In plants, glucose (Glc) plays important roles, as a nutrient and signal molecule, in the regulation of growth and development. However, the function of Glc in fiber development of upland cotton (Gossypium hirsutum) is unclear. Here, using gas chromatography-mass spectrometry (GC-MS), we found that the Glc content in fibers was higher than that in ovules during the fiber elongation stage. In vitro ovule culture revealed that lower Glc concentrations promoted cotton fiber elongation, while higher concentrations had inhibitory effects. The hexokinase inhibitor N-acetylglucosamine (NAG) inhibited cotton fiber elongation in the cultured ovules, indicating that Glc-mediated fiber elongation depends on the Glc signal transduced by hexokinase. RNA sequencing (RNA-seq) analysis and hormone content detection showed that 150mM Glc significantly activated brassinosteroid (BR) biosynthesis, and the expression of signaling-related genes was also increased, which promoted fiber elongation. In vitro ovule culture clarified that BR induced cotton fiber elongation in a dose-dependent manner. In hormone recovery experiments, only BR compensated for the inhibitory effects of NAG on fiber elongation in a Glc-containing medium. However, the ovules cultured with the BR biosynthetic inhibitor brassinazole and from the BR-deficient cotton mutant pag1 had greatly reduced fiber elongation at all the Glc concentrations tested. This demonstrates that Glc does not compensate for the inhibition of fiber elongation caused by BR biosynthetic defects, suggesting that the BR signaling pathway works downstream of Glc during cotton fiber elongation. Altogether, our study showed that Glc plays an important role in cotton fibre elongation, and crosstalk occurs between Glc and BR signaling during modulation of fiber elongation.

中文翻译：

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葡萄糖通过与油菜素内酯相互作用调节棉纤维伸长率

在植物中，葡萄糖 (Glc) 作为一种营养分子和信号分子，在调节生长和发育方面发挥着重要作用。然而，Glc 在陆地棉（Gossypium hirsutum）纤维发育中的作用尚不清楚。在这里，使用气相色谱-质谱（GC-MS），我们发现在纤维伸长阶段，纤维中的 Glc 含量高于胚珠中的 Glc 含量。体外胚珠培养表明，较低的 Glc 浓度促进棉纤维伸长，而较高浓度具有抑制作用。己糖激酶抑制剂 N-乙酰氨基葡萄糖 (NAG) 抑制培养胚珠中的棉花纤维伸长，表明 Glc 介导的纤维伸长取决于己糖激酶转导的 Glc 信号。RNA测序（RNA-seq）分析和激素含量检测表明，150mM Glc显着激活油菜素内酯（BR）的生物合成，同时信号相关基因的表达也增加，促进了纤维的伸长。体外胚珠培养阐明BR以剂量依赖性方式诱导棉花纤维伸长。在激素恢复实验中，在含 Glc 的介质中，只有 BR 补偿了 NAG 对纤维伸长的抑制作用。然而，用 BR 生物合成抑制剂芸苔素唑和来自 BR 缺陷型棉花突变体 pag1 培养的胚珠在所有测试的 Glc 浓度下都大大降低了纤维伸长率。这表明 Glc 不能补偿由 BR 生物合成缺陷引起的纤维伸长抑制，表明 BR 信号通路在棉花纤维伸长过程中在 Glc 下游起作用。总之，我们的研究表明，Glc 在棉花纤维伸长中起重要作用，并且在纤维伸长的调制过程中，Glc 和 BR 信号之间发生了串扰。