Genetic and Environmental Regulation of Anthocyanin Biosynthesis in Winged Bean (Psophocarpus tetragonolobus L.)

The winged bean ( Psophocarpus tetragonolobus L.) is a nutrient-rich yet underutilized legume with protein and oil contents comparable to those of soybean. Some genotypes exhibit distinct anthocyanin pigmentation in various plant parts, which helps the plant cope with biotic and abiotic stresses. These anthocyanin pigments have traditionally been used as natural food colorants and are also potential pharmaceutical ingredients, offering various health benefits to humans and animals. This study aimed to identify and quantify major anthocyanins in different tissues of winged bean, analyze their developmental and temperature-dependent accumulation patterns, identify candidate biosynthetic genes, and validate their expression under low-temperature conditions using RT-qPCR. Ultra-Performance Liquid Chromatography (UPLC) analysis revealed the presence of delphinidin-3-glucoside and cyanidin-3-glucoside as the two major anthocyanins in winged bean, with their contents increasing in leaves and pods—particularly in mature leaves and young pods—under declining temperature conditions. Candidate gene mining within QTL-mapped genomic regions identified two putative regulators of anthocyanin biosynthesis: PT04_g20719 ( AP2 ethylene-responsive transcription factor BBM2 ) and PT04_g20862 ( gibberellin 3-beta-dioxygenase 4 ). RT-qPCR analysis confirmed their differential expression, with significantly higher transcript levels in the high-anthocyanin-accumulating genotype WB Purple-3 compared to WB CR-2 in tissues harvested in November - a period characterized by cold climatic conditions. These findings suggest that anthocyanin biosynthesis in winged bean is strongly influenced by temperature and regulated by hormone signaling. This insight provides a valuable foundation for breeding programs aimed at enhancing anthocyanin accumulation in winged bean for increased industrial and nutraceutical value.