Overexpression of McHB7 Transcription Factor from Mesembryanthemum crystallinum Improves Plant Salt Tolerance

Mesembryanthemum crystallinum (common ice plant) is one of the facultative halophyte plants, and it serves as a model for investigating the molecular mechanisms underlying its salt stress response and tolerance. Here we cloned one of homeobox transcription factor (TF) gene McHB7 from ice plant, which has 60% similarity with the Arabidopsis AtHB7. Overexpression of McHB7 in Arabidopsis (OE) showed that the plants had significantly elevated relative water content (RWC), chlorophyll content, superoxide dismutase (SOD) and peroxidase (POD) activities after salt stress treatment. Proteomics analysis identified 145 to be significantly changed in abundance, and 66 were exclusively increased in the OE plants compared to wild type (WT). After salt treatment, 979 and 959 metabolites were significantly increased and decreased in OE plants compared to the WT, respectively. The results demonstrated McHB7 can improve photosynthesis and increase the leaf chlorophyll content, and affect TCA cycle by regulating metabolites (e.g., pyruvate) and proteins (e.g., citrate synthase). Also, McHB7 modulates the expression of stress-related proteins (e.g., superoxide dismutase, dehydroascorbate reductase and pyrroline-5-carboxylate synthase B) to scavenge reactive oxygen species and enhance plant salt tolerance.

冰叶日中花（Mesembryanthemum crystallinum，俗称冰菜）是一类兼性盐生植物，可作为解析盐胁迫响应与耐受相关分子机制的模式植物。本研究从冰菜中克隆得到一个同源框转录因子（homeobox transcription factor, TF）基因McHB7，该基因与拟南芥AtHB7的序列相似性达60%。将McHB7在拟南芥中进行过表达（OE）后，经盐胁迫处理的转基因植株，其相对含水量（RWC）、叶绿素含量、超氧化物歧化酶（SOD）及过氧化物酶（POD）活性均显著升高。蛋白质组学分析结果显示，过表达植株与野生型（WT）相比，共有145个蛋白的丰度发生显著变化，其中66个蛋白仅在过表达植株中出现丰度上调。盐胁迫处理后，过表达植株相较于野生型，分别有979种和959种代谢物显著上调和下调。本研究结果表明，McHB7可通过调控代谢物（如丙酮酸）与蛋白（如柠檬酸合酶）影响三羧酸（TCA）循环；同时还可通过调控胁迫相关蛋白（如超氧化物歧化酶、脱氢抗坏血酸还原酶及吡咯啉-5-羧酸合酶B）的表达，清除活性氧，进而增强植株的耐盐性。