Melatonin-induced glycerolipid remodeling enhances photosynthetic performance under cadmium stress in tomato

Soil cadmium (Cd) contamination critically constrains plant production and jeopardizes food safety. Melatonin (MT), a multifunctional signaling molecule, mediates a pivotal role in enhancing plant resilience to abiotic stress. Given the centrality of membrane lipids in stress adaptation, this study utilized glycerolipidomic profiling to delineate MT-induced lipid alterations in tomato plants under Cd stress. Results showed that exogenous MT application significantly increased the contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), phosphatidylcholine (PC) and phosphatidylglycerol (PG) under Cd exposure. Specifically, the abundance of key lipid species including MGDG C36:6, DGDG C36:6, SQDG C34:3, PC C34:3, PE C34:2 and PG C34:3, was higher in MT-treated plants. Consequently, MT application resulted in a higher degree of lipid unsaturation under Cd stress. Furthermore, MT alleviated the Cd-induced decline in the ratios of DGDG/MGDG and PC/PE. These MT-mediated glycerolipid changes contributed to maintaining membrane fluidity and integrity, which ultimately supported the protection of photosynthetic function. Collectively, our finding demonstrate that MT-induced glycerolipid remodeling underpins enhanced photosynthetic performance in tomato under Cd stress.