Tea plant (Camellia sinensis (L.) O. Kuntze) is a cold-sensitive leaf-harvesting crop whose growth, yield, and processed tea quality are all inhibited by low temperatures. Therefore, identifying the regulatory genes involved in tea plant growth and freezing tolerance is crucial for genetic improvement. WRKY transcription factors regulate various plant processes, including growth and development, stress responses, and metabolite biosynthesis. However, the molecular network through which WRKY coordinates these pathways in tea plants remains unclear. In this study, we revealed that CsWRKY57L, a cold-inducible WRKY IIc subfamily member, positively regulated freezing tolerance by directly promoting flavonoid accumulation in tea plants. Transient suppression of CsWRKY57L weakened the freezing tolerance of tea plants by reducing flavonoid content and suppressing the C-repeat-binding factor (CBF) - cold-responsive (COR) gene pathway. In contrast, heterologous overexpression of CsWRKY57L in Arabidopsis had the opposite effect. Additionally, overexpression of CsWRKY57L inhibited reproductive development and accelerated senescence in Arabidopsis. Interaction analysis revealed that CsWRKY57L directly binds to the promoters of CsSWEET1a, CsSWEET15, and AtSWEET15, which encode sugar transporters essential for plant reproductive development, and inhibits their transcription. Overall, the study revealed a dual role of CsWRKY57L in promoting freezing tolerance via flavonoid biosynthesis and inhibiting reproductive development by regulating SWEETs expression. This study uncovers a novel mechanism whereby CsWRKY57L coordinately regulates both stress responses and growth in tea plants, providing a molecular basis for breeding low-temperature-tolerant varieties with restricted reproductive development.

The tea plant cultivar ‘Zhonghuang 2’ (ZH2) possesses albino-induced yellow leaves that contain low levels of catechins but high contents of amino acids. However, the molecular mechanism underlying the yellow leaf phenotype of ZH2 has not been elucidated clearly. In the current research, the yellow shoots (ZH2-Y) and naturally converted green shoots (ZH2-G) of ZH2 were studied using metabolic and proteomic profiling for a better understanding of the mechanism underlying phenotype formation. In total, 107 differentially changed metabolites (DCMs) were identified from the GC‒MS-based metabolomics, and 189 differentially accumulated proteins (DAPs) were identified from the tandem mass tag (TMT)-based quantitative proteomics. Subsequently, integrated analysis revealed that ‘porphyrin and chlorophyll metabolism’, ‘carbon fixation in photosynthetic organisms’, and ‘phenylpropanoid biosynthesis’ pathways were commonly enriched for DAPs and DCMs. We further found that the inhibition of chlorophyll biosynthesis, the deficiency of photosynthetic proteins and the imbalance of the ROS-scavenging system were the crucial reasons responsible for the chlorosis, chloroplast abnormality and photooxidative damage of ZH2 leaves. Altogether, our research combines metabolomics and proteomics approaches to uncover the molecular mechanism leading to the yellow leaf phenotype of tea plants.