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標題: 阿拉伯芥RTNLB1-8蛋白質於農桿菌感染時之功能分析
Functional Characterization of Rtnlb1-8 Proteins in Agrobacterium-Mediated Plant Transformation Process
作者: 黃皓瑄
關鍵字: 基礎研究;VirB2;生物科學類;農桿菌;T 線毛;AtRab8B;RTNLB
農桿菌可成功地轉殖許多植物和其他的真核生物,包括真菌及人類細胞等。在自然感染的過程中,農桿菌會使植物傷口處產生冠癭狀腫瘤,這是因為菌體內Ti 質體(tumor-inducing plasmid) 上有一段轉移DNA(transfer-DNA,T-DNA)會被嵌入植物基因體中所導致。農桿菌是利用位在細胞膜上由11 個VirB (Virulence B)蛋白質和VirD4 蛋白質所組成的運輸蛋白質結構,及T 線毛(T-pilus)共同組成的第四型分泌系統,將T-DNA 和Vir 蛋白質傳遞至植物細胞中。T 線毛是由許多的輪狀VirB2 蛋白質所組成。目前已分離出可與VirB2 蛋白質結合之二類植物蛋白質,分別是RTNLB1、RTNLB2、RTNLB4 及AtRab8B 蛋白質。對於這三個RTNLB 蛋白質如何參與農桿菌感染之過程並不清楚。且至目前為止,仍未分離出許多可能參與幫助T-DNA 及Vir 蛋白質傳遞至植物細胞中的植物蛋白質。於此研究計畫中,我們將以遺傳學、細胞學及生化學的研究方法,進一步瞭解RTNLB1、RTNLB2 及RTNLB4 蛋白質是否可於植物細胞內形成蛋白質覆合體並可位於細胞表面,以幫助農桿菌轉移T-DNA及Vir 蛋白質。並且同時了解RTNLB蛋白質家族中之其他成員,是否也有參與農桿菌之感染過程。此研究結果將幫助我們鑑定出可能參與在T-DNA 及Vir 蛋白質傳遞過程中一些重要的植物蛋白質;並且幫助我們對RTNLB 蛋白質於農桿菌感染時,所扮演之角色有進一步的瞭解。

Agrobacterium tumefaciens causes crown gall disease on a wide variety of plants. Duringinfections, a defined region of a resident tumor-inducing (Ti) plasmid, T-DNA, is transferredfrom the bacterium to plants where it integrates into the plant genome. Agrobacterium uses aType IV secretion system (T4SS) to transfer T-DNA and Virulence proteins to plants. TheT4SS is composed of two major structural components: the T-pilus and a membraneassociated complex that is responsible for translocating substrates across both bacterialmembranes. VirB2 protein is the major component of the T-pilus. Two classes of plantproteins, RTNLB1 (Reticulon-Like B1), RTNLB2, RTNLB4 and a membrane-associatedGTPase, AtRab8B, interact with VirB2 in yeast and in vitro. Anti-sense and RNA interference(RNAi) transgenic plants of RTNLB1, 2, 4, and AtRab8B are more resistant to stable andtransient Agrobacterium transformation than are wild-type plants. Arabidopsis plants withT-DNA insertions in RTNLB1, RTNLB2, or RTNLB4 show reduced levels ofAgrobacterium-mediated root transformation. Over-expression of RTNLB1, RTNLB2, orRTNLB4 proteins in transgenic Arabidopsis results in plants that are hyper-susceptible toAgrobacterium-mediated transformation. These data suggest that three RTNLB proteins andAtRab8B are involved in the initial interaction of A. tumefaciens with plant cells. The detailedmechanism relating how the three RTNLB proteins participate in Agrobacterium-mediateplant transformation is not clear. Not many plant proteins have been implicated in the earlysteps of Agrobacterium-mediated transformation. We will utilize cell biology, biochemical,and genetic approaches to determine if these three RTNLB proteins can form a proteincomplex that is localized to the cell periphery to mediate T-DNA and Vir protein transfer. Wewill also determine if other members of the RTNLB protein family participate inAgrobacterium-mediated transformation. Further characterizations of RTNLB proteinfunctions will help us understand how these plant proteins are involved inAgrobacterium-mediated transformation process. The results from these studies may lead tothe discovery of novel important plant proteins that participate in the initial transformationstep of T-DNA and virulence protein transfer into plant cells.
其他識別: NSC100-2311-B005-002
Appears in Collections:生命科學系所

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