Mechanistic Insights Into Chloroplast FtsZ Assembly and Dynamics

植物拥有被称为叶绿体的特殊隔间，使它们能够直接从太阳获取光能，并通过光合作用将其转化为化学能。光合作用产生有机化合物，构成全球食物链的基础，对农业生产至关重要。当植物细胞在叶片生长过程中扩张时，它们的叶绿体数量在分裂过程中急剧增加，这对提高光合作用能力至关重要。与蓝藻的起源一致，叶绿体从它们的原核生物祖先的细胞分裂机制中遗传了几个分裂机制的组件。其中最重要的是一种名为FtsZ的细胞骨架蛋白。在细菌和叶绿体中，FtsZ蛋白组装成聚合物，在细胞或细胞器的中心形成一个环，称为“Z环”，这有助于推动分裂过程的紧缩力。这个项目试图洞察叶绿体如何在分裂中使用这些蛋白质，并寻求更好地理解叶绿体和原核分裂之间的差异。更广泛的影响活动将包括参加密歇根州立大学女童子军STEM演示日，该日为全州各地的女孩提供动手示范和活动。此外，一名博士后将参与更新和扩展关于叶绿体生物学的维基百科页面，以帮助普通公众更好地了解叶绿体是如何工作的。细菌细胞分裂只需要一种类型的FtsZ，而叶绿体分裂需要两种不同类型的FtsZ进行共聚。以前的研究主要基于模式植物物种的FtsZ蛋白，导致假设它们的共聚增强了Z环内的聚合物重排(动力学)，这是Z环收缩所必需的。这个项目的重点是更详细地了解FtsZ对如何不仅在植物中，而且在藻类中合作进行叶绿体分裂。实验方法将包括通过荧光成像分析酵母中重组的Z环的动力学，一套体外组装和生化分析，更好地了解FtsZ对在聚合物中如何相互作用的计算建模，以及研究两个FtsZ如何在聚合物中排列的先进显微镜技术。由于共聚是叶绿体特有的Z环功能的一种新的和重要的变异，对FtsZ对的研究将有助于更广泛地理解FtsZ介导的分裂系统的多样性。

Plants possess specialized compartments called chloroplasts that allow them to harvest light energy directly from the sun and convert it to chemical energy through the process of photosynthesis. Photosynthesis produces the organic compounds that comprise the base of the global food chain and are crucial for agricultural production. As plant cells expand during leaf growth, their chloroplast numbers increase dramatically through the process of division, which is crucial for increasing photosynthetic capacity. Consistent with their cyanobacterial origin, chloroplasts inherited several components of their division machinery from the cell division machinery in their prokaryotic ancestors. Foremost among these is a cytoskeletal protein called FtsZ. In both bacteria and chloroplasts, FtsZ proteins assemble into polymers that form a ring, called the "Z ring", at the center of the cell or organelle that contributes to the constrictive force driving the division process. This project seeks insight into how chloroplasts use these proteins in division and seeks a better understanding of the differences between chloroplast and prokaryotic division. Broader Impact activities will include participation in the Michigan State University Girl Scout STEM Demo Day, which provides hands-on demonstrations and activities to girls from across the state. Also, a post-doc will be involved in updating and expanding the Wikipedia page on chloroplast biology to help the general public better understand how chloroplasts work.Whereas bacterial cell division requires only a single type of FtsZ, chloroplast division requires two functionally distinct types of FtsZ that copolymerize. Previous studies based largely on the FtsZ proteins from a model plant species have led to the hypothesis that their copolymerization enhances polymer rearrangements (dynamics) within the Z ring, which is essential for Z-ring constriction. This project focuses on understanding in greater mechanistic detail how FtsZ pairs cooperate not only in plants, but also in algae, to carry out chloroplast division. Experimental approaches will include analysis of the dynamics of Z rings reconstituted in yeast by fluorescence imaging, a suite of in vitro assembly and biochemical assays, computational modeling to better understand how FtsZ pairs interact in polymers, and advanced microscopy techniques to investigate how the two FtsZs are arranged in polymers. As copolymerization represents a novel and important variation on Z-ring function unique to chloroplasts, study of FtsZ pairs will contribute to broader understanding of the diversity of FtsZ-mediated division systems.