Analysis of a Bifunctional Plastid Nucleoid Protein: Ferrodoxin-Sulfite Reductase

叶绿体编码基因对植物生长和生产力的重要性是毋庸置疑的，然而令人惊讶的是，对细胞器的分子生物学和生物化学的许多方面，如叶绿体发育的控制和与此过程相关的信号的细胞内交流，人们知之甚少。对几种高等植物质体的测序提供了ctDNA编码的基因类型和数量的有价值的信息，并极大地增加了我们在转录和翻译水平上对细胞器基因调控的了解。另一方面，很可能对质体编码基因的表达产生深远影响的更高水平的结构决定因素基本上是未知的。由于质体体与蛋白质有关，这些蛋白质将多个基因组拷贝浓缩成紧凑的复合体，称为类核，因此必须进行类核的重排，才能进行转录、复制、重组和修复。虽然类核蛋白的组成随着叶绿体的发育而改变是已知的，但这些重塑事件的分子细节以及它们影响叶绿体核酸代谢的基本方面的方式(S)尚不清楚。本项目通过研究类质体核的一种主要结构蛋白的表达和与DNA的相互作用的调节来研究类核结构和功能的分子基础。通过遗传学、生物化学和细胞生物学相结合的方法，将评估DCP68/SIR与类质体核相关的生物学意义。DCP68/SIR是一种双功能的质体蛋白，在细胞器中具有类核成分和硫酸盐还原途径的双重作用，硫酸盐还原途径导致半胱氨酸和其他含硫代谢产物的生物合成。由于类核结构和功能的调节与硫的同化代谢有关这一有趣的可能性，本研究的结果将有助于理解植物细胞中控制细胞器发育和功能的分子过程和调控策略。这项研究将开始阐明类核结构在调控叶绿体基因表达和质体体传递和维持中的作用，从而有助于未来开发高效的质体组遗传操作策略。植物细胞的光合器官(叶绿体)含有自己的遗传物质(DNA)，编码许多对植物生长和生产力至关重要的产物。叶绿体DNA与蛋白质结合，这些蛋白质将其浓缩成所谓的类核，其结构和功能可能会在植物的生长和发育过程中发生变化。该项目探讨了叶绿体DNA压缩蛋白对细胞器DNA为复制和信息检索提供模板的能力的影响。这项研究的重点是叶绿体类核蛋白DCP68，它浓缩DNA，并在叶绿体中扮演额外的角色，将硫矿物质转化为植物可利用的形式。这项研究将研究环境和内部信号如何影响DCP68和叶绿体DNA之间的相互作用，并可能将类核结构和功能与细胞器的其他代谢方面联系起来。

The importance of chloroplast-encoded genes for plant growth and productivity is unquestionable, yet surprisingly, many aspects of molecular biology and biochemistry of the organelle, such as the control of chloroplast development and intracellular communication of signals related to this process are only poorly understood. The sequencing of several higher plant plastomes has provided valuable information of types and number of genes that are encoded by ctDNA and has greatly increased our knowledge of organellar gene regulation on the transcriptional and translational level. On the other hand, higher-level structural determinants that very likely have profound effects on the expression of plastome-encoded genes are essentially unknown. Since the plastome is associated with proteins that condense the multiple genome copies into compact complexes termed nucleoids, rearrangements of nucleoids must occur to allow transcription, replication, recombination and repair to take place. While nucleoid protein composition is known to change with plastid development, the molecular details of these remodeling events and the way(s) in which they affect the fundamental aspects of plastid nucleic acid metabolism are unknown. This project addresses the molecular basis of nucleoid structure and function by studying expression and regulation of interaction with DNA of a major structural protein of plastid nucleoids. Through a combined genetic, biochemical and cell biological approach, the biological significance of the association of DCP68/SiR with the plastid nucleoid will be assessed. DCP68/SiR appears to be a bifunctional plastid protein that fulfills dual roles in the organelle as a nucleoid constituent and an enzyme of the sulfate reduction pathway that leads to the biosynthesis of cysteine and other sulfur-containing metabolites. Because of the intriguing possibility that regulation of nucleoid structure and function is connected with that of the assimilatory sulfur metabolism, the results from this study will contribute to an understanding of the molecular processes and regulatory strategies in the plant cell that govern organellar development and function. The study will begin to elucidate the contribution of nucleoid structure in regulating plastid gene expression and plastome transmission and maintenance, and will thereby aid future efforts to develop efficient plastome genetic manipulation strategies.The photosynthetic organelles (chloroplasts) of plant cells contain their own genetic material (DNA) that encodes many products of great importance for plant growth and productivity. Chloroplast DNA is bound to proteins that condense it into so-called nucleoids whose structure and, presumably, function, change during plant growth and development. This project addresses the effects chloroplast DNA-compacting proteins have on the ability of the organelle's DNA to provide a template for duplication and for information retrieval. The study focuses on the chloroplast nucleoid protein DCP68, which condenses DNA and plays the additional role in the chloroplast of converting sulfur minerals to a form that is usable by the plant. The study will examine how environmental and internal signals affect the interaction between DCP68 and chloroplast DNA and might connect nucleoid structure and function with other metabolic aspects of the organelle.