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<p>High temperature disrupts chlorophyll synthesis and chloroplast stability, decreasing chlorophyll content. However, the mechanism of high temperature inhibition chlorophyll synthesis remains unknown in horticultural plants. Here, we investigated the impact of high temperatures on the precursors and key genes involved in chlorophyll synthesis in cucumber leaves, including glutamate (Glu) and 5-aminolevulinic acid (ALA), along with enzymes such as glutamyl-tRNA reductase (GluTR). High temperatures inhibited the conversion of Glu to ALA, a critical step in chlorophyll synthesis, with GluTR playing a key role in this inhibition. Manipulating the expression of <i>CsGluTR1</i>, a gene coding for GluTR, showed that overexpression enhanced ALA synthesis and chlorophyll content under high-temperature stress in tobacco, and silencing <i>CsGluTR1</i> in cucumber plants had an opposite effect. The enhanced expression of <i>CsGluTR1</i> improved the net photosynthetic rate. Furthermore, CsMYB44 bound to the promoter of <i>CsGluTR1</i> and repressed its transcription under high temperatures to negatively regulate chlorophyll synthesis. In conclusion, high temperature induced the expression <i>CsMYB44</i>, which negatively affected <i>CsGluTR1</i> expression, leading to blocked chlorophyll synthesis and decreased chlorophyll content in cucumber.</p>

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MYB44 Negatively Regulates GluTR1 to Inhibit Chlorophyll Synthesis in Cucumber Under High Temperature

  • 期刊论文

  • 发表日期：

    2026年4月4日

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  • Yaohao Jia,
  • Zifeng Xie,
  • Fangting Xu,
  • Guangling Chen,
  • Jingjing He,
  • Xiaoying Liu,
  • Yu Wang,
  • Jin Sun

摘要

High temperature disrupts chlorophyll synthesis and chloroplast stability, decreasing chlorophyll content. However, the mechanism of high temperature inhibition chlorophyll synthesis remains unknown in horticultural plants. Here, we investigated the impact of high temperatures on the precursors and key genes involved in chlorophyll synthesis in cucumber leaves, including glutamate (Glu) and 5-aminolevulinic acid (ALA), along with enzymes such as glutamyl-tRNA reductase (GluTR). High temperatures inhibited the conversion of Glu to ALA, a critical step in chlorophyll synthesis, with GluTR playing a key role in this inhibition. Manipulating the expression of CsGluTR1, a gene coding for GluTR, showed that overexpression enhanced ALA synthesis and chlorophyll content under high-temperature stress in tobacco, and silencing CsGluTR1 in cucumber plants had an opposite effect. The enhanced expression of CsGluTR1 improved the net photosynthetic rate. Furthermore, CsMYB44 bound to the promoter of CsGluTR1 and repressed its transcription under high temperatures to negatively regulate chlorophyll synthesis. In conclusion, high temperature induced the expression CsMYB44, which negatively affected CsGluTR1 expression, leading to blocked chlorophyll synthesis and decreased chlorophyll content in cucumber.