Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China.
J Cell Sci. 2020 Mar 18;133(6):jcs237404. doi: 10.1242/jcs.237404.
Self-incompatibility (SI) in the poppy triggers dramatic alterations in actin within pollen tubes. However, how these actin alterations are mechanistically achieved remains largely unexplored. Here, we used treatment with the Ca ionophore A23187 to mimic the SI-induced elevation in cytosolic Ca and trigger formation of the distinctive F-actin foci. Live-cell imaging revealed that this remodeling involves F-actin fragmentation and depolymerization, accompanied by the rapid formation of punctate actin foci and subsequent increase in their size. We established that actin foci are generated and enlarged from crosslinking of fragmented actin filament structures. Moreover, we show that villins associate with actin structures and are involved in this actin reorganization process. Notably, we demonstrate that VILLIN5 promotes actin depolymerization and formation of actin foci by fragmenting actin filaments, and controlling the enlargement of actin foci via bundling of actin filaments. Our study thus uncovers important novel insights about the molecular players and mechanisms involved in forming the distinctive actin foci in pollen tubes.
罂粟中的自交不亲和性（SI）会导致花粉管中肌动蛋白发生剧烈变化。然而，这些肌动蛋白变化是如何在机制上实现的，在很大程度上仍未得到探索。在这里，我们使用钙离子载体 A23187 处理来模拟 SI 诱导的细胞溶质 Ca 升高，并触发独特的 F-肌动蛋白焦点的形成。活细胞成像显示，这种重塑涉及 F-肌动蛋白的片段化和去聚合，伴随着点状肌动蛋白焦点的快速形成和随后的大小增加。我们确定肌动蛋白焦点是通过交联片段化的肌动蛋白丝结构而产生和扩大的。此外，我们表明，villins 与肌动蛋白结构相关，并参与这个肌动蛋白重排过程。值得注意的是，我们证明 VILLIN5 通过片段化肌动蛋白丝来促进肌动蛋白的解聚和肌动蛋白焦点的形成，并通过肌动蛋白丝的束集来控制肌动蛋白焦点的扩大。因此，我们的研究揭示了花粉管中形成独特肌动蛋白焦点的分子参与者和机制的重要新见解。
