Abstract High mobility group (HMG) proteins play an important role in plant responses to abiotic stresses. However, to date, few studies have focused on the functional characterization of HMG genes in woody plants. In this study, 11 BpHMG genes named BpHMG1-BpHMG11 were cloned and characterized from Betula platyphylla. The expression patterns of BpHMG genes under two types of abiotic stress (osmotic and salt stress) and ABA (abscisic acid) treatments were detected by qRT-PCR. The results showed that the expression of 11 BpHMG genes in birch roots, stems and leaves changed in at least one stress treatment time point under all three treatments, suggesting that 11 BpHMG genes could respond to salt, osmotic stress and ABA treatment. In particular, the expression of BpHMG6 in birch stems was significantly upregulated at all studied time points under NaCl stress. The highest level was increased up to 118-fold compared with the control, indicating that this gene may be involved in salt stress responses. To further study the salt tolerance function of BpHMG6, the overexpression vector pROKII-BpHMG6 and silencing expression vector pFGC-BpHMG6 were constructed and transiently transformed into birch. The empty vector pROKII was also transformed as a control. POD activity, H2O2 and MDA levels, relative electrolyte and NBT, DAB and Evans blue staining were analysed and compared between transgenic and control plants under salt stress. The results indicated that the overexpression of BpHMG6 in birch not only increased the activity of protective enzymes under salt stress but also enhanced the ROS scavenging capacity to reduce cell damage and death caused by salt stress. Conversely, the silenced transiently transformed plants displayed the opposite physiological changes. Therefore, BpHMG6 potentially plays a role in salt stress tolerance in transgenic birch plants.

中文翻译：

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白桦耐盐HMG基因的筛选及功能鉴定

摘要 高迁移率群 (HMG) 蛋白在植物对非生物胁迫的响应中起重要作用。然而，迄今为止，很少有研究关注木本植物中 HMG 基因的功能表征。本研究从白桦中克隆并表征了11个BpHMG基因，命名为BpHMG1-BpHMG11。通过qRT-PCR检测BpHMG基因在两种非生物胁迫（渗透胁迫和盐胁迫）和ABA（脱落酸）处理下的表达模式。结果表明，3个处理下，桦树根、茎和叶中11个BpHMG基因的表达量在至少一个胁迫处理时间点发生变化，表明11个BpHMG基因可以响应盐分、渗透胁迫和ABA处理。特别是，在 NaCl 胁迫下的所有研究时间点，桦树茎中 BpHMG6 的表达均显着上调。与对照相比，最高水平增加了 118 倍，表明该基因可能参与了盐胁迫反应。为进一步研究BpHMG6的耐盐功能，构建了过表达载体pROKII-BpHMG6和沉默表达载体pFGC-BpHMG6并瞬时转化桦木。空载体 pROKII 也被转化为对照。分析并比较盐胁迫下转基因植物和对照植物之间的 POD 活性、H2O2 和 MDA 水平、相对电解质和 NBT、DAB 和伊文思蓝染色。结果表明，桦树中BpHMG6的过表达不仅增加了盐胁迫下保护酶的活性，而且增强了ROS清除能力，以减少盐胁迫引起的细胞损伤和死亡。相反，沉默的瞬时转化植物表现出相反的生理变化。因此，BpHMG6 可能在转基因桦树植物的盐胁迫耐受性中发挥作用。