Salt and drought are the main abiotic stresses that restrict the yield of crops. Peroxidases (PRXs) are involved in various abiotic stress responses. Furthermore, only few wheat PRXs have been characterized in the mechanism of the abiotic stress response. In this study, a novel wheat peroxidase (PRX) gene named TaPRX-2A, a member of wheat class III PRX gene family, was cloned and its response to salt stress was characterized. Based on the identification and evolutionary analysis of class III PRXs in 12 plants, we proposed an evolutionary model for TaPRX-2A, suggesting that occurrence of some exon fusion events during evolution. We also detected the positive selection of PRX domain in 13 PRXs involving our evolutionary model, and found 2 or 6 positively selected sites during TaPRX-2A evolution. Quantitative reverse transcription–polymerase chain reaction (qRT–PCR) results showed that TaPRX-2A exhibited relatively higher expression levels in root tissue than those exhibited in leaf and stem tissues. TaPRX-2A expression was also induced by abiotic stresses and hormone treatments such as polyethylene glycol 6000, NaCl, hydrogen peroxide (H2O2), salicylic acid (SA), methyljasmonic acid (MeJA) and abscisic acid (ABA). Transgenic wheat plants with overexpression of TaPRX-2A showed higher tolerance to salt stress than wild-type (WT) plants. Confocal microscopy revealed that TaPRX-2A-eGFP was mainly localized in cell nuclei. Survival rate, relative water content, and shoot length were higher in TaPRX-2A-overexpressing wheat than in the WT wheat, whereas root length was not significantly different. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced in TaPRX-2A-overexpressing wheat compared with those in the WT wheat, resulting in the reduction of reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) content. The expression levels of downstream stress-related genes showed that RD22, TLP4, ABAI, GST22, FeSOD, and CAT exhibited higher expressions in TaPRX-2A-overexpressing wheat than in WT under salt stress. The results show that TaPRX-2A plays a positive role in the response to salt stress by scavenging ROS and regulating stress-related genes.

中文翻译：

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小麦III类过氧化物酶基因家族成员TaPRX-2A具有增强盐胁迫耐受性的作用。


盐和干旱是限制作物产量的主要非生物胁迫。过氧化物酶（PRX）参与各种非生物胁迫反应。此外，只有少数小麦 PRX 在非生物胁迫反应机制中得到了表征。本研究克隆了小麦III类PRX基因家族中的一个新的小麦过氧化物酶（PRX）基因TaPRX-2A，并表征了其对盐胁迫的响应。基于12种植物中III类PRX的鉴定和进化分析，我们提出了TaPRX-2A的进化模型，表明在进化过程中发生了一些外显子融合事件。我们还在涉及我们的进化模型的13个PRX中检测到了PRX结构域的正选择，并在TaPRX-2A进化过程中发现了2或6个正选择位点。定量逆转录聚合酶链反应（qRT-PCR）结果表明，TaPRX-2A在根组织中的表达水平高于叶和茎组织中的表达水平。非生物胁迫和激素处理（例如聚乙二醇 6000、氯化钠、过氧化氢 (H2O2)、水杨酸 (SA)、甲基茉莉酸 (MeJA) 和脱落酸 (ABA)）也会诱导 TaPRX-2A 表达。过度表达 TaPRX-2A 的转基因小麦植物比野生型 (WT) 植物表现出更高的盐胁迫耐受性。共聚焦显微镜显示TaPRX-2A-eGFP主要位于细胞核中。 TaPRX-2A过表达小麦的成活率、相对含水量和地上部长度均高于WT小麦，而根长度没有显着差异。 与WT小麦相比，过表达TaPRX-2A的小麦中超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性增强，导致活性氧（ROS）积累和丙二醛减少（MDA）内容。下游胁迫相关基因的表达水平显示，在盐胁迫下，RD22、TLP4、ABAI、GST22、FeSOD和CAT在TaPRX-2A过表达小麦中的表达量高于WT。结果表明，TaPRX-2A通过清除ROS、调控应激相关基因，在应对盐胁迫中发挥积极作用。