2010-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/697366摘要：根瘤菌可與豆科植物共生，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被陸續發現。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。 在我們目前進行中的研究發現，當Azorhizobium 根瘤菌的染色體分配基因(parA ) 缺失的時候，除了會造成細胞染色體的不正常分配外，也會促使根瘤菌提早進行細胞分化，轉變成類菌體的形態。我們將此突變株接種到Sesbania rostrata 上，結瘤後所產生的莖瘤無論是大小或是固氮能力均劣於同時期接種的野生型莖瘤， 同時，在同ㄧ植株上可觀察到停滯在不同發育階段的莖瘤。我們根據實驗結果推測parA 基因除了參與染色體分配以外，也扮演了類菌體分化過程中的負調控者角色。這項根瘤菌的染色體分配基因參與調控根（莖）瘤成熟過程的發現是第一次被發表。 以上述研究成果作為基礎，本研究將進一步結合分子生物學、生物化學、細胞生物學、基因體學、蛋白質體學等分析方法探討Azorhizobium 根瘤菌的染色體分配系統（包括ParA與ParB蛋白）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 找出來自宿主植物的根瘤成熟訊息物質，並瞭解這些物質被根瘤菌辨識與訊息傳導的機制。 <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. In our on-going study, we have found that a null mutant of azorhizobial chromosome partition gene (parA) resulting in notable defects in chromosome partition. Besides, parA defected mutant had already been differentiated untimely before they invading the host plant. While Sesbania rostrata was inoculated with such mutant strain, immature stem-nodules were generated. The development of those aberrant stem-nodules was halted in diverse maturity stage. Our experimental evidence has demonstrated that parA gene not only played crucial roles in the partitioning of chromosome, but also negatively regulates the bacteroid formation process in S. rostrata stem nodules. This is the first report suggesting that rhizobial chromosome partition gene is involved in the nodulation of legumes. In this study, we will use a combination of molecular, biochemical, cell biology, genetic and proteomic approaches to elucidate how the azorhizobial chromosome partition system (including ParA and ParB proteins) initiates bacteroid formation process on the proper timing. We also expect to identify the specific plant signal molecules from S. rostrata, understand how rhizobia perceive these signals and how they transduce symbiotic signals to downstream components.共生固氮根瘤菌豆科Azorhizobium caulinodans田菁 Sesbania rostrata染色體分配根瘤成熟SymbiosisRhizobiumlegumeAzorhizobium caulinodansSesbania rostratachromosome partitionnodule maturation