College of Life Sciences, Ludong University, Yantai, Shandong, PR China.
College of Agriculture, Ludong University, Yantai, Shandong, PR China.
Tree Physiol. 2018 Oct 1;38(10):1566-1577. doi: 10.1093/treephys/tpy028.
Myo-inositol is a vital compound in plants. As the key rate-limiting enzyme in myo-inositol biosynthesis, l-myo-inositol-1-phosphate synthase (MIPS) is regarded as a determinant of the myo-inositol content in plants. The up-regulation of MIPS genes can increase the myo-inositol content, thereby enhancing the plant's resistance to a variety of stresses. However, there are few reports on the roles of myo-inositol and the identification of MIPS in woody trees. In this study, a MIPS gene, named as PeMIPS1, was characterized from Populus euphratica Oliv. The heterologous expression of PeMIPS1 compensated for inositol production in the yeast inositol auxotrophic mutant ino1 and the phenotypic lesions of the atmips1-2 mutant, an Arabidopsis MIPS1 knock-out mutant. A subcellular location analysis showed that the PeMIPS1-GFP fusion was localized in the nucleus and cytoplasm, but not in the chloroplasts, indicating that PeMIPS1 represented the cytosolic form of MIPS in P. euphratica. Interestingly, PeMIPS1 was not only inducible by drought and high salinity, but also by CuSO4 treatment. The transgenic poplar lines overexpressing PeMIPS1 had greater plant heights, shoot biomasses and survival rates than the wild type during the salt- or copper-stress treatment, and this was accompanied by an increase in the myo-inositol content. The overexpression of PeMIPS1 resulted in the increased activities of antioxidant enzymes and the accumulation of ascorbate, a key nonenzymatic antioxidant in plant, which partly accounted for the enhanced reactive oxygen species-scavenging capacity and the lowered hydrogen peroxide and malondialdehyde levels in the transgenic poplar. To the best of our knowledge, this study is the first to report the roles of MIPS genes in the tolerance to copper stress.
肌醇是植物中一种重要的化合物。作为肌醇生物合成的关键限速酶，L-肌醇-1-磷酸合酶（MIPS）被认为是植物肌醇含量的决定因素。MIPS 基因的上调可以增加肌醇含量，从而增强植物对各种胁迫的抗性。然而，关于肌醇的作用和 MIPS 在木本植物中的鉴定的报道很少。在这项研究中，从胡杨中鉴定了一个 MIPS 基因，命名为 PeMIPS1。异源表达 PeMIPS1 可补偿酵母肌醇营养缺陷型突变体 ino1 的肌醇合成，并补偿拟南芥 MIPS1 敲除突变体 atmips1-2 的表型缺陷。亚细胞定位分析表明，PeMIPS1-GFP 融合蛋白定位于细胞核和细胞质，但不在叶绿体中，表明 PeMIPS1 代表胡杨中的细胞质 MIPS 形式。有趣的是，PeMIPS1 不仅受干旱和高盐诱导，还受 CuSO4 处理诱导。过表达 PeMIPS1 的转基因杨树在盐或铜胁迫处理下的株高、地上部生物量和存活率均高于野生型，同时肌醇含量增加。过表达 PeMIPS1 导致抗氧化酶活性增加和抗坏血酸（植物中一种关键的非酶抗氧化剂）积累，这部分解释了转基因杨树中活性氧清除能力增强和过氧化氢及丙二醛水平降低的原因。据我们所知，这项研究首次报道了 MIPS 基因在耐受铜胁迫中的作用。
