2011-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/677948摘要：根瘤菌與豆科植物共生，形成根瘤而將大氣中的氮氣固定以供給植物利用。整個結瘤過程牽涉到植物與微生物間複雜的訊息交換。初期的根瘤形成與後期表達固氮作用的訊息傳導因子已經陸續被發現。相較於此，中期的根瘤成熟階段，也就是根瘤菌在植物細胞內經由分化作用形成類菌體（bacteroid）到表達共生固氮前所牽涉的分子訊息傳達機制至今依然不明。 本研究所採用的共生系統為Azorhizobium caulinodans 根瘤菌與其宿主 Sesbania rostrata。S. rostrata不僅在根毛上可產生根瘤，若將菌接種在側根(莖)上也可長出具固氮功能的莖瘤。由於莖瘤易於觀察，結瘤時期也一致，較利於做時序性的成熟過程追蹤實驗。根據我們先前的研究發現，Azorhizobium的染色體分配系統（ParA與 ParB 蛋白）除了參與染色體分配外，也在類菌體分化過程中扮演著負調控者的角色。 本研究將進一步利用系統生物學的工具，即結合分子生物學、生物化學、次世代定序分析、高通量蛋白質體學等分析方法探討Azorhizobium 根瘤菌的染色體分配系統如何精確地調控類菌體的形成時機。此外，我們也預期從S. rostrata 尋找來自宿主植物所分泌的訊息胜&#32957;，並瞭解這些物質是如何被根瘤菌辨識與其相關訊息傳導機制。 <br> Abstract: Symbiosis between legumes and rhizobia leads to the formation of nitrogen-fixing root nodules. The nodulation process is highly complex, involving a succession of interactions between the host plants and the microsymbionts. However, little is known about the molecular basis of events in nodule maturation process, i.e. after the bacteria are released from infection threads into the nodules and differentiating into bacteroid before nitrogen fixation begins. Azorhizobium caulinodans ORS571 is a microsymbiont of Sesbania rostrata. Nitrogen-fixing nodules are formed by A. caulinodans on the stems as well as on the roots of S. rostrata. This symbiotic system is a versatile tool for exploring the molecular mechanism of nodule formation and maintenance. Our experimental evidence has demonstrated that the azorhizobial chromosome partition proteins (ParA and ParB) not only played crucial roles in the partitioning of chromosome, but also negatively regulates the bacteroid formation process in S. rostrata stem nodules. In this study, we will use a systems biology approach, i.e. combination of molecular, biochemical, next generation sequencing, high-throughput proteomics analysis and bioinformatics tools to elucidate how the azorhizobial chromosome partition system initiates bacteroid formation process on the proper timing. We also expect to identify the specific plant signal peptides from S. rostrata, and understand how rhizobia perceive these signals and how they transduce symbiotic signals to downstream components.共生根瘤形成類菌體分化氮缺乏系統微生物學symbiosisnodulationbacteroid differentiationnitrogen deficiencysystems microbiology