Abstract Universal Stress Proteins (USPs) are ubiquitously responsive to environmental stresses, but function of most of them remains largely unknown. A novel USP from Medicago falcata (MfUSP1) was identified in the present study. MfUSP1 transcript is induced by low temperature, salinity, osmotic stress, abscisic acid (ABA) and H2O2. Overexpression of MfUSP1 resulted in increased tolerance to multiple abiotic stresses including freezing, salinity, osmotic stress, and methyl viologen (MV) induced oxidative stress. Higher activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate dependent peroxidase (APX) were observed in transgenic plants than in the wild type (WT) under the stressed conditions with lower reactive oxygen species (ROS) accumulation. Compared to WT, higher transcript levels of the genes encoding Cu, Zn-SOD, CAT, and APX were observed in transgenic plants under salinity and osmotic stress, and higher transcript levels of CAT and APX encoding genes under low temperature condition. Moreover, more proline was accumulated in transgenic plants than in WT under the stressed conditions, with upregulation of pyrroline-5-carboxylate synthetase 2 (P5CS2) and downregulation of proline oxidase 1 and 2 (PROX1 and PROX2). It is suggested that MfUSP1 confers tolerance to multiple abiotic stresses by regulating antioxidant defense and proline accumulation under stressed conditions.

中文翻译：

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来自苜蓿的通用应激蛋白 (MfUSP1) 通过调节抗氧化防御和脯氨酸积累赋予多重应激耐受性

摘要 通用应激蛋白 (USP) 普遍对环境应激做出反应，但其中大多数的功能仍然未知。在本研究中发现了一种来自 Medicago falcata (MfUSP1) 的新型 USP。MfUSP1 转录物由低温、盐度、渗透胁迫、脱落酸 (ABA) 和 H2O2 诱导。MfUSP1 的过表达导致对多种非生物胁迫的耐受性增加，包括冷冻、盐度、渗透胁迫和甲基紫精 (MV) 诱导的氧化胁迫。在活性氧 (ROS) 积累较低的应激条件下，转基因植物中的超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT) 和抗坏血酸依赖性过氧化物酶 (APX) 的活性高于野生型 (WT)。与 WT 相比，编码 Cu、Zn-SOD、CAT、在盐分胁迫和渗透胁迫下，转基因植物中观察到 APX 和 APX，低温条件下 CAT 和 APX 编码基因的转录水平较高。此外，在胁迫条件下，转基因植物中积累的脯氨酸比 WT 中的多，吡咯啉-5-羧酸合成酶 2（P5CS2）上调，脯氨酸氧化酶 1 和 2（PROX1 和 PROX2）下调。建议 MfUSP1 通过在压力条件下调节抗氧化防御和脯氨酸积累来赋予对多种非生物胁迫的耐受性。上调 pyrroline-5-carboxylate synthetase 2 (P5CS2) 和下调脯氨酸氧化酶 1 和 2（PROX1 和 PROX2）。建议 MfUSP1 通过在压力条件下调节抗氧化防御和脯氨酸积累来赋予对多种非生物胁迫的耐受性。上调 pyrroline-5-carboxylate synthetase 2 (P5CS2) 和下调脯氨酸氧化酶 1 和 2（PROX1 和 PROX2）。建议 MfUSP1 通过在压力条件下调节抗氧化防御和脯氨酸积累来赋予对多种非生物胁迫的耐受性。