Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2004
Publication Date: 4/1/2004
Citation: He, X., Chen, G.Q., Lin, J.T., Mckeon, T.A. 2004. Cloning and characterization of castor dgat. Lipids Journal.39:311-318
Interpretive Summary: In order to find new uses for vegetable oils in surplus, it is essential to develop alternative uses for them. One approach is to biochemically convert the oil to more valuable products. This paper reports the cloning of a gene for an enzyme that is essential in making castor oil, a vegetable oil with numerous industrial applications, including bio-based plastics, lubricants, bio-fuel additives and coatings. Currently, the domestic market consumes 110 million pounds of this strategically important oil, and it is all imported. The cloning of this gene supports development of biochemical means to produce alternative sources of castor oil. Ultimately, this research will result in domestic capability for castor oil production, expanding the availability of bio-based products.
Technical Abstract: The oil from castor seed (Ricinus communis) contains 90% ricinoleate, a hydroxy fatty acid that is an excellent source for producing numerous industrial products. Castor diacylglycerol acyltransferase (RcDGAT) is a critical enzyme as it catalyzes the terminal step in castor oil biosynthesis by preferentially incorporating ricinoleate into the triacylglycerols. We have isolated a cDNA encoding RcDGAT from developing castor seed. Analysis of the sequence reveals that this cDNA encodes a protein of 521 amino acids with a molecular mass of 59.9 KD and a predicted isoelectric point of 8.39. Expression of the full-length cDNA for RcDGAT in yeast Saccharomyces cerevisiae, strain INVSc1 results in a 7-fold higher DGAT activity compared to controls. Southern blot analysis indicates that the castor genome contains a single copy of the RcDGAT gene and analysis by RT-PCR reveals that the gene is expressed in the seed tissues. Accumulation of the RcDGAT mRNA reaches highest at 19 days after pollination and declines thereafter. Although there are regions of high homology to other plant DGAT coding sequences, there are sequence motifs that distinguish it as well. This work will facilitate the investigation of the substrate specificity of RcDGAT and provide the building materials for developing crops containing high levels of hydroxylated fatty acids.