Role of Chloroplast Lipid-Remodelling Protein 23 During Cold Acclimation in Arabidopsis thaliana

Cold acclimation is a crucial physiological process that enables plants to adapt to low temperatures. A key aspect of this adaptation is lipid remodelling, which preserves membrane fluidity and integrity under cold stress. Proteins of the chloroplast envelope membranes are increasingly recognized for their role in acclimation to changing environmental conditions. While lipid synthesis occurs at the inner envelope membrane—where monogalactosyldiacylglycerol synthase is one of the few inner envelope proteins known to face the intermembrane space—little is known about specific proteins involved in lipid remodelling during cold acclimation. In this study, we investigate the role of Chloroplast Lipid Remodelling Protein 23 (CLRP23) as a component of the inner chloroplast envelope membrane. Subcellular fractionation combined with protease protection assays provided evidence for its orientation toward the intermembrane space. To explore its function, we analysed the physiological performance and lipid composition in CLRP23-deficient mutant plants. Under cold stress, we observed significant impairments in photosynthesis and exaggerations in galactolipid response, suggesting CLRP23 is involved in lipid remodelling. Docking analysis suggests CLRP23 may bind to galactolipids, thereby modulating their composition and saturation status. Complemented by transcriptomic and proteomic analyses, these findings expand our understanding of protein-mediated processes during cold acclimation.