Improving soybean (Glycine max) seed composition by increasing the protein and oil components will add significant value to the crop and enhance environmental sustainability. Diacylglycerol acyltransferase (DGAT) catalyzes the final rate-limiting step in triacylglycerol (TAG) biosynthesis and has a major impact on seed oil accumulation. We previously identified a soybean DGAT1b variant with 14 amino acid substitutions (GmDGAT1b-MOD) that increases total oil content by 3 percentage points when overexpressed in soybean seeds. In the present study, additional GmDGAT1b variants were generated to further increase oil with a reduced number of substitutions. Variants with one to four amino acid substitutions were screened in the model systems S. cerevisiae and transient N. benthamiana leaf. Promising GmDGAT1b variants resulting in high oil accumulation in the model systems were selected for over-expression in soybeans. One GmDGAT1b variant with three novel amino acid substitutions (GmDGAT1b-3aa) increased total soybean oil to levels near the previously discovered GmDGAT1b-MOD variant. In a multiple location field trial, GmDGAT1b-3aa transgenic events had significantly increased oil and protein by up to 2.3 and 0.6 percentage points, respectively. Modeling of the GmDGAT1b-3aa protein structure provided insights into the potential function of the three substitutions. These findings will guide efforts to improve soybean oil content and overall seed composition by CRISPR editing.

中文翻译：

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具有三个氨基酸取代的新型大豆二酰甘油酰基转移酶 1b 变体可提高种子油含量

通过增加蛋白质和油成分来改善大豆 (Glycine max) 种子成分将为作物增加显着价值并增强环境可持续性。二酰基甘油酰基转移酶 (DGAT) 催化三酰基甘油 (TAG) 生物合成的最后限速步骤，并对种子油积累产生重大影响。我们之前发现了一种具有 14 个氨基酸取代的大豆 DGAT1b 变体 (GmDGAT1b-MOD)，当在大豆种子中过度表达时，总油含量会增加 3 个百分点。在本研究中，生成了额外的 GmDGAT1b 变体，以通过减少取代数量进一步增加石油含量。在模型系统酿酒酵母和瞬时烟草叶中筛选了具有一到四个氨基酸取代的变体。选择在模型系统中导致高油积累的有前景的 GmDGAT1b 变体用于在大豆中过度表达。具有三个新氨基酸取代的 GmDGAT1b 变体 (GmDGAT1b-3aa) 将大豆油总量增加到接近先前发现的 GmDGAT1b-MOD 变体的水平。在多地点现场试验中，GmDGAT1b-3aa 转基因事件使油和蛋白质分别显着增加了 2.3 和 0.6 个百分点。GmDGAT1b-3aa 蛋白质结构的建模提供了对三种取代的潜在功能的深入了解。这些发现将指导通过 CRISPR 编辑提高大豆油含量和整体种子成分的努力。