Molecular mechanism of light-responsive transcription factor ELONGATED HYPOCOTYL 5 regulating anthocyanin synthesis...

This study used molecular biology and biochemical methods to elucidate the core regulatory role of the light responsive transcription factor CsHY5 in anthocyanin synthesis in tea plants (Camellia sinensis). CsHY5 cloned from the high anthocyanin variety 'Botang Ziya' possesses bZIP domain, nuclear localization, and lacks transcriptional activation activity. The shading treatment inhibited anthocyanin accumulation and downregulated the expression of CsHY5 and key biosynthetic genes, including CsDFR and CsANS. Overexpression of CsHY5 in tobacco promotes anthocyanin synthesis, while gene silencing has the opposite effect. Mechanistic studies have shown that CsHY5 directly activates transcription by specifically binding to G-box elements in the promoter region of structural genes, and synergistically enhances this activation effect by forming heterodimers with CsbHLH79. At the same time, CsHY5 interacts with the MBW complex (CsMYB114-CsbHLH79-CsTTG1) to form the "HY5-MBW" regulatory module, and constructs a hierarchical pathway by directly activating CsbHLH89 expression. These findings indicate that CsHY5 is a central light responsive transcription factor that coordinates the biosynthesis of tea anthocyanin through direct gene activation, protein interactions, and the formation of key regulatory complexes.