HarpinPss是Pseudomonas syringae pv. syringae的hrp基因群中的hrpZ製造出的致敏蛋白，是種富含甘胺酸、缺乏胱胺酸的蛋白，它由細菌第三型分泌系統送到植物細胞外，能在非寄主植物如菸草中引起過敏應(hypersensitive response, HR)。HRAP (hypersensitive response assisting protein)，是從被HarpinPss引起過敏反應的甜椒中純化出來的雙極性(amphipathic)蛋白。HarpinPss在中性溶液中會聚集成多聚體，而HRAP能使HarpinPss多聚體分離成單體或二聚體，引發較強的過敏反應。因此HRAP和HarpinPss的作用機制是值得探討的問題，而本實驗主要藉由剔除(truncated)HRAP序列中的帶正電荷區域，cAMP磷酸化區或訊號序列區,並和HarpinPss以各種組合搭配，找尋兩個蛋白之間交互作用的區域。結果發現，當HRAP的cAMP磷酸化區存在時，能和harpinPss交互作用並把抗病訊號藉由MAPK訊號路徑傳遞下去；若無HARP之cAMP磷酸化區，harpinPss則形成多聚體，嵌在植物細胞膜上，造成離子滲漏，進而啟動過敏反應。

HarpinPss, a proteinaceous elicitor from Pseudomonas syringae pv. syringae, is a glycine-rich, cysteine-lacking, heat-stable protein. It can elicit the hypersensitive response (HR) when delivered to the surface of plant cells. HRAP (hypersensitive response assisting protein) is an amphipathic protein purified from sweet pepper and could intensify harpinPss–mediated HR in sweet pepper. In the previous research, harpinPss was present as monomer, dimer, trimer, tetramer, and ocatamer forms in neutral pH buffer. Only monomer and dimer forms of harpinPss induced hypersensitive response in nonhost plants. HRAP could cause multimeric forms of harpinPss dissociation into monomer forms. The interaction between HRAP and harpinPss is an important issue. HRAP contained three positively charged regions, a typical signal peptide and a cAMP-dependent phosphorylation site. In this study, these regions of HRAP would be truncated and identified whether these truncated HRAP fragments could promote harpinPss dissociation. Different combinations of truncated HRAP and harpinPss were used to identify the protein-interaction regions between two proteins. HarpinPss triggers HR via interaction with cAMP phosphorated region of HRAP and MAPK pathway transduction. When cAMP region of HRAP was truncated, harpinPss still triggers HR via polymerization and anchor on lipid bilayers to form an ion-conducting pore.

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English Abstract --------------------------------------- II
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Materials and Methods ----------------------------------- 5
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Discussion --------------------------------------------- 14
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