Characterization of PDAT Genes in Oat (Avena sativa L.) and the Role of AsPDAT-5C in Lipid Biosynthesis and Abiotic Stress Response

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 (<i>Avena sativa</i> L.) possesses the highest lipid content among cereal crops, yet the functions of <i>PDAT</i> genes in this species remain largely unexplored. In this study, we identified and characterized three <i>AsPDAT</i> 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 <i>AsPDAT</i> genes share similar organ-specific and stress-responsive expression patterns, suggesting functional conservation following polyploidization, with <i>AsPDAT-5C</i> 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 <i>Nicotiana benthamiana</i> epidermal cells demonstrated that AsPDAT-5C localizes to the endoplasmic reticulum. Stable overexpression of <i>AsPDAT-5C</i> in <i>Nicotiana tabacum</i> 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.