Submitted to: Recent Research Developments in Applied Microbiology and Biotechnology
Publication Type: Review article
Publication Acceptance Date: 3/24/2005
Publication Date: 6/30/2005
Citation: He, X., Chen, G.Q., Lin, J.T., Mckeon, T.A. 2005. Molecular characterization of the acyl-coa-dependent diacylglycerol acyltransferase in plants. Research Signpost: Recent Research Developments in Applied Microbiology and Biotechnology. 2:69-86. Interpretive Summary: Oil biosynthesis in plant is a complicated process, more than 30 reactions are required to convert acetyl-CoA to triacylglycerol. Many genes could control the quantity and quality of oil stored in a seed. The DGAT, which catalyzes the acylation reaction at the sn-3 position of the glycerol backbone, represents the only enzyme unique to the biosynthesis pathway of TAG . In many oilseeds, the profile of DGAT activity is closely correlated with oil accumulation, which confirms the role of DGAT in TAG synthesis. In addition, DGATs from several plant species showed pronounced selectivities for DAG and acyl-CoA, and this selectivity of the DGAT greatly influenced the type of TAG species formed in cells. Doubtless, the availability of multiple cloned genes for this enzyme, the capacity of the enzyme for channeling specific fatty acids to TAG, and the significant effect of the activity on oil yield have made the DGAT enzyme a new target for future development of new, high quantity and quality oils suitable for specific commercial utilizations, especially when used with other enzymes directing the synthesis of some unusual fatty acids.
Technical Abstract: The Acyl CoA:diacylglycerol (DGAT) is a membrane enzyme that catalyses the final step in TAG biosynthesis. Genes encoding this enzyme have been cloned from several plant species. Computer-based alignment of the coding sequences of the DGATs reveals that the DGAT is a highly conserved enzyme, with the most conserved regions in the C terminus. Southern blot analyses indicate that the genes encoding DGAT enzymes are only present as a single copy in many plant genomes. The transcripts of the DGAT gene are ubiquitous, but most abundant in maturing seeds in most plants. It is not necessary that the levels of the transcript and protein always have a direct linear correlation, but DGAT activity is predominantly a function of the level of DGAT protein. Studies on specificities of the DGAT enzyme for substrates demonstrated that the DGAT had pronounced selectivities for acyl donors and acyl acceptors with both 'common' and 'uncommon' fatty acids. A close correlation between DGAT activity and oil accumulation has been observed in numerous developing seeds. Transformation of plants with DGAT genes under both constitutive and seed specific promoters has demonstrated the feasibility of manipulating the oil content and composition among oilseed plants.