Identification and Functional Analysis of Avocado DGAT1 and DGAT2 Expressed in Yeast

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The avocado mesocarp contains up to 60-70% oil by dry weight where triacylglycerol (TAG) is the major constituent. This neutral lipid, TAG is utilized by plants for the carbon and energy source when stores in seed tissue. There is significant human nutritional demand for vegetable oil, but its use in production of renewable biomaterials and fuels has intensified the need to increase oil production. In plants, the final and committed step in TAG biosynthesis is catalyzed by diacylglycerol acyltransferases (DGAT) and/or a phospholipid: diacylglycerol acyltransferases (PDAT). Both DGAT and PDAT contribute to seed TAG biosynthesis in an independent or overlapping manner, depending on the species. However, the regulation of TAG biosynthesis is not well-studied in nonseed tissues such as mesocarp of avocado. Based on the transcriptome data of Persea americana it is hypothesized that both DGAT and PDAT are likely to catalyze the conversion of diacylglycerol to TAG. In this study, putative DGAT1 and DGAT2 were identified and comprehensive in silico analyses were conducted to determine the respective start codons, full-length coding sequences, transmembrane domains, predicted protein structures and phylogenetic relationships with other known DGATs. These data reveal that the putative DGATs of a basal angiosperm species retain features that are conserved not only among angiosperms but also other eukaryotes. For further functional analysis, the avocado DGATs were expressed in H1246, a TAG-deficient yeast strain and lipotoxicity rescue assays were conducted. The complementation of this yeast strain confirmed enzyme activity and supported the possible role of both avocado DGATs in TAG biosynthesis. Future studies will be focused on determining the substrate specificity of DGAT and its role, relative to PDATs in TAG biosynthesis in avocado mesocarp.


Johnson City, TN

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