Role of miRNAs in the regulation of proanthocyanidin biosynthesis in the legume Psophocarpus tetragonolobus (L.) DC.

Underutilised legume Psophocarpus tetragonolobus (L.) DC. accumulates various degrees of proanthocyanidin (PA) or condensed tannin (CT) on its seed coat. Screening for PA content among various lines of P . tetragonolobus through the vanillin-HCl assay identified two contrasting lines of P . tetragonolobus (HPW and LPW). HPW contained 59.23 mg/g of total PA, with catechin and epigallocatechin gallate monomer being found among the monomers identified in HPLC; the LPW line contained 8.68 mg/g of PA in its leaves. Comparative miRNA profiling of the leaf tissues of contrasting PA lines of P . tetragonolobus revealed a total of 139 mature miRNAs along with the identification of isoforms and novel miRNAs. Differentially expressed known miRNAs, e.g., miR156, miR396, miR4414b, miR4416c, miR894, miR2111, and miR5139, were validated through qRT-PCR. Target prediction of the identified miRNAs show possible involvement of certain miRNAs like miR396, miR4414b and miR862 in PA biosynthesis in P . tetragonolobus . Hence this study can provide a basis for understanding the role of miRNAs in regulation of PA biosynthesis.