Identification of GSTs and MATE transporters associated with proanthocyanidin accumulation in <i>Cerasus humilis</i>

Cerasus humilis (Bge.) Sok. fruits have high proanthocyanidin (PA) content. We aimed to identify and perform preliminary functional evaluations of four candidate transport-related genes to investigate their roles in PA accumulation. We analyzed the gene expression patterns, determined the subcellular localization of associated proteins, conducted phylogenetic analyses to examine their evolutionary orthologs, evaluated their roles in PA accumulation through overexpression assays, and performed molecular docking simulations to analyze binding between these candidate transporters and the specific PA monomers catechin and epicatechin. Together, ChGST2 , ChMATE1 , and ChMATE2 expression levels were correlated with PA accumulation; ChGST1 and ChGST2 were localized in the cytoplasm and nucleus; ChMATE1 and ChMATE2 were localized in the vacuolar membrane (tonoplast). Phylogenetic analyses confirmed that ChGST1/2 and ChMATE1/2 are true orthologs of well-characterized plant PA transporters. Furthermore, overexpression of ChGST2 , ChMATE1 , and ChMATE2 enhanced PA accumulation, indicating ChGST2 and ChMATE1/2 play roles in the PA accumulation pathway in C. humilis . Our findings implied GSTs and MATE genes might be important for the nutritional value of berries via enhancing the PA accumulation.