LhCAT2-mediated crosstalk between reactive oxygen species homeostasis and anthocyanin biosynthesis enhances zinc tolerance in Liriodendron hybrid.

Excessive zinc (Zn) accumulation in soils impairs plant growth and threatens ecosystem sustainability. Although catalase (CAT) enzymes are central to antioxidant defense, their coordination with secondary metabolism in woody plants under heavy metal stress remains poorly understood. Here, we characterized LhCAT2, a Zn-inducible catalase gene from Liriodendron hybrid, using three Arabidopsis overexpression lines and two Liriodendron hybrid overexpression lines under controlled Zn treatments. Under Zn stress, LhCAT2 overexpression increased Arabidopsis germination rate by 22%, primary root length by 19%, lateral root number by 3.3-fold, fresh weight by 56%, and chlorophyll content by 30%. In Liriodendron hybrid, fresh weight and chlorophyll content increased by 67% and 48%, respectively. Across both species, shoot Zn content decreased by 32-36%, whereas root Zn content increased by 27-107%, consistent with enhanced root retention and restricted root-to-shoot translocation. LhCAT2 overexpression also reduced reactive oxygen species and malondialdehyde levels, increased superoxide dismutase and catalase activities, enhanced anthocyanin accumulation, and upregulated anthocyanin biosynthetic genes. These findings suggest that LhCAT2 coordinates enzymatic ROS scavenging with anthocyanin-related antioxidant responses, thereby mitigating oxidative damage and sustaining growth under Zn stress. LhCAT2 therefore represents a candidate gene for improving Zn tolerance in woody plants.