Seitz Patricia L, Qu Li-Jia, Dresselhaus Thomas, Zhou Liang-Zi
Cell Biology and Plant Biochemistry, University of Regensburg, 93040, Regensburg, Germany.
State Key Laboratory for Gene Function and Modulation Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, New Cornerstone Science Laboratory, Peking University, Beijing, 100871, China.
Plant Reprod. 2025 Aug 28;38(3):18. doi: 10.1007/s00497-025-00528-y.
Recruitment of RALFs and LLGs for assembly at the apical plasma membrane of pollen tubes is orchestrated by ANXs/BUPSs through endomembrane trafficking.
Pollen tube growth requires precise regulation of cell wall integrity, which is maintained by ANX/BUPS-RALF-LLG signaling complexes. While structural and biochemical studies have revealed physical interactions between these components, their spatial organization and assembly dynamics in growing pollen tubes remain unclear. Here, we systematically investigated the subcellular localization and endomembrane trafficking of ANX/BUPS-RALF-LLG complex components through transient expression studies in tobacco pollen tubes. We demonstrate that each component exhibits distinct subcellular distribution patterns: RALF4/19 peptide ligands predominantly localize after secretion to the cell wall, ANXs/BUPSs receptors are enriched at the apical plasma membrane (PM), while GPI-anchored LLG2/3 co-receptors exclusively co-localize to cytosolic vesicles. Through co-expression studies, we show that ANXs/BUPSs recruit both RALFs and LLGs that localize to the same vesicles to the PM, indicating their role as master organizers and scaffolds of signaling complex assembly during pollen tube growth. RALFs stabilize ANX/BUPS-LLG interactions at the PM. Disruption of endocytosis by Brefeldin A treatment severely disrupts PM localization of ANXs/BUPSs and causes cytoplasmic aggregation of LLGs, while Wortmannin leads to partial trapping of proteins in pre-vacuolar compartments. Altogether, these findings indicate that ANX/BUPS-RALF-LLG complex assembly is highly dynamic and depends on proper endomembrane trafficking to maintain pollen tube integrity during growth.
The online version contains supplementary material available at 10.1007/s00497-025-00528-y.
通过内膜运输，ANXs/BUPSs精心安排RALFs和LLGs在花粉管顶端质膜上进行组装。
花粉管生长需要对细胞壁完整性进行精确调控，这由ANX/BUPS-RALF-LLG信号复合体维持。虽然结构和生化研究揭示了这些组分之间的物理相互作用，但它们在生长中的花粉管中的空间组织和组装动态仍不清楚。在这里，我们通过在烟草花粉管中的瞬时表达研究，系统地研究了ANX/BUPS-RALF-LLG复合体组分的亚细胞定位和内膜运输。我们证明每个组分都表现出不同的亚细胞分布模式：RALF4/19肽配体主要在分泌后定位于细胞壁，ANXs/BUPSs受体在顶端质膜（PM）富集，而糖基磷脂酰肌醇锚定的LLG2/3共受体仅共定位于胞质小泡。通过共表达研究，我们表明ANXs/BUPSs将定位于同一小泡的RALFs和LLGs都招募到质膜，表明它们在花粉管生长过程中作为信号复合体组装的主要组织者和支架的作用。RALFs稳定质膜上的ANX/BUPS-LLG相互作用。用布雷菲德菌素A处理破坏内吞作用会严重破坏ANXs/BUPSs的质膜定位，并导致LLGs的细胞质聚集，而渥曼青霉素会导致蛋白质部分滞留在液泡前区室中。总之，这些发现表明ANX/BUPS-RALF-LLG复合体组装是高度动态的，并且在生长过程中依赖于适当的内膜运输来维持花粉管的完整性。
在线版本包含可在10.1007/s00497-025-00528-y获取的补充材料。
