Light-induced CsCV triggers chloroplast degradation by destabilizing photosystem proteins in tea plant

Excess light induces chloroplast degradation in plants, leading to decreased photosynthetic efficiency and an albino leaf phenotype. However, the molecular mechanism underlying this process remains unclear, especially in perennial crops like tea plant. This study investigated the effects of relatively strong light (SL, 240 μmol m⁻²·s⁻¹) on chloroplast ultrastructure and metabolites in the light-sensitive tea germplasm Nanchuan Dachashu (Camellia nanchuanica). Continuous exposure to SL resulted in abnormal chloroplast structure characterized by extensive vacuolation. SL also significantly decreased the levels of chlorophyll (−60.30 %), carotenoids (−88.29 %), free amino acids (−23.97 %), and caffeine (−41.15 %) compared to relatively weak light (WL, 15 μmol m⁻²·s⁻¹). Transcriptome analysis and RT-qPCR revealed that the chloroplast vesiculation gene CsCV was significantly up-regulated under SL, with promoter analysis showing more light-responsive elements in CsCV compared to another light-responsive gene, CsNBR1. Overexpression of CsCV in Arabidopsis caused stunted growth and accelerated leaf senescence, with the most affected line showing decreases in chlorophyll and carotenoid contents of 24.97 % and 17.39 %, respectively. Conversely, silencing CsCV in tea plants using antisense oligodeoxynucleotides (asODNs) for 3 days increased chlorophyll and carotenoid levels by 15.98 % and 18.35 %, respectively. Bimolecular fluorescence complementation (BiFC) assays and in protein-protein docking simulations demonstrated that CsCV interacts with the photosystem proteins CsLhca1, CsLhcb4, and CsPsaL through its conserved C-terminal region, suggesting CsCV may trigger chloroplast degradation by destabilizing the photosynthetic apparatus under SL. These findings provide mechanistic insights into light-induced chloroplast degradation in tea plants and highlight CsCV as a potential target for improving crop stress tolerance.