Pectate lyases (PELs) play important roles in plant growth and development, mainly by degrading the pectin in primary cell walls. However, the role of PELs in cotton fiber elongation, which also involves changes in cellular structure and components, is poorly understood. Therefore, we aimed to isolate and characterize GhPEL76, as we suspected it to contribute to the regulation of fiber elongation. Expression analysis (qRT-PCR) revealed that GhPEL76 is predominately expressed in cotton fiber, with significantly different expression levels in long- and short-fiber cultivars, and that GhPEL76 expression is responsive to gibberellic acid and indoleacetic acid treatment. Furthermore, GhPEL76 promoter-driven β-glucuronidase activity was detected in the roots, hypocotyls, and leaves of transgenic Arabidopsis plants, and the overexpression of GhPEL76 in transgenic Arabidopsis promoted the elongation of several organs, including petioles, hypocotyls, primary roots, and trichomes. Additionally, the virus-induced silencing of GhPEL76 in cotton reduced fiber length, and both yeast one-hybrid and transient dual-luciferase assays suggested that GhbHLH13, a bHLH transcription factor that is up-regulated during fiber elongation, activates GhPEL76 expression by binding to the G-box of the GhPEL76 promoter region. Therefore, these results suggest GhPEL76 positively regulates fiber elongation and provide a basis for future studies of cotton fiber development.

中文翻译：

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果胶裂解酶样基因 GhPEL76 调控拟南芥器官伸长和棉花纤维伸长

果胶裂解酶 (PEL) 在植物生长和发育中发挥重要作用，主要是通过降解初级细胞壁中的果胶。然而，PELs 在棉纤维伸长中的作用还涉及细胞结构和成分的变化，我们知之甚少。因此，我们的目标是分离和表征 GhPEL76，因为我们怀疑它有助于调节纤维伸长。表达分析（qRT-PCR）显示 GhPEL76 主要在棉纤维中表达，在长纤维和短纤维品种中表达水平显着不同，并且 GhPEL76 表达对赤霉酸和吲哚乙酸处理有响应。此外，在转基因拟南芥植物的根、下胚轴和叶中检测到 GhPEL76 启动子驱动的 β-葡萄糖醛酸酶活性，GhPEL76 在转基因拟南芥中的过表达促进了几个器官的伸长，包括叶柄、下胚轴、初生根和毛状体。此外，病毒诱导的棉花中 GhPEL76 沉默减少了纤维长度，酵母单杂交和瞬时双荧光素酶测定表明 GhbHLH13，一种在纤维伸长过程中上调的 bHLH 转录因子，通过与 GhPEL76 结合激活 GhPEL76 表达。 GhPEL76 启动子区域的 G-box。因此，这些结果表明 GhPEL76 正向调节纤维伸长，并为未来棉纤维发育的研究提供基础。酵母单杂交和瞬时双荧光素酶测定表明 GhbHLH13，一种在纤维伸长过程中上调的 bHLH 转录因子，通过与 GhPEL76 启动子区域的 G 盒结合来激活 GhPEL76 表达。因此，这些结果表明 GhPEL76 正向调节纤维伸长，并为未来棉纤维发育的研究提供基础。酵母单杂交和瞬时双荧光素酶测定表明 GhbHLH13，一种在纤维伸长过程中上调的 bHLH 转录因子，通过与 GhPEL76 启动子区域的 G 盒结合来激活 GhPEL76 表达。因此，这些结果表明 GhPEL76 正向调节纤维伸长，并为未来棉纤维发育的研究提供基础。