Regulation of membrane fusion during cytokinesis - specificity and redundancy of SNARE complexes and regulatory SM proteins

植物胞质分裂在力学上不同于非植物真核生物的胞质分裂，高尔基体/TGN来源的膜泡经过同型融合形成两个子核之间的分隔膜。虽然拟南芥中一种植物特有的、胞质分裂特异的合成素Knolle已被确定为胞质分裂中膜融合的主要调节因子，但它的敲除仍然允许胚胎发生的完成。相反，缺乏Knolle和其调控的SM蛋白keule的双重突变体在受精卵阶段就不能进行胞质分裂，这表明在胞质分裂过程中Synaxins和SM蛋白都存在功能冗余。这项建议旨在确定“后备”制度。可能的候选基因是SYP1Synaxin SYP132和与Keule、SEC1A和SEC1B相近的同源基因。我们将结合使用遗传分析、免疫共沉淀、亚细胞定位和酵母双杂交分析来进行实验来测试这一想法。这些实验旨在揭示SNARE复合体及其在细胞质分裂中的需求，以及SM蛋白对它们的调节。我们还将对苔藓Physcomitrella进行功能研究，以探索在开花植物中运行的细胞质分裂机制的进化起源。

Plant cytokinesis is mechanistically different from cytokinesis in non-plant eukaryotes, with Golgi/TGN-derived membrane vesicles undergoing homotypic fusion to form the partitioning membrane between the two daughter nuclei. Although a plant-specific and cytokinesis-specific syntaxin named KNOLLE in Arabidopsis has been identified as a major regulator of membrane fusion in cytokinesis, its knockout still allows for the completion of embryogenesis. In contrast, a double mutant lacking both KNOLLE and its regulatory SM protein KEULE fails to undergo cytokinesis already at the zygote stage, suggesting functional redundancy of both syntaxins and SM proteins in cytokinesis. This proposal aims to identify the "back-up" system. Likely candidates are the SYP1 syntaxin SYP132 and the close paralogues of KEULE, SEC1A and SEC1B. We will perform experiments to test this idea, using a combination of genetic analysis, co-immunoprecipitation, subcellular localisation and yeast two-hybrid interaction assays. These experiments are to reveal SNARE complexes and their requirements in cytokinesis as well as their regulation by SM proteins in Arabidopsis. We will also perform functional studies in the moss Physcomitrella to explore the evolutionary origin of the cytokinesis machinery that operates in flowering plants.