Overexpression of phospholipid: diacylglycerol acyltransferase in Brassica napus results in changes in lipid metabolism and oil accumulation

Abstract

The regulation of lipid metabolism in oil seeds is still not fully understood and increasing our knowledge in this regard is of great economic, as well as intellectual, importance. Oilseed rape (Brassica napus) is a major global oil crop where increases in triacylglycerol (TAG) accumulation have been achieved by overexpression of relevant biosynthetic enzymes. In this study, we expressed Arabidopsis phospholipid: diacylglycerol acyltransferase (PDAT1), one of the two major TAG-forming plant enzymes in B. napus DH12075 to evaluate its effect on lipid metabolism in developing seeds and to estimate its flux control coefficient. Despite several-fold increase in PDAT activity, seeds of three independently generated PDAT transgenic events showed a small but consistent decrease in seed oil content and had altered fatty acid composition of phosphoglycerides and TAG, towards less unsaturation. Mass spectrometry imaging of seed sections confirmed the shift in lipid compositions and indicated that PDAT overexpression altered the distinct heterogeneous distributions of phosphatidylcholine (PC) molecular species. Similar, but less pronounced, changes in TAG molecular species distributions were observed. Our data indicate that PDAT exerts a small, negative, flux control on TAG biosynthesis and could have under-appreciated effects in fine-tuning of B. napus seed lipid composition in a tissue-specific manner. This has important implications for efforts to increase oil accumulation in similar crops.

Comparative transcriptomic analysis provides insights into the genetic networks regulating oil differential production in oil crops

“…In addition, we found that genes encoding stearoyl-ACP desaturase were differentially expressed between high- and low-oil materials of crops, which differed in FA compositions, indicating its functional conservation among species as well as its potential to engineer specialized seed oil compositions. The consistency in differential expression of PDAT between high- and low-oil materials among species was also found in this study, suggesting its critical role in lipid accumulation, which has been demonstrated in individual species [ 10 , 53 ]. We also identified a conserved clique, including the coexpression relationship between PDAT , ABI3 , and other genes among oil crops.…”

Combined analysis of the metabolome and transcriptome provides insight into seed oil accumulation in soybean

“…In this work, LysoPC(18:0) was found to be positively associated with Glyma.10G119900 (GmGAPT) (r > 0.94, p < 1.73E-10). It is reported that LysoPC is the main component of fatty acid synthesis, and GmGAPT is related to TAG synthesis [42,43]. We also found that sphinganine was negatively associated with Glyma.06G172600 (GmGAPDH) (r < − 0.60, p < 0.004).…”

Combined analysis of the metabolome and transcriptome provides insight into seed oil accumulation in soybean

“…In this work, LysoPC(18:0) was found to be positively associated with Glyma.10G119900 ( GmGPAT ) ( r > 0.94, p < 1.73E-10). It is reported that LysoPC is the main component of fatty acid synthesis, and GmGPAT is related to TAG synthesis [ 43 , 44 ]. We also found that sphinganine was negatively associated with Glyma.06G172600 ( GmGAPDH ) (r < − 0.60, p < 0.004).…”