Vernonia DGATs can complement the disrupted oil and protein metabolism in epoxygenase-expressing soybean seeds

Plant oils can be useful chemical feedstocks such as a source of epoxy fatty acids. High seed-specific expression of a Stokesia laevis epoxygenase (SlEPX) in soybeans only results in 3–7% epoxide levels. SlEPX-transgenic soybean seeds also exhibited other phenotypic alterations, such as altered seed fatty acid profiles, reduced oil accumulation, and variable protein levels. SlEPX-transgenic seeds showed a 2–5% reduction in total oil content and protein levels of 30.9–51.4%. To address these pleiotrophic effects of SlEPX expression on other traits, transgenic soybeans were developed to co-express SlEPX and DGAT (diacylglycerol acyltransferase) genes (VgDGAT1 & 2) isolated from Vernonia galamensis, a high accumulator of epoxy fatty acids. These side effects of SlEPX expression were largely overcome in the DGAT co-expressing soybeans. Total oil and protein contents were restored to the levels in non-transgenic soybeans, indicating that both VgDGAT1 and VgDGAT2 could complement the disrupted phenotypes caused by over-expression of an epoxygenase in soybean seeds.

► Expression of a Stokesia laevis epoxygenase (SlEPX) in soybeans achieves 3–7% epoxide levels.
► SlEPX-transgenic seeds showed a 2–5% reduction in oil and protein levels of 30.9–51.4%.
► These side effects were overcome with Vernonia galamensis DGAT1 and 2 coexpression.
► DGAT1 and 2 restored oil and protein contents to normal levels.
► DGAT1 and 2, especially 2 greatly increase epoxide accumulation in the oil.