Genetic and environmental regulation of anthocyanin biosynthesis in winged bean (Psophocarpus tetragonolobus L.)

Winged bean (Psophocarpus tetragonolobus L.) is a nutrient-dense yet underutilized legume, with protein and oil contents comparable to those of soybean. Certain genotypes exhibit distinct anthocyanin pigmentation across various plant organs, contributing to resilience against biotic and abiotic stresses. Traditionally, these anthocyanin pigments have served as natural food colorants and are recognized as potential pharmaceutical ingredients, providing diverse health benefits to humans and animals. The present study identified and quantified major anthocyanins in different winged bean tissues and examined their accumulation patterns in relation to developmental stage and temperature. Additionally, candidate biosynthetic genes were identified, and their expression patterns under low-temperature conditions were analyzed using RT-qPCR to evaluate their potential roles in anthocyanin biosynthesis. Ultra-Performance Liquid Chromatography (UPLC) analysis detected delphinidin-3-glucoside and cyanidin-3-glucoside as the predominant anthocyanins in winged bean. The concentrations of these compounds increased in leaves and pods, particularly in mature leaves and young pods, as temperatures declined. Candidate gene mining within QTL-mapped genomic regions identified two putative regulators of anthocyanin biosynthesis: PT04_g20719, an AP2 ethylene-responsive transcription factor (BBM2), and PT04_g20862, a gibberellin 3-beta-dioxygenase 4. RT-qPCR analysis confirmed differential expression of these genes, with significantly higher transcript levels observed in the high-anthocyanin-accumulating genotype WB Purple-3 compared to WB CR-2 in tissues collected during November, a period characterized by low temperatures. The results suggest that anthocyanin biosynthesis in winged bean is influenced by temperature and developmental factors. This discovery establishes a foundation for breeding programs focused on increasing anthocyanin accumulation in winged bean to enhance its industrial and nutraceutical value.