Metabolic and RNA sequencing analysis of cauliflower curds with different types of pigmentation

It is a worldwide problem that cauliflower curds turn purplish at low temperatures, which seriously affects the quality of the product. The molecular mechanism is not clear so far. This study will reveal the causes of purplish curds under low temperature stress for the first time at the genetic level, provide conclusive molecular evidence for the accurate creation and improvement of cauliflower resources and provide a new theoretical approach for solving the problem that curds turn purple under low temperature stress in cauliflower. Cauliflower (Brassica oleracea var. botrytis) is a popular vegetable worldwide due to its delicious taste, high nutritional value and anti-cancer properties. Cauliflower normally produces white curds, and natural spontaneous mutations lead to the production of orange, purple or green curds. However, some white cauliflowers show uneven purple pigmentation in their curds, which seriously affects the appearance quality and economic value of this crop. The underlying mechanism is still unclear. In this study, we performed comparative transcriptional and metabolic profiling analysis of light orange, white and purplish cauliflower curds. Metabolite analysis revealed that the pigments conferring purple colouration were delphinin and cyanin. Transcriptome analysis showed that the anthocyanin metabolism-related structural genes DFR, ANS and UGT and the transcription factor genes PAP2, TT8, GL3, EGL3 and TTG1 were upregulated in purplish versus white curds. These findings shed light on the formation of purplish curds, which could facilitate the breeding of purely white or red cauliflower.