Major contributor to triacylglycerol (TAG) synthesis and oil accumulation in seeds. Catalyzes the acylation of the sn-3 hydroxy group of sn-1,2-diacylglycerol using acyl-CoA (PubMed:10571850, PubMed:10580283, PubMed:10601854, PubMed:11402213, PubMed:12114588, PubMed:20040537, PubMed:20101470). Can use palmitoyl-CoA and oleoyl-CoA as substrates (PubMed:20101470). Can use oleoyl-CoA and linoleoyl-CoA as substrates. Has substrate preference for oleoyl-CoA compared to linoleoyl-CoA (PubMed:23770095). Has complementary functions with PDAT1 that are essential for triacylglycerol synthesis and normal development of both seeds and pollen (PubMed:20040537). a 1,2-diacyl-sn-glycerol + an acyl-CoA = a triacyl-sn-glycerol + CoA (9Z)-octadecenoyl-CoA + 1,2-di-(9Z-octadecenoyl)-sn-glycerol = 1,2,3-tri-(9Z-octadecenoyl)-glycerol + CoA Partially inhibited by niacin. Optimum pH is between 6.75-7.25. Glycerolipid metabolism; triacylglycerol biosynthesis. Interacts with LPCAT2 and LPAT2. Ubiquitous. Highest expression in young developing seeds. Peak of expression in seeds 15 days after flowering. Highly expressed in senescing leaves. Up-regulated by glucose (PubMed:12825687). Induced by abscisic acid (ABA), jasmonate, salicylate, salt and osmotic stress (PubMed:23942253). Decreased oil content and modified size and shape of oil bodies. The AS11 mutant has a complete duplication of exon 2. DGAT1 deficiency alters carbohydrate metabolism. Belongs to the membrane-bound acyltransferase family. Sterol o-acyltransferase subfamily.