Apple gene MdXTH15, encoding endotransferase/hydrolase for xyloglucan, can improve plant resistance to drought, salt, and pathogen stresses

The outermost protective layer of plant cells is known as the cell wall, and it mostly comprises cellulose, hemicellulose, and pectin. The primary component of the hemicellulose in the cell wall of higher plants is xyloglucan, which provides the cell wall with mechanical support and restricts cell growth. XTH gene family members contribute to the remodeling of plant cell walls by encoding proteins with glycosyltransferase/hydrolase activity, which can mediate the cleavage and rearrangement of xyloglucan chains. Plants can enhance their resilience to external stress by modifying the structure and composition of the cell wall. However, few studies have been conducted on the XTH gene family in apples. Here, we successfully isolated MdXTH15 from the apple genome and found that it contained a highly conserved GH16-XET domain. The expression of this gene was highest in the stem of the apple, and it responded to external abiotic stress treatment. The protein was found to be localized to the plasma membrane by subcellular localization analysis. Its overexpression enhanced abiotic stress and pathogen resistance in both apple and Arabidopsis. Furthermore, we elucidated the molecular mechanisms underlying stress resistance at the cell wall level and provided a novel perspective on this phenomenon. Overall, our findings provide a novel approach for enhancing the stress resistance of apples.