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

叶绿体编码的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，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通信，仅知之甚少。 几种高等植物质体的测序提供了ctDNA编码的基因的类型和数量的有价值的信息，并大大增加了我们在转录和翻译水平上的细胞器基因调控的知识。 另一方面，很可能对质体编码基因的表达有深远影响的更高水平的结构决定因素基本上是未知的。 由于质体与将多个基因组拷贝浓缩成称为类核的紧凑复合物的蛋白质相关，因此必须发生类核的重排以允许转录、复制、重组和修复发生。 虽然已知类核蛋白组成随质体发育而变化，但这些重塑事件的分子细节以及它们影响质体核酸代谢的基本方面的方式是未知的。 本研究通过研究质体类核的主要结构蛋白质的表达及其与DNA相互作用的调控，探讨类核结构和功能的分子基础。 通过组合的遗传学、生物化学和细胞生物学方法，将评估DCP 68/SiR与质体类核的关联的生物学意义。 DCP 68/SiR似乎是一种双功能质体蛋白，其在细胞器中作为类核成分和硫酸盐还原途径的酶发挥双重作用，该途径导致半胱氨酸和其他含硫代谢物的生物合成。 由于类核结构和功能的调节与同化硫代谢有关的可能性，这项研究的结果将有助于了解植物细胞中控制细胞器发育和功能的分子过程和调节策略。 这项研究将开始阐明类核结构在调节质体基因表达和质体组传递和维持中的作用，从而有助于今后发展有效的质体组遗传操作策略。植物细胞的光合细胞器（叶绿体）含有它们自己的遗传物质（DNA），这些DNA编码许多对植物生长和生产力非常重要的产物。 叶绿体DNA与蛋白质结合，蛋白质将其浓缩成所谓的类核，类核的结构和功能在植物生长和发育过程中发生变化。 本计画探讨叶绿体DNA压缩蛋白质对细胞器DNA提供复制及资讯撷取模板的能力。 这项研究的重点是叶绿体类核蛋白DCP 68，它浓缩DNA，并在叶绿体中发挥额外的作用，将硫矿物质转化为植物可用的形式。 该研究将研究环境和内部信号如何影响DCP 68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.