ER-localized GDSL lipase ZmSWL3 regulates drought resistance in maize

GDSL lipases play important roles in plant growth, development, and stress responses; however, the molecular mechanisms underlying drought tolerance remain unclear. Here, we characterized two allelic maize mutants, swl3-1 and swl3-2, displaying leaf rolling and reduced plant height under drought conditions. The drought-sensitive phenotypes observed in swl3-1 and swl3-2 arise from an underlying defect in xylem vessel development. Map-based cloning revealed that ZmSWL3 encodes an endoplasmic reticulum (ER)-localized GDSL lipase. ZmSWL3 expression is predominant in roots and internodes and indicates a primary water transport function. Biochemical assays confirmed that both the G396 residue (the mutation site in swl3-1) and catalytic residue S107 are essential for the lipase activity of ZmSWL3. Furthermore, ZmSWL3 loss of function altered the internal lipid composition, notably reducing linolenic acid (C18:3) levels, which is strongly associated with drought. Our findings elucidate a novel mechanism by which GDSL lipase modulates vascular development and lipid metabolism to confer drought tolerance, thus providing a promising genetic resource for maize breeding.