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MADS box genes are class of transcription factors involved in various physiological and developmental processes in plants. To understand their role in floral transition-related pathways, a genome-wide identification was done in Cajanus cajan , identifying 102 members which were classified into two different groups based on their gene structure. The status of all these genes was further analyzed in three wild species i.e. C. scarabaeoides , C. platycarpus and C. cajanifolius which revealed absence of 31-34 MADS box genes in them hinting towards their role in domestication and evolution. We could locate only a single copy of both FLOWERING LOCUS C ( FLC ) and SHORT VEGETATIVE PHASE ( SVP ) genes, while three paralogs of SUPPRESSOR OF ACTIVATION OF CONSTANS 1 ( SOC1 ) were found in C. cajan genome. One of those SOC1 paralogs i.e. CcMADS1.5 was found to be missing in all three wild relatives, also forming separate clade in phylogeny. This SOC1 gene was also lacking the characteristic MADS box domain in it. Expression profiling of major MADS box genes involved in flowering was done in different tissues viz shoot apical 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 functional characteristics, expression pattern, and evolution of MADS box proteins in grain legumes with emphasis on C. cajan , which may help in further characterizing these genes., Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-020-02605-7., Competing Interests: Conflict of interestAuthors hereby declare that no conflict of interest exists., (© King Abdulaziz City for Science and Technology 2021.)

Understanding the molecular mechanism underlying photoperiod sensitivity will play a crucial role in extending the cropping area of Cajanus cajan, a photoperiod sensitive major grain legume of India and Africa. In flowering plants, Flowering locus T (FT) gene is involved in the production of florigen molecule which is essential for induction of flowering, influenced largely by the duration of photoperiod. To understand the structural and regulatory nature of this gene, a genome-wide survey was carried out, revealing the presence of 13 PEBP (FT) family genes in C. cajan . Based on the gene expression profiling of 13 PEBP genes across the 30 tissues of C. cajan , CcFT6 and CcFT8 were found to be probable Flowering locus T genes responsible for the production of florigen as both of them showed expression in reproductive leaf. Expression analysis in photoperiod sensitive, MAL3 genotype revealed that CcFT6 is upregulated under SD. However, in photoperiod insensitive genotype (ICP20338) CcFT6 and CcFT8 were upregulated in SD and LD, respectively. Hence, in ICP20338 under SD, flowering induction occurs with the involvement of CcFT6 while under LD, flowering induction seems to be associated with the expression of CcFT8. CcFT6 was found to be expressed only under favourable photoperiodic condition (SD) in both MAL3 and ICP20338 and may be regulated through a photoperiod dependent pathway. The presence of additional florigen producing gene, CcFT8 in ICP20338 which has the ability to flower in a photoperiod independent manner under LD conditions might provide some clues on its photoperiod insensitive nature. This study will provide a detailed characterization of the genes involved in photoperiodic regulation of flowering in C. cajan., Competing Interests: Conflict of interestThe authors declares no competing interests., (© King Abdulaziz City for Science and Technology 2020.)