Collaborative Research: Role of SCY2, a New Envelope Localized Translocase, in Plastid Biogenesis

地球上的大部分能量最终来自太阳，植物的叶绿体是至关重要的细胞器，因为它们允许植物捕获太阳能，并通过光合作用将这种能量转化为糖。在叶绿体中执行这些重要任务的大多数蛋白质都是在植物细胞的细胞质中合成的，被吸收到叶绿体间质室中，然后必须通过转座酶（一种将蛋白质转运到膜双层中的酶）特异性地靶向五个额外的叶绿体室中的一个。关于这种复杂的蛋白质定位网络，一个悬而未决的核心问题是：哪些系统负责转位酶蛋白质的靶向和整合？最近发现了一种位于叶绿体内包膜的Sec转位酶。破坏这种转位酶的突变会导致死亡，这表明它在叶绿体功能中起着至关重要的作用。初步结果表明，这个被命名为Sec2的系统是主转座酶，负责将所有其他转座酶蛋白放置到正确的叶绿体室中。Sec2将通过这个项目进一步表征。具体目标包括鉴定该系统的所有组成部分，表征Sec2靶向和易位/整合的蛋白质，以及建立一个检测系统来研究该易位系统对能量、辅助因子和靶向信息的需求。这项研究的成功完成将导致对这种新型转座酶在叶绿体生物发生中可能发挥的关键作用的深入了解。更广泛的影响本项目将为本科生、研究生和研究生水平的年轻科学家提供遗传学和生物化学交叉培训的机会。项目人员还将通过指导本科生实践研究经验，学习宝贵的教学和指导技能。在这个项目中将产生的植物品系将成为有价值的研究工具，并将分发给对叶绿体感兴趣的其他实验室。最后，由于许多重要的代谢和生物合成功能，包括光合作用和脂肪酸、必需氨基酸和维生素的合成，都集中在叶绿体中，因此当人们寻求修改、优化或以其他方式控制这些能力时，这项工作可能具有实际应用价值。

INTELLECTUAL MERITMost of the energy on earth comes ultimately from the sun, and plant chloroplasts are critical cellular organelles because they allow plants to capture solar energy and convert this energy to sugars through the process of photosynthesis. Most of the proteins that perform these important tasks in chloroplasts are synthesized in the cytosol of the plant cell, are taken up into the chloroplast stromal compartment, and then have to be specifically targeted to one of five additional chloroplast compartments by translocases, enzymes that transport proteins across or into membrane bilayers. A central unanswered question regarding this intricate protein localization network is: What system(s) are responsible for targeting and integration of the translocase proteins? A Sec translocase was recently discovered that is localized to the inner envelope of the chloroplast. Mutations that disrupt this translocase result in death, suggesting a critically important role in chloroplast function. Preliminary results suggest that this system, designated Sec2, is the master translocase, responsible for the placement of all other translocase proteins into their correct chloroplast compartment. Sec2 will be further characterized through this project. Specific aims include identification of all the components of the system, characterization of the proteins targeted and translocated/integrated by Sec2, and the establishment of an assay system to investigate the requirements for energy, accessory factors, and targeting information for this translocase system. Successful completion of the research will result in increased insight into the pivotal role that this novel translocase may play in the biogenesis of the chloroplast. BROADER IMPACTSThis project will provide cross-training opportunities in genetics and biochemistry for young scientists at the undergraduate, graduate, and postgraduate level. Project personnel will also learn valuable teaching and mentoring skills by supervising undergraduate students in hands-on research experiences. The plant lines that will be generated in this project will be valuable research tools and will be distributed to other laboratories interested in chloroplasts. Finally, because many vital metabolic and biosynthetic functions, including photosynthesis and synthesis of fatty acids, essential amino acids and vitamins, are centered in chloroplasts, the work may have practical applications as people seek to modify, optimize, or otherwise control these capacities.