Essential protein. Required for male and female gametophytes development (PubMed:26586834). Exhibits sn-1 acyltransferase activity with high specificity for acyl-coenzyme A, thus triggering storage lipid biosynthesis and playing an important role in the Kennedy pathway of glycerolipid biosynthesis (PubMed:27325892). Catalyzes triacylglycerol (TAG) accumulation involved in membrane lipid and oil biosynthesis, especially in seeds (PubMed:26586834, PubMed:27325892). Contributes also to the biosynthesis of both polar lipids and TAG in developing leaves, as well as lipid droplet production in developing pollen grains. Seems to not contribute to surface lipid biosynthesis (e.g. waxes and cutin) (PubMed:27325892). an acyl-CoA + sn-glycerol 3-phosphate = a 1-acyl-sn-glycero-3-phosphate + CoA Glycerolipid metabolism; triacylglycerol biosynthesis. Self-interacts. Interacts with LPAT2 and LPCAT2. Up-regulated during embryogenesis (PubMed:19539490, PubMed:27325892). Expressed in seedlings, leaves, stems, roots, floral buds, flowers, pollen, and siliques at various developmental stages (PubMed:27325892). Within siliques, accumulates strongly in developing embryos in the mid-stages of embryo development, during the time of abundant glycerolipid biosynthesis. In stems, confined to phloem and xylem. In flowers, mostly restricted to anthers (and more specifically pollen), and barely in sepals and petals. The HXXXXD motif is essential for acyltransferase activity and may constitute the binding site for the phosphate moiety of the glycerol-3-phosphate. Homozygous lethal. Male (pollen) and female gametophytic lethality. Reduces oil content and altered fatty acids (FA) composition. Belongs to the 1-acyl-sn-glycerol-3-phosphate acyltransferase family.