Sun_2025_Plants.(Basel)_15_35

Phospholipid:Diacylglycerol Acyltransferase (PDAT) catalyzes the final step of the acyl-CoA-independent triacylglycerol (TAG) biosynthesis pathway and plays an important role in lipid metabolism and abiotic stress responses in plants. Oat (Avena sativa L.) possesses the highest lipid content among cereal crops, yet the functions of PDAT genes in this species remain largely unexplored. In this study, we identified and characterized three AsPDAT genes in oat, which form a homeologous triplet evenly distributed across the three subgenomes and show high conservation in sequence and gene structure. Phylogenetic analysis indicated a clear divergence between monocot and dicot PDATs. Expression profiling revealed that the three AsPDAT genes share similar organ-specific and stress-responsive expression patterns, suggesting functional conservation following polyploidization, with AsPDAT-5C showing relatively higher transcript levels. The enzymatic activity of AsPDAT-5C was confirmed by complementation of the TAG-deficient yeast quadruple mutant H1246. Transient expression in Nicotiana benthamiana epidermal cells demonstrated that AsPDAT-5C localizes to the endoplasmic reticulum. Stable overexpression of AsPDAT-5C in Nicotiana tabacum significantly increased lipid content in both leaves and seeds without compromising plant growth and enhanced tolerance to cold and phosphorus-deficiency stresses. Our results provide new insights into the AsPDAT gene family and underscore the potential of AsPDAT-5C in engineering lipid biosynthesis and improving stress resilience in plants.