Identification and characterization of MADS-box gene family in pigeonpea, their wild relatives and comparative phylogenetic analysis with grain legumes.

Abstract

MADS-box genes are classes of transcription factors involved in various physiological and developmental processes in plants. Here, genome wide identification of MADS-box genes was done in Cajanus cajan, identifying 102 members, classified into two different groups based on their gene structure. The gene based phylogeny of C. cajan MADS-box genes, and some grain legumes was developed to detect their gene homologs in C. cajan. The status of all these genes was analyzed in three wild relatives i.e. C. scarabaeoides, C. platycarpus and C. cajanifolius. A total of 41 MADS-box genes were found to be missing in wild type cultivars hinting towards their role in domestication and evolution. Single copy of Flowering locus C (FLC) and Short vegetative phase (SVP), while three copies of Suppressor of activation of Constans 1 (SOC1) was found to be present. One SOC1 gene i.e. CcMADS1.5 was found to be missing in all wild relatives, also forming separate clade in phylogeny, revealing its origin through duplication followed by divergence, and role in domestication. Expression profiling of major MADS-box genes involved in flowering was done in different tissues viz vegetative meristem vegetative leaf, reproductive meristem and reproductive bud. Gene based time tree of FLC and SOC1 gene dictates their divergence from Arabidopsis before 71 and 23 million year ago (mya) respectively. This study provides valuable insights into the functions, characteristics and evolution of MADS-box proteins in grain legumes with emphasis on C. cajan, which may help in further characterizing these genes.