenility and annual flowering of fruit trees, FLOWERING LOCUS C (FLC), an integrator of flowering signals, was investigated in apple as a model. We performed sequence and expression analyses and transgenic experiments related to juvenility with annual flowering to characterize the apple FLC homologs MdFLC. The phylogenetic tree analysis, which included other MADS-box genes, showed that both MdFLC1 and MdFLC3 belong to the same FLC group. MdFLC1c from one of the MdFLC1 splice variants and MdFLC3 contain the four conserved motives of an MIKC-type MADS protein. The mRNA of variants MdFLC1a and MdFLC1b contain intron sequences, and their deduced amino acid sequences lack K- and C-domains. The expression levels of MdFLC1a, MdFLC1b, and MdFLC1c decreased during the flowering induction period in a seasonal expression pattern in the adult trees, whereas the expression level of MdFLC3 did not decrease during that period. This suggests that MdFLC1 is involved in flowering induction in the annual growth cycle of adult trees. In apple seedlings, because phase change can be observed in individuals, seedlings can be used for analysis of expression during phase transition. The expression levels of MdFLC1b, MdFLC1c, and MdFLC3 were high during the juvenile phase and low during the transitional and adult phases. Because the expression pattern of MdFLC3 suggests that it plays a specific role in juvenility, MdFLC3 was subjected to functional analysis by transformation of Arabidopsis. The results revealed the function of MdFLC3 as a floral repressor. In addition, MdFT had CArG box-like sequences, putative targets for the suppression of flowering by MdFLC binding, in the introns and promoter regions. These results indicate that apple homologs of FLC, which might play a role upstream of the flowering signals, could be involved in juvenility as well as in annual flowering. Apples with sufficient genome-related information are useful as a model for studying phenomena unique to woody plants such as juvenility and annual flowering. View Full-Text
Keywords: Malus domestica; Rosaceae; juvenility; FLOWERING LOCUS C; flowering Malus domestica; Rosaceae; juvenility; FLOWERING LOCUS C; flowering
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MDPI and ACS Style

Kagaya, H.; Ito, N.; Shibuya, T.; Komori, S.; Kato, K.; Kanayama, Y. Characterization of FLOWERING LOCUS C Homologs in Apple as a Model for Fruit Trees. Int. J. Mol. Sci. 2020, 21, 4562.

AMA Style

Kagaya H, Ito N, Shibuya T, Komori S, Kato K, Kanayama Y. Characterization of FLOWERING LOCUS C Homologs in Apple as a Model for Fruit Trees. International Journal of Molecular Sciences. 2020; 21(12):4562.

Chicago/Turabian Style

Kagaya, Hidenao, Naoko Ito, Tomoki Shibuya, Sadao Komori, Kazuhisa Kato, and Yoshinori Kanayama. 2020. "Characterization of FLOWERING LOCUS C Homologs in Apple as a Model for Fruit Trees" International Journal of Molecular Sciences 21, no. 12: 4562.

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