Members of the bHLH family of transcription factors play important roles in multiple aspects of plant biological processes, for instance, abiotic stress responses. Previously, we characterized CaNAC035 a gene that positively regulates stress tolerance and identified CabHLH035, a CaNAC035-interacting protein in pepper (Capsicum annuum L.). In this study, we describe the role of CabHLH035 in the response to salt stress. Our results show that the expression of CabHLH035 increased following salt treatment. Transient expression of CabHLH035 (CabHLH035-To) in pepper enhanced salt tolerance, ectopic expression of CabHLH035 in Arabidopsis increased the salt stress tolerance, whereas knocking down the expression of CabHLH035 in pepper plants resulted in decreased salt tolerance. Homologs of the Salt Overly Sensitive 1 (SOS1) and pyrroline-5-carboxylate acid synthetase (P5CS) genes showed drastically increased expression in transgenic Arabidopsis plants expressing CabHLH035 and CabHLH035-To plants, but expression decreased in CabHLH035-silenced plants. Our results also showed that CabHLH035 can directly bind to the CaSOS1 and CaP5CS gene promoters and positively activate their expression. We found that transgenic Arabidopsis plants, ectopic expression of CabHLH035 and pepper plants transiently overexpressing CabHLH035 (CabHLH035-To) showed lower Na+ and higher proline contents in response to NaCl treatment, while CabHLH035-silenced plants had higher Na+ and lower proline concentrations. Overall, CabHLH035 plays important roles in salt tolerance through its effects on the intracellular Na+: K+ ratio and proline biosynthesis.

中文翻译：

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辣椒 bHLH 转录因子 CabHLH035 通过调节离子稳态和脯氨酸生物合成促进耐盐性

bHLH 转录因子家族的成员在植物生物过程的多个方面发挥着重要作用，例如，非生物胁迫反应。此前，我们对 CaNAC035 进行了表征，该基因正向调节胁迫耐受性，并鉴定了辣椒 (Capsicum annuum L.) 中的 CaNAC035 相互作用蛋白 CabHLH035。在这项研究中，我们描述了 CabHLH035 在响应盐胁迫中的作用。我们的结果表明，盐处理后 CabHLH035 的表达增加。CabHLH035（CabHLH035-To）在辣椒中的瞬时表达增强了耐盐性，CabHLH035在拟南芥中的异位表达增加了耐盐性，而在辣椒中敲低CabHLH035的表达导致耐盐性降低。盐过度敏感 1 (SOS1) 和吡咯啉-5-羧酸合成酶 (P5CS) 基因的同系物在表达 CabHLH035 和 CabHLH035-To 植物的转基因拟南芥植物中表现出显着增加的表达，但在 CabHLH035 沉默的植物中表达减少。我们的结果还表明，CabHLH035 可以直接结合 CaSOS1 和 CaP5CS 基因启动子并积极激活它们的表达。我们发现转基因拟南芥植物、异位表达 CabHLH035 和瞬时过表达 CabHLH035 (CabHLH035-To) 的辣椒植物响应于 NaCl 处理显示出较低的 Na+ 和较高的脯氨酸含量，而 CabHLH035 沉默的植物具有较高的 Na+ 和较低的脯氨酸浓度。总体而言，CabHLH035 通过其对细胞内 Na+ 的影响在耐盐性中发挥重要作用：