Genome-wide identification, phylogeny, and expression profiling of RWP-RK gene family under low nitrogen and nodulation in Arabidopsis and legumes

Abstract Background Nitrogen, as a constituent of amino acids and nucleic acids, is an essential macronutrient for all living organisms. The nitrogen-fixation clade (NFC) is a clade, consisting of Fabales, Fagales, Cucurbitales, and Rosales, where all nodulating plants have been originated. The plant-specific RWP-RK family of transcription factors are involved in nitrate responses and play specific roles in nodule inception. In the present study, by investigation of RWP-RKs at genome-wide level and comparative coexpression networks, the roles of RWP-RKs involved in nitrate response and nodulation were analyzed to reveal evolution of RWP-RKs and a possible relationship between nitrogen signaling and nodulation.Results Here, we systematically investigated 292 RWP-RKs from 26 species of legumes and non-legumes of NFC by whole-genomic analysis and characterized their evolutionary relationships, protein motifs, and gene structures. We compared RWP-RK networks from Arabidopsis thaliana under N-starvation and N-supplementation conditions, as well as transcriptome atlases from Phaseolus vulgaris and Glycine max . This revealed that N starvation, which is essential for nodulation, alters the connectivity of RWP-RKs to other genes, including symbiosis-related genes. Meanwhile, appropriately low concentrations of nitrates stimulate nodulation by regulating RWP-RK expression in P. vulgaris .Conclusions Our comparative evolutionary analysis of RWP-RKs between A. thaliana and legumes revealed the evolutionary features and the relationship between the nitrate signaling pathway in a model organism and nodulation in legumes.