UGT (UDP-dependent glycosyltransferase) family members are mainly involved in the modification of secondary metabolites, as well as plant stress responses. Previously, we identified the UGT gene MdUGT88F4 from Malus spp. In order to verify whether it had biological function in apple plants, we generated transgenic apple plants overexpressed MdUGT88F4 and treated them with salt stress. The results showed that it conferred enhanced salt stress tolerance in transgenic ‘GL-3’ apple (Malus domestica) plants. The expression of MdUGT88F4 was induced by salt stress, and overexpression of this gene alleviated the inhibitory effects of salt stress on the growth of apple plants. After 15 days of salt stress treatment (100 mmol·L−1 NaCl), necrotic spots were present on the leaves of wild-type (WT) plants, and none were observed on the leaves of transgenic plants overexpressing MdUGT88F4 (OX). The relative electrolyte leakage and malondialdehyde content were lower and the total chlorophyll content and the relative water content were higher in OX plants than in WT plants. The photosynthetic efficiency was higher in OX plants than in WT plants under salt stress, which was consistent with their larger stomatal aperture; this might stem from a reduction in the content of abscisic acid. The production of reactive oxygen species was lower and the activities of antioxidant enzymes were higher in OX plants than in WT plants. In addition, OX plants accumulated less Na+ but more K+ than WT plants, and the expression of several genes involved in Na + transport was upregulated in OX plants. MdUGT88F4 failed to promote the accumulation of isosalipurposide in vivo, and it was involved in isosalipurposide synthesis. Most of the flavonoid metabolites accumulated to a greater degree in OX plants than in WT plants. In summary, our results show that MdUGT88F4 positively regulates the salt stress response in apple plants, possibly by affecting stomatal movement, as well as the accumulation of ions and flavonoids. Our findings enhance our understanding of the metabolic mechanisms by which UGT proteins ameliorate the effects of salt stress in plants.

中文翻译：

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MdUGT88F4 参与异水利噗苷的合成正向调控苹果植株的盐胁迫反应


UGT （UDP 依赖性糖基转移酶） 家族成员主要参与次生代谢物的修饰以及植物胁迫反应。以前，我们从 Malus spp 中鉴定了 UGT 基因 MdUGT88F4。为了验证它在苹果植株中是否具有生物学功能，我们制备了过表达 MdUGT88F4 的转基因苹果植株，并对其进行盐胁迫处理。结果表明，它赋予转基因 'GL-3' 苹果 （Malus domestica） 植物更强的耐盐性。盐胁迫诱导 MdUGT88F4 的表达，该基因的过表达减轻了盐胁迫对苹果植株生长的抑制作用。盐胁迫处理 15 d（100 mmol·L−1 NaCl），野生型 （WT） 植物的叶片上存在坏死斑点，在过表达 MdUGT88F4 （OX） 的转基因植物的叶片上未观察到坏死斑点。OX 植株的相对电解质泄漏和丙二醛含量低于 WT 植株，总叶绿素含量和相对含水量高于 WT 植株。盐胁迫下 OX 植株的光合效率高于 WT 植株，这与它们较大的气孔孔径一致;这可能是由于脱落酸含量的降低。OX 植物活性氧的产生低于 WT 植物，抗氧化酶活性高于 WT 植物。此外，OX 植株积累的 Na + 比 WT 植株多，参与 Na + 转运的几个基因在 OX 植株中表达上调。MdUGT88F4 未能促进异水利噌苷在 体内的积累，参与异水利噌苷的合成。 大多数类黄酮代谢物在 OX 植物中的积累程度高于 WT 植物。综上所述，我们的结果表明，MdUGT88F4 可能通过影响气孔运动以及离子和类黄酮的积累，正向调节苹果植株的盐胁迫反应。我们的研究结果增强了我们对 UGT 蛋白改善植物盐胁迫影响的代谢机制的理解。