Weng Xun, Wang 王昊 Hao, Jiang Yifeng, Wang Ziheng, Chen Zhiheng, Liu Chuanhao, Yang Zhiyuan, Gao Jiayang, Jiang Liwen, Zhao Lifeng, Huang Jilei, Zhang Feng, Wang 王浩 Hao
Department of Cell and Developmental Biology, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
ZEISS Microscopy Customer Center, Beijing laboratory, Beijing 100084, China.
Sci Adv. 2025 Aug 22;11(34):eadw4550. doi: 10.1126/sciadv.adw4550. Epub 2025 Aug 20.
Plant fertilization relies on controlled pollen tube growth that integrates membrane dynamics and cell wall expansion. We previously identified an unconventional exocytic pathway wherein Golgi-derived secretory vesicles (GDSVs) bypass the trans-Golgi network to deliver pectin methylesterase 1 (NtPPME1), thereby modulating cell wall rigidity. However, the mechanisms linking this pathway with membrane dynamics and signaling remain elusive. Here, we used cryo-focused ion beam-scanning electron microscopy and three-dimensional tomography to identified GDSVs as a distinct vesicle population at the pollen tube tip. We further demonstrated that tobacco LORELEI-like glycosylphosphatidylinositol-anchored protein 4 (NtLLG4), a key signaling molecule controlling membrane dynamics and integrity, functions as a receptor for NtPPME1, regulating its polar exocytosis via GDSVs to control cell wall stiffness. Furthermore, we identified trafficking signals that direct the unconventional exocytosis of NtPPME1 across intracellular organelles. Our findings reveal a crucial mechanism coupling cell wall rigidity with membrane signaling to control pollen tube growth and integrity during fertilization.
植物受精依赖于可控的花粉管生长，这种生长整合了膜动力学和细胞壁扩张。我们之前鉴定出一种非常规的胞吐途径，其中高尔基体衍生的分泌囊泡（GDSVs）绕过反式高尔基体网络来递送果胶甲酯酶1（NtPPME1），从而调节细胞壁的刚性。然而，将该途径与膜动力学和信号传导联系起来的机制仍不清楚。在这里，我们使用冷冻聚焦离子束扫描电子显微镜和三维断层扫描来鉴定GDSVs是花粉管顶端一种独特的囊泡群体。我们进一步证明，烟草类LORELEI糖基磷脂酰肌醇锚定蛋白4（NtLLG4）是控制膜动力学和完整性的关键信号分子，作为NtPPME1的受体，通过GDSVs调节其极性胞吐作用以控制细胞壁硬度。此外，我们鉴定出指导NtPPME1跨细胞内细胞器进行非常规胞吐的运输信号。我们的研究结果揭示了一种关键机制，该机制将细胞壁刚性与膜信号传导耦合起来，以在受精过程中控制花粉管生长和完整性。
