- 學位論文
阿拉伯芥白胺酸重覆受體激酶IOS1與模式識別受體激酶FLS2及EFR結合並參與誘發先天性免疫作用
The Arabidopsis Malectin-Like/Leucine-Rich Repeat Receptor-Like Kinase IOS1 Associates with the Pattern Recognition Receptors FLS2 and EFR and is Critical for Priming of Pattern-Triggered Immunity
摘要
膜結合模式識別受體(PRR)例如鞭毛接收器(FLS2)和延伸因子接受器(EFR)，一旦辨識到微生物相關分子(Microbe-Associated Molecular Patterns; MAMP)即誘發先天性免疫作用(Pattern-Triggered Immunity; PTI)。本研究利用誘發劑BABA處理阿拉伯芥並藉由基因微陣列方法指出減弱卵菌敏感性1(IMPAIRED OOMYCETE SUSCEPTIBILITY1,IOS1)扮演一個誘發先天性免疫作用的關鍵角色。阿拉伯芥ios1突變株高度敏感於細菌性斑點病原菌(Pseudomonas syringae)。另外，研究證明ios1突變株在誘發先天性免疫作用產生缺陷,值得注意的是，突變株經由細菌或是微生物相關分子處理後會延遲誘發先天性免疫作用相關基因的表現,降低癒傷葡聚醣(callose)的沉澱並減弱絲裂原活化蛋白激酶mitogen-activated protein kinase (MAPK)的活性。反之，IOS1大量表現轉植株表現更抗細菌性斑點病原菌，並誘發更強的先天性免疫表現。另外，藉由胞外免疫沉澱法(pull-down)、雙分子螢光互補分析(BiFC)、共免疫沉澱法(Co-IP)及質譜分析(mass spectrometry analysis)結果證明IOS1與FLS2、EFR形成複合體。然而，IOS1也證實與油菜素內酯INSENSITIVE 1受體相關激酶1 (BRI1-Associated Kinase 1; BAK1)相互結合，並在微生物相關分子處理後正調控FLS2-BAK1結合。最後，IOS1突變株在BABA所誘發防禦過程中產生缺陷。整個研究顯示IOS1為一個新的調節蛋白參予在FLS2及EFR所首的訊息傳遞中並且在病菌攻擊時快速誘發先天性免疫反應。
並列摘要
Plasma membrane-localized pattern recognition receptors (PRRs) such as FLAGELLIN SENSING2 (FLS2) and EF-TU RECEPTOR (EFR) recognize microbe-associated molecular patterns (MAMPs) to activate the first layer of plant immunity termed pattern-triggered immunity (PTI). A reverse genetics approach with genes responsive to the priming agent beta-aminobutyric acid (BABA) revealed IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as a critical PTI player. Arabidopsis thaliana ios1 mutants were hyper-susceptible to Pseudomonas syringae bacteria. Accordingly, ios1 mutants demonstrated defective PTI responses, notably delayed up-regulation of PTI-marker genes, lower callose deposition and mitogen-activated protein kinase activities upon bacterial infection or MAMP treatment. Moreover, Arabidopsis lines over-expressing IOS1 were more resistant to P. syringae and demonstrated a primed PTI response. In vitro pull-down, bimolecular fluorescence complementation, co-immunoprecipitation and mass spectrometry analyses supported the existence of complexes between the membrane-localized IOS1 and FLS2, and EFR. IOS1 also associated with BRASSINOSTEROID INSENSITIVE1-ASSOCIATED KINASE1 (BAK1) in a ligand-independent manner, and positively regulated FLS2-BAK1 complex formation upon MAMP treatment. Finally, ios1 mutants were defective in BABA-induced resistance and priming. This work reveals IOS1 as a novel regulatory protein of FLS2- and EFR-mediated signaling that primes PTI activation upon bacterial elicitation.