Leaf-color variation in plants should be associated with chlorophyll metabolism and chloroplast development. Here, we characterized a low-temperature-sensitive pakchoi DH line, 1197, which exhibited green leaves at 25 °C, but showed yellowing at 4 °C. Low temperature significantly reduced chlorophyll accumulation and disrupted chloroplast ultrastructure. After transfer from 4 °C to 25 °C for 7 days, yellow leaves partially regreened, and chlorophyll a content increased by 366.67%. RNA-seq analysis identified 3058 core DEGs associated with the yellowing–regreening transition, which were significantly enriched in photosynthesis–antenna proteins, photosynthesis, and porphyrin metabolism pathways. Leaf yellowing was characterized by repression of chlorophyll biosynthesis genes (e.g., CHLD, CHLM, PORC) and induction of degradation genes (SGR1, SGR2, NYC1, PAO), together with widespread downregulation of chloroplast function-related genes. In addition, GLK2, HBI1, NAC047, and NAC029 were identified as candidate regulators of temperature-dependent leaf-color conversion. This study provides candidate molecular insights into low-temperature-induced yellowing and regreening in pakchoi and offers candidate genes for future functional validation and Brassica breeding.
Tu et al. (Fri,) studied this question.