Dear Colleagues,

Some soil-dwelling microbes of the α and β classes of proteobacteria, collectively referred to as rhizobia, are well-known for their ability to establish species-specific nitrogen-fixing mutualistic symbioses with legumes. Other diazotrophic bacteria (e.g., Frankia and Cyanobacteria) can also live in symbiosis with a large diversity of non-legume plants. These associations render plant growth independent of the costly and environmentally unfriendly chemical fertilizers, collectively contributing more than half of the combined nitrogen incorporated annually into terrestrial ecosystems. Plant symbiotic diazotrophs have been the focus of intensive research worldwide during recent decades due to their great impact on planet sustainability. Besides, these symbioses represent complex biological experimental models to decipher the underlying fundamental mechanisms of interactions between bacteria and a eukaryotic host. During the last two decades, the development of high-throughput technologies to explore the structure and function of bacterial genomes has revolutionized our understanding of nitrogen-fixing symbioses at a fundamental level, providing new opportunities for a more rational biotechnological exploitation of the different systems. This Special Issue has been conceived to update the most recent insights into the biology of the plant symbiotic nitrogen-fixers from a holistic genomic perspective. The issue will gather review and research articles addressing different aspects of plant symbiotic diazotrophs genomics including but not limited to the following:

• Structure of genomes and pangenomes of the different species
• Population and evolutionary genomics
• Genetic, metabolic and regulatory networks
• The non-coding transcriptome and regulation of gene expression by RNA
• Novel functional genomics approaches to understand plant symbioses
• Genomics-based engineering of bioinoculants and nitrogen-fixation

Dr. José I. Jiménez-Zurdo
Chief Guest Editor
Prof. Dr. Alessio Mengoni
Guest Editors

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