Abstract As antioxidants, tocopherols deactivate reactive oxygen species and prevent lipids from oxidation in response to abiotic stresses. γ-Tocopherol methyltransferase (γ-TMT) catalyzes the conversion of γ-tocopherol into α-tocopherol which has the highest biological activity. To investigate roles of γ-TMT in seed germination under salinity stress, we heterologously overexpressed an alfalfa MsTMT gene in Arabidopsis. MsTMT transgenic seeds germinated much slower than that of Arabidopsis wild-type (WT) seeds under salt stress or exogenous abscisic acid (ABA) treatment, indicating enhanced osmotic and ABA sensitivity in transgenic seeds. Under salinity stress, expression levels of ABA biosynthesis genes (NCED4 and NCED9) and signaling genes (ABI3 and ABI5) were increased in transgenic seeds. Meanwhile, the expression of GA biosynthesis genes (GA3OX1 and GA3OX2) were repressed and that of GA signal suppressor genes RGL2 was enhanced. Moreover, overexpression of MsTMT promoted the release of seed mucilage and contributed to the redistribution of pectins. Interestingly, removal of seed mucilage eliminated the difference in the initiation of seed germination between WT and transgenic lines. Taken together, MsTMT had a strong influence on the response to salinity stress in transgenic Arabidopsis during seed germination. Our results reveal a novel role of MsTMT in mediating the regulations of ABA and GA signaling in seed germination, which is also associated with mucilage release and structure. This study provides new insights into the regulatory network controlled by tocopherol biosynthesis gene in response to abiotic stress in plants.

中文翻译：

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苜蓿γ-生育酚甲基转移酶（γ-TMT）基因的过表达增加了转基因拟南芥种子萌发的盐敏感性

摘要 作为抗氧化剂，生育酚使活性氧失活并防止脂质因非生物胁迫而氧化。γ-生育酚甲基转移酶（γ-TMT）催化γ-生育酚转化为具有最高生物活性的α-生育酚。为了研究 γ-TMT 在盐胁迫下种子萌发中的作用，我们在拟南芥中异源过表达紫花苜蓿 MsTMT 基因。MsTMT 转基因种子在盐胁迫或外源脱落酸 (ABA) 处理下比拟南芥野生型 (WT) 种子发芽慢得多，表明转基因种子的渗透和 ABA 敏感性增强。在盐胁迫下，转基因种子中ABA生物合成基因（NCED4和NCED9）和信号基因（ABI3和ABI5）的表达水平增加。同时，GA生物合成基因（GA3OX1和GA3OX2）的表达受到抑制，GA信号抑制基因RGL2的表达增强。此外，MsTMT 的过表达促进了种子粘液的释放并有助于果胶的重新分配。有趣的是，去除种子粘液消除了 WT 和转基因品系之间种子萌发起始的差异。综上所述，MsTMT 对转基因拟南芥种子萌发过程中对盐分胁迫的反应有很大影响。我们的研究结果揭示了 MsTMT 在介导种子萌发过程中 ABA 和 GA 信号调节方面的新作用，这也与粘液释放和结构有关。这项研究提供了对生育酚生物合成基因控制的调控网络的新见解，以应对植物中的非生物胁迫。