Integrated multi-omics and physiological profiling uncover the molecular basis of leaf color transition in an albino mutant of Camellia sinensis cv. Huangshanbaicha 1 during its albinotic stage

Albino tea cultivars have gained considerable attention in the tea industry because of their distinctive flavor profiles, characterized by enhanced freshness and reduced astringency compared with those of conventional green tea cultivars. Nevertheless, the molecular mechanisms underlying dynamic color transitions in tea leaves during different developmental stages remain poorly understood. In this study, we employed a multi-omics approach to investigate leaf color variation by analyzing the same leaf positions from the albino cultivar ‘Huangshanbaicha 1’ (HSBC1) and the green-leaved cultivar ‘Huangshanzhong’ (HSZ) across four developmental stages. Through integrated histological, transcriptomic, proteomic, and metabolomic analyses, we observed that chloroplasts in the albino HSBC1 leaves exhibited developmental anomalies, manifesting as the absence of typical thylakoid vesicles and disorganized lamellar structures. The chlorophyll deficiency observed in albino leaves correlated with impaired chloroplast biogenesis and the downregulation of critical structural genes involved in both photosynthetic pathways and chlorophyll biosynthesis. Furthermore, our findings suggest a coordinated regulation of leaf color plasticity in HSBC1 through plant endogenous hormones and transcription factor networks, including MYB, bZIP, and bHLH families. Proteomic profiling revealed a diminished abundance of photosystem components in HSBC1 compared with that in HSZ, consistent with ultrastructural defects in chloroplast organization. Additionally, although partial recovery of enzymatic activities associated with photosystem II and light-harvesting complexes occurred during leaf re-greening, these levels remained suboptimal relative to those in HSZ, indicating persistent functional impairments. Our results delineate an intricate regulatory network involving core photosynthetic genes, transcriptional regulators, and phytohormonal signals that collectively govern chlorophyll metabolism and chloroplast development in the HSBC1 and HSZ cultivars of the tea plant ( Camellia sinensis ). Together, these findings advance our understanding of the mechanisms underlying albinism in tea plants and provide valuable genetic resources for optimizing tea germplasm through molecular breeding strategies. Albino tea cultivars are widely cultivated because tea processed from albino tea cultivar endows the “umami” taste, and usually exhibits higher freshness and less astringency than green tea cultivar. However, previous studies have scarcely explored the molecular mechanisms responsible for the continuous changes in tea leaf color change at different leaf developmental stages. In this study, the albino cultivar ‘HSBC1’ and green-leaved cultivar ‘HSZ’ with the same leaf position were used as the research objects. Through comprehensively jointed analysis of histological observation, transcriptome, proteomics and metabolites determination, it was found that the main reasons for the reduction of chlorophyll content in the albino leaves were defects in chloroplast development. Further, the DEGs and DEPs integrated analysis demonstrated that repression of transcriptional expression of key structural genes and inhibition of protein levels of core proteins are associated with photosynthesis and chlorophyll synthesis pathways. Additionally, plant endogenous hormones and transcription factors also contributed in regulating leaf color formation in ‘HSBC1’ cultivar. With the return of leaf color to green, the activities of ‘HSBC1’ leaf photosystem and light-trapping protein showed a certain degree of enhancement, yet remained lower than ‘HSZ’. This suggests that the unique expression patterns of genes (proteins) at varying temperatures and cultivars may contribute to the leaf color change in tea plant. These data demonstrated the existence of a regulatory network between key genes, important transcription factors, and endogenous hormones during photosynthesis and chlorophyll biosynthesis in tea plant. These results contribute to gaining a deeper and broader understanding of molecular mechanism of leaf whitening in tea plant, and pave a theoretical basis as well as excellent genetic resources in tea industry. • Repression of the biosynthesis of chlorophyll causes leaf albinism of ‘HSBC1’. • Abnormal chloroplast structure of ‘HSBC1’ was due to destruction of photosynthesis-antenna proteins and photosynthesis. • The interaction network of key genes, endogenous hormones, and transcription factors coordinated leaf albinism of ‘HSBC1’ together.