欧亚国际

摘要

高温胁迫威胁着作物的生长和产量。碱性螺旋-环-螺旋（bHLH）转录因子（TF）已被证明在调节植物的高温抗性中发挥重要作用。然而，负责黄瓜耐高温性的bHLH转录因子尚未被确定。我们使用转录组分析来筛选黄瓜中的高温响应候选bHLH转录因子。在这里，我们发现75个CsbHLH基因的表达在高温胁迫下发生了改变。CsSPT基因在耐高温黄瓜植株中的表达是由高温诱导的。然而，通过CRISPR-Cas9系统获得的Csspt突变体植物表现出严重的热敏症状，包括枯萎的叶子和棕色的边缘，根密度和细胞活性降低。Csspt突变体植物在正常条件下也表现出H2O2水平升高和光系统相关基因下调。此外，Csspt突变体植物中存在较高的相对电解质渗漏（REC）、丙二醛（MDA）、谷胱甘肽（GSH）和超氧化物自由基（O2.-）水平，高温处理后脯氨酸含量降低。转录组分析表明，与野生型（WT）植物相比，Csspt突变体植物的光系统和叶绿体活性被高温胁迫严重破坏。此外，在高温胁迫下，Csspt突变体植物的植物激素信号转导以及MAPK和钙信号通路被激活。在高温条件下，HSF和HSP家族基因在Csspt和WT植物中具有相同的上调表达模式。然而，在Csspt突变体植物中，大多数bHLH、NAC和bZIP家族基因被热显著下调。因此，这些结果表明，CsSPT通过募集光合作用成分、信号通路分子和转录因子来调节高温反应。我们的研究结果为CsSPT在黄瓜中的热响应机制及其作为耐热作物育种靶标的潜力提供了重要的见解。

关键词

黄瓜bHLH CsSPT光合作用高温 

A bHLH transcription factor, CsSPT, regulates high-temperature resistance in cucumber

Abstract

High-temperature stress threatens the growth and yield of crops. Basic helix-loop-helix (bHLH) transcription factors (TFs) have been shown to play important roles in regulating high-temperature resistance in plants. However, the bHLH TFs responsible for high-temperature tolerance in cucumbers have not been identified. We used transcriptome profiling to screen the high temperature-responsive candidate bHLH TFs in cucumber. Here, we found that the expression of 75 CsbHLH genes was altered under high-temperature stress. The expression of the CsSPT gene was induced by high temperatures in TT (Thermotolerant) cucumber plants. However, the Csspt mutant plants obtained by the CRISPR-Cas9 system showed severe thermosensitive symptoms, including wilted leaves with brown margins and reduced root density and cell activity. The Csspt mutant plants also exhibited elevated H2O2 levels and down-regulated photosystem-related genes under normal conditions. Furthermore, there were high relative electrolytic leakage (REC), malondialdehyde (MDA), glutathione (GSH), and superoxide radical (O2.-) levels in the Csspt mutant plants, with decreased Proline content after the high-temperature treatment. Transcriptome analysis showed that the photosystem and chloroplast activities in Csspt mutant plants were extremely disrupted by the high-temperature stress compared with wild-type (WT) plants. Moreover, the plant hormone signal transduction, as well as MAPK and calcium signaling pathways were activated in Csspt mutant plants under high-temperature stress. The HSF and HSP family genes shared the same upregulated expression patterns in Csspt and WT plants under high-temperature conditions. However, most bHLH, NAC, and bZIP family genes were significantly down-regulated by heat in Csspt mutant plants. Thus, these results demonstrated that CsSPT regulated the high-temperature response by recruiting photosynthesis components, signaling pathway molecules, and transcription factors. Our results provide important insights into the heat response mechanism of CsSPT in cucumber and its potential as a target for breeding heat-resistant crops.

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