CsZAT12 interacts with CsNAC87 to repress chlorophyll accumulation in albino leaves of tea plants

The albino leaves of cold-sensitive tea plants exhibited a marked reduction in chlorophyll content. However, the underlying regulatory mechanism remains elusive. In this study, we determined lower chlorophyll levels in tender leaves of cold-sensitive 'Baiye 1' compared to green leaves during the spring. Comparative transcriptome analyses identified the chlorophyll biosynthesis gene CsPORA, which was significantly downregulated in albino leaves. Functional assays confirmed that CsPORA positively regulates chlorophyll content. Electrophoretic mobility shift assay, yeast one-hybrid, dual-luciferase, and GUS staining results demonstrated that CsNAC87 binds to the promoter of CsPORA and suppresses its expression. Additionally, CsZAT12 physically interacts with CsNAC87 to enhance the repression. Overexpression of either CsZAT12 or CsNAC87 negatively regulated chlorophyll accumulation in tea plants and tobacco leaves, while co-transformation of CsZAT12 and CsNAC87 intensified the albino phenotype in tobacco leaves. Low temperature treatment of 'Baiye 1' triggered the marked upregulation of CsNAC87 and CsZAT12, leading to dramatical downregulation of CsPORA and leaf albinism. Collectively, our study reveals a novel cold-responsive CsZAT12-CsNAC87 module that negatively regulates chlorophyll synthesis by repressing CsPORA, providing new insights into chlorophyll metabolism in albino leaves of cold-sensitive tea cultivars.