Genome-wide bisulphite-sequencing reveals organ-specific methylation patterns in chickpea

DNA methylation is widely known to regulate gene expression in eukaryotes. Here, we unraveled DNA methylation patterns in cultivated chickpea to understand the regulation of gene expression in different organs. We analyzed the methylation pattern in leaf tissue of wild chickpea too, and compared it with cultivated chickpea. Our analysis indicated abundant CG methylation within gene-body and CHH methylation in intergenic regions of the chickpea genome in all the organs examined. Analysis of differentially methylated regions (DMRs) demonstrated a higher number of CG context DMRs in wild chickpea and CHH context DMRs in cultivated chickpea. We observed increased preponderance of hypermethylated DMRs in the promoter regions and hypomethylated DMRs in the genic regions in cultivated chickpea. Genomic location and context of the DMRs correlated well with expression of proximal genes. Our results put forth a positive correlation of promoter hypermethylation with increased transcript abundance via identification of DMR-associated genes involved in flower development in cultivated chickpea. The atypical correlation observed between promoter hypermethylation and increased transcript abundance might be dependent on 24-nt small RNAs and transcription factors binding to the promoter region. This study provides novel insights into DNA methylation patterns in chickpea and their role in regulation of gene expression.