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我校学者破解棉花化学脱叶分子密码,助力机械采收“叶净铃丰”

南湖新闻网讯(通讯员 张冰)如何让棉花“聪明”落叶,同时保障棉花稳产?近日,我校棉花遗传改良团队在Molecular Plant期刊发表突破性成果“RAPID LEAF FALLING 1 facilitates chemical defoliation and mechanical harvesting in cotton”。该研究首次揭示化学脱叶剂诱导棉花叶片脱落的核心分子机制,并成功创制“减药不减效”的新型棉花种质,为提升机采棉品质、推动农业绿色发展提供关键技术支撑。

棉花机械化采收是现代农业发展的重要方向,但叶片残留导致的纤维含杂问题长期制约采收品质。在棉花机械化采收前,化学脱叶剂通过诱导叶片脱落,可显著减少机械采收时的杂质污染。然而,过量使用脱叶剂易引发棉铃发育受损,导致减产。如何平衡脱叶效率与产量,成为世界棉花主产国共同面临的难题。研究团队以我国机采棉品种“新陆早50号”为材料,通过细胞学观察发现,叶柄基部存在约包含10层细胞的脱落区,在一定浓度脱叶剂处理48小时后,棉花植株的功能叶的叶柄基部从此区域发生断裂,脱离植株母体。为解析这一过程的分子机制,团队采用单核转录组测序技术(snRNA-seq),首次绘制了棉花叶柄脱落区的高分辨率细胞图谱,成功捕获超过10万个细胞核的基因表达信息。

数据分析揭示,脱叶剂处理后,叶柄脱落区动态形成两类新型功能细胞——“脱落细胞”和“保护层细胞”。同时,团队锁定关键基因GhRLF1(RAPID LEAF FALLING 1),其编码的细胞分裂素氧化酶可降解叶片脱落区的细胞分裂素,触发脱落信号。实验显示,GhRLF1过表达株系在脱叶剂处理72小时后,叶片脱落率高达95%,而敲除突变体株系仅50%,证实其核心调控作用。

研究进一步发现,脱叶剂通过激活“先锋者”转录因子GhWRKY70,驱动GhRLF1的早期表达;48小时后,另一“后继者”转录因子GhMYB108接力启动GhRLF1的持续表达,形成级联调控网络。这种“双因子接力”模式,确保细胞分裂素水平持续下降,从而精确控制叶片脱落时序。为验证这一机制,团队构建了GhWRKY70与GhMYB108的转基因株系。结果显示,GhWRKY70过表达株系对脱叶剂敏感性显著提高,而抑制株系则表现出明显抗性;GhMYB108的调控效应与之类似,但作用时间延后。这一发现不仅揭示脱叶剂作用的分子时序逻辑,更为精准调控脱叶进程提供了关键靶点。

尽管GhRLF1可显著提升脱叶效率,但其在棉铃等器官的过量表达会导致细胞分裂素水平异常,引发棉铃发育受阻、产量下降。如何实现“叶净铃丰”?团队筛选到proGhPER21启动子——仅在脱叶剂处理的叶柄脱落区特异性激活,而在棉铃等组织中几乎不表达。通过分子设计,团队将proGhPER21启动子与GhRLF1基因耦合,创制出proPER21::RLF1转基因棉花。田间试验表明,该材料在70%脱叶剂用量下,脱叶效率仍优于100%脱叶剂处理下的野生型,且棉铃数量、皮棉产量均未受影响,成功破解“脱叶与增产难以兼得”的产业难题。

此项研究首次从单细胞层面解析棉花化学脱叶的分子机制,实现了三大创新突破。在理论层面,揭示了细胞分裂素代谢调控叶片脱落的新通路,补充了以“乙烯-生长素”主导的理论框架;在技术层面,筛选出叶柄脱落区特异性响应的proGhPER21启动子,为作物性状精准调控提供通用工具;在应用层面,培育出“少用药、高脱叶、稳产量”的棉花新种质,推动化学脱叶从“经验施药”迈向“智能调控”。

目前,研究团队正进一步优化proGhPER21启动子的响应效率,并积极探索其他重要调控新机制,努力实现叶柄脱落区更为精确激活,实现药剂零浪费。随着全球农业绿色转型加速,该项技术不仅为我国棉花产业提质增效注入新动能,更为减少化学投入、保障粮食安全提供了中国方案。

华中农业大学博士研究生张冰和岳丹丹为共同第一作者,我校杨细燕教授、张献龙院士和新疆农垦科学院余渝研究员为通讯作者。

审核人 杨细燕

论文链接:http://www.cell.com/molecular-plant/fulltext/S1674-2052(25)00107-8

【英文摘要】

Chemical defoliation stands as the ultimate tool in enabling the mechanical harvest of cotton, offering economic and environmental advantages. However, the underlying molecular mechanism that triggers leaf abscission through defoliant remains unsolved. In this study, through single-nucleus mRNA sequencing (snRNA-seq) of the abscission zone (AZ) from cotton petiole, we meticulously constructed a transcriptomic atlas and identified two newly-formed cell types, abscission cells and protection layer cells in cotton petiole AZ after defoliant treatment. GhRLF1 (RAPID LEAF FALLING 1), as one of the members encoding cytokinin oxidase/dehydrogenase (CKX) gene family, was identified as key marker gene unique to the abscission cells following defoliant treatment. Overexpression of GhRLF1 resulted in reduced cytokinin accumulation and accelerated leaf abscission. Conversely, CRISPR/Cas9-mediated loss of GhRLF1 function appeared to delay this process. Its interacting regulators, GhWRKY70, acting as "Pioneer" activator, and GhMYB108, acting as "Successor" activator, orchestrate a sequential modulation GhWRKY70/GhMYB108-GhRLF1-cytokinin (CTK) within the AZ to regulate cotton leaf abscission. GhRLF1 not only regulates leaf abscission but also reduces cotton yield. Consequently, transgenic lines exhibiting rapid leaf falling and requiring less defoliant, while maintaining unaffected cotton yield, were developed for mechanical harvesting. This was achieved using a defoliant-induced petiole-specific promoter proPER21, to drive GhRLF1 (proPER21::RLF1). This pioneering biotechnology offers a new strategy for the chemical defoliation of machine-harvested cotton, ensuring stable production and reducing leaf debris in harvested cotton, thereby enhancing environmental sustainability.

 

 

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