CbLTP67 Negatively Regulates Salt Tolerance by Interaction With CbPAT12 and CbRD19A to Disrupt Salicylic Acid-Mediated Stomatal Closure in Catalpa bungei.

Salt stress severely constrains growth and wood quality in woody plants. Although non-specific lipid transfer proteins (nsLTPs) are known to participate in stress responses, their function in the valuable timber species Catalpa bungei remains largely unexplored. Here, we characterized CbLTP67, a guard cell-enriched gene whose expression is downregulated by both salt stress and salicylic acid (SA). Overexpression of CbLTP67 resulted in excessive accumulation of reactive oxygen species (ROS), weakened antioxidant capacity, and reduced survival under salt stress. Specifically, CbLTP67 overexpression impaired stomatal closure following salt treatment, whereas exogenous SA application restored normal stomatal aperture and mitigated salt-induced damage. Time-resolved transcriptomic analysis showed that differentially expressed genes (DEGs) were significantly enriched in pathways related to SA signaling and stomatal movement. Moreover, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays identified CbRD19A and CbPAT12 as specific interacting partners of CbLTP67 at the plasma membrane. Both proteins were induced by salt stress. Interestingly, CbLTP67 contains three predicted palmitoylation sites that are absent in CbRD19A. Together, our findings support a novel CbPAT12-CbLTP67-CbRD19A regulatory module that negatively modulates salt tolerance by disrupting SA-mediated stomatal closure in C. bungei.