Integrated metabolome and transcriptome reveals the mechanism of the flower coloration in cashew (Anacardium occidentale Linn.)

Abstract

Background Cashew is a widely attractive food in the world with high nutritional value for human health. The quality of cashew is closely associated with the flower coloration. However, the underlying mechanism of flower coloration of cashew was poorly understood. Here, we identified two cashew cultivars with variable flower coloration. Then, integrated analysis of metabolome and transcriptome was performed to explore the potential mechanisms. Results The results showed that 8 flavonoid compounds were markedly accumulated in red flower cashew, including taxifolin, procyanidin B2, delphinidin-3-O-glucoside, peonidin-3-glucoside, L-epicatechin, chalconaringenin, luteolin, naringenin and chrysin. In particular, delphinidin-3-O-glucoside, peonidin-3-glucoside and procyanidin B2 were key metabolites that promoted the formation of red flower coloration. Transcriptome analysis revealed that genes involved in flavonoid biosynthesis were also varied among these two cultivars. The flavonoid biosynthesis direction was reprogrammed to synthesize delphinidin-3-O-glucoside, peonidin-3-glucoside and procyanidin B2. Typically, four core genes encoding anthocyanin synthesis were also highly expressed in cashew with red flower, including CFI (TRINITY_DN4346_c0_g1), CHS2 (TRINITY_DN16129_c0_g1), CHS1 (TRINITY_DN2623_c0_g1) and F3H (TRINITY_DN8780_c0_g1). Conclusions This study sheds light on flavonoid metabolic pathways and candidate genes varied in two cashew cultivars and lays a foundation for the breeding programs of cashew.