The present invention relates to the isolation, purification, characterization and use of the plant diacylglycerol acyltransferase (DGAT) gene and genetic products. The invention includes isolated and purified DGAT DNA and relates to methods of regulating seed oil content, the ratio of diacylglycerol/triacylglycerol proportions in the seed oil, fatty acid synthesis, seed oil acyl composition, seed size/weight and carbon flux into other seed components, using the gene, and to tissues and plants transformed with the gene. The invention also relates to transgenic plants, plant tissues and plant seeds having a genome containing an introduced DNA sequence of the invention, and a method of producing such plants and plant seeds.