Diversification of cytokinin phosphotransfer signaling genes in Medicago truncatula and other legume genomes

BMC Genomics

Florian Frugier¹  Mathias Brault¹  Sovanna Tan¹  Pascal Gamas²  Frédéric Debellé² 

[1] IPS2 (Institute of Plant Sciences Paris-Saclay), CNRS, Université Paris-Sud, Université Paris-Diderot, INRA, Université d’Evry, Université Paris-Saclay;LIPM, Université de Toulouse, INRA, CNRS;

关键词: Phosphorelay;    Cytokinin signaling;    Histidine kinase;    Response regulator;    Legumes;    Symbiotic nitrogen-fixing nodulation;   

DOI  :  10.1186/s12864-019-5724-z

来源: DOAJ

【 摘 要 】

Abstract Background Legumes can establish on nitrogen-deprived soils a symbiotic interaction with Rhizobia bacteria, leading to the formation of nitrogen-fixing root nodules. Cytokinin phytohormones are critical for triggering root cortical cell divisions at the onset of nodule initiation. Cytokinin signaling is based on a Two-Component System (TCS) phosphorelay cascade, involving successively Cytokinin-binding Histidine Kinase receptors, phosphorelay proteins shuttling between the cytoplasm and the nucleus, and Type-B Response Regulator (RRB) transcription factors activating the expression of cytokinin primary response genes. Among those, Type-A Response Regulators (RRA) exert a negative feedback on the TCS signaling. To determine whether the legume plant nodulation capacity is linked to specific features of TCS proteins, a genome-wide identification was performed in six legume genomes (Cajanus cajan, pigeonpea; Cicer arietinum, chickpea; Glycine max, soybean; Phaseolus vulgaris, common bean; Lotus japonicus; Medicago truncatula). The diversity of legume TCS proteins was compared to the one found in two non-nodulating species, Arabidopsis thaliana and Vitis vinifera, which are references for functional analyses of TCS components and phylogenetic analyses, respectively. Results A striking expansion of non-canonical RRBs was identified, notably leading to the emergence of proteins where the conserved phosphor-accepting aspartate residue is replaced by a glutamate or an asparagine. M. truncatula genome-wide expression datasets additionally revealed that only a limited subset of cytokinin-related TCS genes is highly expressed in different organs, namely MtCHK1/MtCRE1, MtHPT1, and MtRRB3, suggesting that this “core” module potentially acts in most plant organs including nodules. Conclusions Further functional analyses are required to determine the relevance of these numerous non-canonical TCS RRBs in symbiotic nodulation, as well as of canonical MtHPT1 and MtRRB3 core signaling elements.

【 授权许可】

Unknown