Genomic, structural, and molecular analysis of calmodulin-binding transcriptional activators (CAMTAs) suggests their role in plant development and abiotic stress tolerance in chickpea

The calmodulin-binding transcriptional activator (CAMTA) transcription factors regulate the expression of target genes in Ca^{2 +} dependent cellular functions. CAMTAs are known to regulate biotic and abiotic stress tolerance, and development in plants. CAMTA family has been characterized in Arabidopsis, it is yet to be explored in the legume plant chickpea. Here, we have identified and characterized the chickpea CAMTA family. Total seven <i>CAMTA</i> genes (<i>CaCAMTA1-7</i>) were identified in chickpea. Gene and domain structure analyses suggested that CAMTAs are structurally conserved. The phylogenetic analysis demarcated CaCAMTAs into three groups namely; group I, II and III, and indicated that CaCAMTAs have co-evolved in dicot leguminous plants whereas, they have divergent evolution in monocots. Protein homology modeling revealed their three-dimensional structure, and composition & conformations of α-helix, β-sheets and p-loops. Subcellular localization showed that CaCAMTA4 was localized both, in the nucleus and the cytosol whereas, CaCAMTA5 was localized in the nucleus. CaCAMTA promoters contain various <i>cis</i>-regulatory elements related to abiotic stresses and plant development. Expression profiling using RNA-seq data revealed differential expression of CaCAMTAs during various stages of plant development. RT-qPCR expression analysis showed that most <i>CaCAMTA</i> genes are drought, salt, and ABA responsive, suggesting their role in abiotic stress tolerance in chickpea. Moreover, CaCAMTA regulon was identified based on the presence of CAMTA binding motif (CGCG box) in the promoters of target genes, and <i>in-silico</i> interaction analysis of TF and putative targets. Overall, CaCAMTAs are crucial for abiotic stress tolerance and plant development in chickpea. Key <i>CaCAMTA</i> genes will be functionally characterized, and will be exploited for developing stress tolerant chickpea varieties.