Molecular regulation mechanisms of Cymbidium sinense leaf variegation

Dr. Jie Gao, a recent Ph. D. graduate, is an associate professor at the Environmental Horticulture Research Institute, Guangdong Academy of Agricultural Sciences, China. The objective of her study focused on the molecular regulation mechanisms of Chinese orchid, Cymbidium sinense, leaf variegation. The Chinese orchid is a symbol of elegance and purity in China. Among Chinese orchids, the leaf color variation of C. sinense is the most abundant. The leaf color variation makes C. sinense more diversified and more valuable. However, the variegation formation process remains largely unexplored. In the present study, the proteome and phosphoproteome of C. sinense leaf variegation mutants were studied using tandem mass tag and liquid chromatography tandem mass spectrometry (TMT and LC-MS/MS) analysis. We identified 1,059 differentially expressed proteins (DEPs) and 1,127 differentially expressed phosphorylation sites belonging to 644 phosphoproteins (DEPPs) in the yellow section of the leaf variegation compared to the green section. Moreover, 349 co-expressing proteins were found in both omic profiles, though only 26 proteins showed the same expression patterns. The interaction network analysis of kinases and phosphatases showed that DEPs and DEPPs in photosynthesis, response to hormone, pigment metabolic process, phosphorylation, glucose metabolic process, and dephosphorylation may contribute to leaf color. Variations in the heat shock protein (HSP) family genes at the protein and phosphorylation levels may significantly affect the leaf variegation. To verify the function of the gene CsHSP70 and its phosphorylation sites, a transiently expressed method was examined in tobacco. These results showed that the mutation of 339T and 603T sites caused a significant decrease in chlorophyll and carotenoid contents in tobacco leaves. This indicated that the 399T phosphorylation site of CsHSP70 protein plays an important role in maintaining chlorophyll content in leaves. Collectively, our current findings constructed a comprehensive view of protein and protein phosphorylation in the regulation of C. sinense leaf variegation, providing valuable insights into the underlying formation process.

Jie Gao won the ISHS Young Minds Award for the best oral presentation at the IV International Orchid Symposium in China in December 2022.

Jie Gao, Environmental Horticulture Research Institute, Guangdong Academy of Agricultural Sciences, No.1, Jinyingdong 1st Street, Tianhe, Guangzhou, China, e-mail: gaojie@gdaas.cn

The article is available in Chronica Horticulturae