Biochemical analysis of anthocyanin and proanthocyanidin and their regulation in determining chickpea flower and seed coat colour

We define the molecular link between flower and seed colour in chickpea and identify CaMATE1 and CabHLH as the regulators of both traits. Flower and seed coat colour are important agronomic traits in chickpea (Cicer arietinum L.). Cultivated chickpeas are of two types namely, desi (dark seeded, purple flowered) and kabuli (light seeded, white flowered). There has been limited information about the molecular mechanism underlying colour variation of flower and seed coats in desi and kabuli chickpea. We profiled the anthocyanin and proanthocyanidin (PA) contents in chickpea flowers and seed coats. Tissue-specific silencing of two genes encoding a basic helix-loop-helix (CabHLH) protein and a tonoplast-localized multidrug and toxic compound extrusion (CaMATE1) transporter in a desi genotype resulted in the reduction in expression of anthocyanin and PA biosynthetic genes and anthocyanin and PA contents in the flower and seed coat, and produced flowers and seeds with kabuli characteristics. Transcriptional regulation of a subset of anthocyanin and PA biosynthetic genes by a natural CabHLH variant and transport assay of a natural CaMATE1 variant explained the association of these alleles with the kabuli phenotype. We carried out a detailed molecular characterization of these genes, and provided evidence that kabuli chickpea flower and seed colour phenotypes can be derived by manipulation of single genes in a desi chickpea background.

Automated summary

In this study, we identified the key genes CaMATE1 and CabHLH that regulate flower and seed coat colour in chickpea. Silencing these genes resulted in reduced expression and content of anthocyanin and proanthocyanidin (PA) biosynthetic genes, producing flowers and seeds with characteristics similar to kabuli chickpeas.