The ABC transporters and their epigenetic regulation under drought stress in chickpea

Chickpea (Cicer arietinum L.) is a globally essential pulse crop, providing dietary protein for millions. However, it suffers significant yield losses due to drought stress, therefore, identification of genes that confer drought tolerance is crucial. The ATP-binding cassette (ABC) transporters are vital proteins in plant growth and development, facilitating the transport of phytohormones like abscisic acid (ABA) that helps plants adapt to drought conditions. In this study, we identified 121 ABC transporter genes in chickpea, categorized into eight subfamilies. Consistent with other crops, the CaABCG family was the largest, with 48 members, while the CaABCE family had only one protein. Structural analysis revealed a conserved domain organization, including Walker A and B motifs and the ABC signature motif. Both segmental and tandem duplications were observed, with the highest duplication in the CaABCG and CaABCC subfamilies. Using RNA-seq and Whole Genome Bisulfite Sequencing (WGBS) data from the root tissues of two chickpea genotypes contrasting in drought tolerance, we found that DNA methylation at cytosine residues might regulate these genes under drought stress. Notably, the CaABCG41 gene was identified as drought-responsive, showing significant upregulation (p < 0.05) and hypermethylation (q < 0.01) in the drought tolerant genotype compared to the drought sensitive genotype under drought stress. CaABCG41 thus holds potential for developing drought-tolerant chickpea cultivars.