Integrated metabolomics and proteomics analyses reveal the molecular mechanism underlying the yellow leaf phenotype of Camellia sinensis

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.