Exocyst subunit EXO70J7 mediates cold-induced plasma membrane-associated vesicular trafficking and regulates cold tolerance in rice.

Cold stress severely impairs crop growth, development and yield. Exploring the regulatory genes underlying cold tolerance in crops and elucidating their molecular mechanisms is critical for cold tolerance breeding. In this study, quantitative real-time PCR (qRT-PCR) revealed that the expression of EXO70J7, which encodes an exocyst complex subunit localized to vesicles and the plasma membrane (PM), was induced by cold stress. EXO70J7 loss-of-function mutants generated using CRISPR-Cas9 exhibited reduced cold tolerance. Transcriptomic analysis revealed altered expression of cold-response pathway genes in EXO70J7 loss-of-function mutants under cold stress. Conversely, transgenic plants overexpressing EXO70J7 displayed enhanced cold tolerance. Transmission electron microscopy revealed that loss of EXO70J7 function exacerbated, whereas overexpression alleviated, cold-induced plasma membrane damage compared with wild-type plants (WT). Subcellular localization analysis of EXO70J7-GFP in root tip cells revealed cold-induced accumulation at the PM, which was inhibited by vesicle trafficking inhibitor, brefeldin A (BFA), treatment and restored upon BFA washout. Based on these results, we propose that EXO70J7 influences PM integrity by mediating PM-associated vesicle trafficking under cold stress, thereby contributing to cold tolerance in rice. In addition, haplotype and population genetic analyses revealed pronounced genetic divergence at EXO70J7 between indica and japonica subspecies, consistent with signatures of divergent selection driven by thermal adaptation, highlighting its great potential as a target for cold-tolerance rice breeding.