PalMYB1R1-PalGRXC11 modulates drought tolerance in Populus alba var. pyramidalis by regulating catalase activity

Drought stress triggers an over-accumulation of reactive oxygen species (ROS), severely impairing physiological growth, long-term wood formation, and bioenergy yield in woody plants. Although CC-type glutaredoxins ( GRXCs ) are known to be involved in plant stress responses, their precise regulatory mechanisms remain largely undefined. This study functionally characterized PalGRXC11 , a CC-type GRX in Populus alba var. pyramidalis , as a negative modulator of drought adaptation. Notably, under normal conditions, palgrxc11 knockout (KO) mutants were phenotypically indistinguishable from wild-type (WT) and overexpression (OE) lines. However, under drought stress, the KO plants exhibited significantly enhanced drought tolerance and efficient ROS scavenging, and these plants maintained higher relative water content (RWC), net photosynthetic rate ( P n), and stomatal conductance ( g sw ), achieving a remarkable 72.22% survival rate upon rewatering. Furthermore, we identified that PalMYB1R1 was significantly upregulated by drought, and its overexpression enhanced drought tolerance in poplar. As an upstream transcriptional repressor, PalMYB1R1 specifically targets and physically interacts with the PalGRXC11 promoter to reduce its expression. We also demonstrated that PalGRXC11 physically interacts with the catalase PalCAT3 and inhibits its enzymatic activity, thereby impairing H 2 O 2 clearance and leading to oxidative damage. Collectively, our results elucidate a novel PalMYB1R1-PalGRXC11-PalCAT3 regulatory cascade that maintains redox homeostasis under drought stress, offering a potential genetic target to uncouple drought tolerance from growth penalties in the breeding of drought-resilient bioenergy poplars.