CsHB5-CsWRKY22 coordinates chlorophyll degradation and reactive oxygen species homeostasis to control leaf senescence...

Premature leaf senescence compromises leaf tenderness, reduces tea yield, and hinders the sustainable development of the tea industry. However, the molecular mechanisms regulating leaf senescence in tea plants remain largely unresolved. Here, we identify CsHB5 (Homeobox5) and CsWRKY22 (WRKY transcription factor 22) as positive regulators of leaf senescence in Camellia sinensis. Both genes exhibit markedly increased transcript levels during aging. Virus-induced gene silencing of either CsHB5 or CsWRKY22 delayed leaf senescence by suppressing chlorophyll degradation and limiting reactive oxygen species (ROS) accumulation, whereas their overexpression accelerated senescence in tea and Arabidopsis thaliana. We further show that CsHB5 physically interacts with CsWRKY22, and together they synergistically activate CsNYE1 transcription through direct promoter binding. This cooperative activation enhances chlorophyll breakdown and ROS production, thereby promoting senescence progression. Our findings reveal a previously uncharacterized CsHB5-CsWRKY22-CsNYE1 (Non-Yellowing1) regulatory module that integrates chlorophyll catabolism and ROS homeostasis to control leaf senescence in tea plants. This work provides a mechanistic framework for delaying senescence and extending the tender phase of tea leaves.