Investigation of the contribution of oil biosynthetic enzymes to seed oil content in Brassica napus and Arabidopsis thaliana

One of the critical reactions in triacylglycerol (TAG) biosynthesis is activation of fatty acyl chains to fatty acyl CoAs, catalyzed by long-chain acyl CoA synthetases (LACS). In Arabidopsis thaliana there is a family of nine genes that encode LACSs. Studies to determine whether the products of two of these genes, LACS8 and LACS9, function together to contribute acylCoAs for storage oil biosynthesis in A. thaliana resulted in discovery that it is not LACS8 but LACS1 that functionally overlaps with LACS9 in TAG biosynthesis (published in Plant Journal). To elucidate regulatory mechanisms of seed oil synthesis, the potential roles of phospholipase D zeta (PLDZ) and rhamnose synthase 2 (RHM2/ MUM4) in transcription factor GLABRA2 (GL2)-mediated regulation of seed oil biosynthesis and deposition were investigated. Results demonstrated that PLDZ genes are not involved in GL2-mediated seed oil accumulation and that GL2 regulates seed oil production, at least in part, through its influence on expression of the gene RHM2/ MUM4 required for the seed coat mucilage biosynthesis (published in Plant Journal). A novel Arabidopsis mutant with speckled seed coat and reduced seed oil phenotypes resulting from a mutation in a single unknown gene was identified, but attempts to isolate the gene by positional cloning have not been successful to date (unpublished results). Finally, seed oil content in near-isogenic double haploid Brassica napus lines was analyzed, "low oil'' and "high oil'' lines were identified, and developing seeds for expression profiling of target seed oil biosynthesis/bioassembly genes in selected double haploid lines were collected (unpublished results).