Zhang Fei, Gao Xiuqing, Zhang Jingjie, Liu Baoling, Zhang Hongmei, Xue Jinai, Li Runzhi
College of Life Science, Shanxi Agricultural University, Taigu 030801, Shanxi, China.
Institute of Molecular Agriculture and Bioenergy, Shanxi Agricultural University, Taigu 030801, Shanxi, China.
Sheng Wu Gong Cheng Xue Bao. 2018 Sep 25;34(9):1478-1490. doi: 10.13345/j.cjb.180236.
Enhancing soybean (Glycine max) oil production is crucial to meet the market demand of vegetable oil. Diacylglycerol acyltransferase (DGAT) catalyzes the final acylation reaction of triacylglycerol (TAG) synthesis, acting as one of the rate-limiting enzymes for oil biosynthesis in plant seeds. Here, a cDNA clone VgDGAT1A encoding the DGAT1 protein was isolated from the high oil plant Vernonia galamensis. VgDGAT1A was specifically overexpressed in soybean seeds, and several high-generation transgenic lines (T7) were obtained by continuous selection. qPCR analysis showed that VgDGAT1A was highly expressed in the mid-development stage (30-45 DAF) of the transgenic seeds. Accordingly, the DGAT enzyme activity in the transgenic seeds was increased by 7.8 folds in comparison with the wild-type controls. Seed oil and starch contents were, respectively, increased by 5.1% (Dry weight) and reduced by 2%-3% in the transgenic soybeans. Importantly, protein content was not significantly different between transgenic and control seeds. Seed weight and germination rate of the transgenic lines exhibited no negative effect. Fatty acid profiling demonstrated that antioxidant oleic acid (C18:1Δ9) content in the transgenic seed oil was elevated by 8.2% compared to the control, and correspondingly, easily-oxidized linoleic acid (C18:2Δ9,12) and linolenic acid (C18:3Δ9,12,15) were decreased by 6% and 2% respectively. Taken together, seed-specific overexpression of an exogenous VgDGAT1A gene can break the negative linkage of oil and protein contents in soybean seeds, indicating that engineering of this highly-active DGAT enzyme is an effective strategy to improve oil yield and nutritional value in oilseeds.
提高大豆（Glycine max）油脂产量对于满足植物油市场需求至关重要。二酰甘油酰基转移酶（DGAT）催化三酰甘油（TAG）合成的最后酰化反应，是植物种子油脂生物合成的限速酶之一。在此，从高油植物银胶菊（Vernonia galamensis）中分离出一个编码DGAT1蛋白的cDNA克隆VgDGAT1A。VgDGAT1A在大豆种子中特异性过表达，并通过连续筛选获得了几个高世代转基因株系（T7）。qPCR分析表明，VgDGAT1A在转基因种子发育中期（开花后30 - 45天）高表达。相应地，转基因种子中的DGAT酶活性相较于野生型对照提高了7.8倍。转基因大豆种子的油脂和淀粉含量分别增加了5.1%（干重）和减少了2% - 3%。重要的是，转基因种子和对照种子之间的蛋白质含量没有显著差异。转基因株系的种子重量和发芽率没有受到负面影响。脂肪酸分析表明，转基因种子油中的抗氧化油酸（C18:1Δ9）含量相较于对照提高了8.2%，相应地，易氧化的亚油酸（C18:2Δ9,12）和亚麻酸（C18:3Δ9,12,15）分别降低了6%和2%。综上所述，外源VgDGAT1A基因在种子特异性过表达可以打破大豆种子中油脂和蛋白质含量的负相关联系，表明对这种高活性DGAT酶进行基因工程改造是提高油料作物油脂产量和营养价值的有效策略。
