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SUMMARY: Acetyl‐triacylglycerols (acetyl‐TAG) contain an acetate group in the sn‐3 position instead of the long‐chain fatty acid present in regular triacylglycerol (TAG). The acetate group confers unique physical properties such as reduced viscosity and a lower freezing point to acetyl‐TAG, providing advantages for use as emulsifiers, lubricants, and 'drop‐in' biofuels. Previously, the synthesis of acetyl‐TAG in the seeds of the oilseed crop camelina (Camelina sativa) was achieved through the heterologous expression of the diacylglycerol acetyltransferase gene EaDAcT, isolated from Euonymus alatus seeds that naturally accumulate high levels of acetyl‐TAG. Subsequent work identified a similar acetyltransferase, EfDAcT, in the seeds of Euonymus fortunei, that possesses higher in vitro activity compared to EaDAcT. In this study, the seed‐specific expression of EfDAcT in camelina led to a 20 mol% increase in acetyl‐TAG levels over that of EaDAcT. Coupling EfDAcT expression with suppression of the endogenous competing enzyme DGAT1 further enhanced acetyl‐TAG accumulation, up to 90 mol% in the best transgenic lines. Accumulation of high levels of acetyl‐TAG was stable over multiple generations, with minimal effect on seed size, weight, and fatty acid content. Slight delays in germination were noted in transgenic seeds compared to the wild type. EfDAcT transcript and protein levels were correlated during seed development with a limited window of EfDAcT protein accumulation. In high acetyl‐TAG producing lines, EfDAcT protein expression in developing seeds did not reflect the eventual acetyl‐TAG levels in mature seeds, suggesting that other factors limit acetyl‐TAG accumulation. Significance statement: Acetyl‐TAGs are unusually structured triacylglycerols with useful properties synthesized by diacylglycerol acetyltransferase (DAcT) enzymes. The expression of a DAcT variant with increased activity, combined with suppression of endogenous storage lipid synthesis, resulted in the very high accumulation of acetyl‐TAG in transgenic Camelina sativa seed. However, DAcT protein expression did not correlate with acetyl‐TAG accumulation in mature seeds, suggesting that other factors limit acetyl‐TAG synthesis at very high levels. [ABSTRACT FROM AUTHOR]

SUMMARY: Brassica napus is an important oilseed crop in the world, and the mechanism of seed oil biosynthesis in B. napus remains unclear. In order to study the mechanism of oil biosynthesis and generate germplasms for breeding, an ethyl methanesulfonate (EMS) mutant population with ~100 000 M2 lines was generated using Zhongshuang 11 as the parent line. The EMS‐induced genome‐wide mutations in M2−M4 plants were assessed. The average number of mutations including single nucleotide polymorphisms and insertion/deletion in M2−M4 was 21 177, 28 675 and 17 915, respectively. The effects of the mutations on gene function were predicted in M2−M4 mutants, respectively. We screened the seeds from 98 113 M2 lines, and 9415 seed oil content and fatty acid mutants were identified. We further confirmed 686 mutants with altered seed oil content and fatty acid in advanced generation (M4 seeds). Five representative M4 mutants with increased oleic acid were re‐sequenced, and the potential causal variations in FAD2 and ROD1 genes were identified. This study generated and screened a large scale of B. napus EMS mutant population, and the identified mutants could provide useful genetic resources for the study of oil biosynthesis and genetic improvement of seed oil content and fatty acid composition of B. napus in the future. Significance Statement: Seed oil content and fatty acid composition are important traits of oil crop Brassica napus. In this study, a large number of Brassica napus EMS mutants with altered seed oil content or fatty acid composition have been generated and identified. This study provides useful genetic resources for functional genomics study and genetic improvement of B. napus. [ABSTRACT FROM AUTHOR]