A hickory diacylglycerol acyltransferase gene coordinates fatty acid metabolism and aluminum tolerance in plants

Triacylglycerol (TAG) accumulation and abiotic stress tolerance are critical for woody oil crop productivity, yet their coordination remains poorly understood. Here, we characterized CcDGAT1, a diacylglycerol acyltransferase 1 gene from hickory (Carya cathayensis) that links oil accumulation with aluminum (Al) tolerance. CcDGAT1 was highly expressed in developing kernels and vegetative tissues and was strongly induced by Al stress. CcDGAT1 overexpression increased total oil content and unsaturated fatty acid levels and enhanced Al tolerance, as shown by improved membrane integrity, root growth, and biomass. Under Al stress, CcDGAT1 overexpression promoted the accumulation of 18:2/18:3-containing TAGs while reducing 18:2/18:3-enriched membrane lipid pools. Consistent with this protective role, transient silencing of CcDGAT1 in hickory roots aggravated Al-induced lipid peroxidation and electrolyte leakage. Dual-luciferase, yeast one-hybrid, and electrophoretic mobility shift assays demonstrated that CcATML1 and CcWRKY11a directly activate CcDGAT1 transcription. Overexpression of these transcription factors increased CcDGAT1 expression, fatty acid content, membrane integrity, and Al tolerance. Together, these findings establish CcDGAT1 as a functional oil-promoting DGAT1 in hickory and support a model in which CcDGAT1-associated lipid remodeling contributes to Al-stress protection. The CcATML1/CcWRKY11a-CcDGAT1 module further provides a transcriptional framework for linking lipid metabolism with stress resilience in woody oil crops.