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National Chung Hsing University Institutional Repository - NCHUIR > 生命科學院 > 生物化學研究所 > 依資料類型分類 > 碩博士論文 >  調控植物免疫反應的負向因子HFR1是十字花科黑腐病菌第三型致病性蛋白XopD8004的植物標的蛋白

Please use this identifier to cite or link to this item: http://nchuir.lib.nchu.edu.tw/handle/309270000/152345

標題: 調控植物免疫反應的負向因子HFR1是十字花科黑腐病菌第三型致病性蛋白XopD8004的植物標的蛋白
HFR1, a negative regulator of plant immune response, was targeted by Xanthomonas. campestris pv. campestris type III effector XopD8004
作者: 陳俊銘
Tan, ChoonMeng
Contributors: 楊俊逸
生物化學研究所
關鍵字: 十字花科黑腐病菌;第三型致病性蛋白
Xanthomonas campestris pv. campestris;type III effectors
日期: 2012
Issue Date: 2013-11-07 13:21:40 (UTC+8)
Publisher: 生物化學研究所
摘要: Xanthomonas campestris pv. campestris (Xcc)為革蘭氏陰性植物病原菌,可藉由植物葉緣水孔和氣孔感染許多十字花科農作物,包括高麗菜、花椰菜和甘藍等,造成葉子出現潰瘍及黑色腐爛的病徵,俗稱黑腐病,同時此菌也可以感染模式植物擬南芥。Xcc藉由第三型分泌系統將第三型致病性蛋白注入到植物細胞中,調控宿主細胞的生理反應或干擾免疫系統來促進病原菌的繁殖。目前藉由分子遺傳實驗和生物資訊分析發現,Xcc含有超過25種第三型致病性蛋白分子,但是絕大多數第三型致病性蛋白的致病機制,目前尚未知。本研究利用已建構的Xcc8004第三型致病性蛋白分子轉殖植物進行探討,一方面排除致病性蛋白分子結構模仿和功能性重疊的特性,同時簡化第三型致病性蛋白的研究過程。實驗室先前發現致病性蛋白XopD8004的轉植株有胚軸延長的白化苗外表型,這和光型態發育的缺失有相關。本實驗利用酵母菌雙雜合系統發現XopD8004可以和光訊息傳導的轉錄因子HFR1進行結合。推測光訊息傳導也參與植物的免疫反應。為了瞭解HFR1和植物防禦系統的關係,利用hfr1突變株進行植物荷爾蒙水楊酸(SA)、茉莉酸(JA)和細菌鞭毛胜肽(Flg22)的處理,在qRT-PCR分析下得知hfr1突變株的生物逆境基因表現如:PR1、WRKY70、LOX2、PDF1.2等相對於野生型植株都有明顯的增加。同時在XopD8004轉植株中發現,XopD8004可以誘導和水楊酸有關的免疫基因表現,進而啟動免疫反應,因此推測HFR1在植物體內可能扮演誘餌的角色,讓XopD8004誤認HFR1為標的蛋白,進而引起植物的免疫反應來抵抗病原菌的入侵。
Xanthomonas campestris pv. campestris (Xcc) can infect a wide variety of species including cabbage, broccoli, cauliflower and the model plant Arabidopsis thaliana. The major pathogenicity system of Xcc is type III secretion system, which can inject type III effectors into host cell and interfere with the physiological responses of plant to suppress host immunity and promote the growth of pathogen. Based on molecular experiments and bioinformatic analyses, more than 25 effectors have been identified in Xcc. However, the machanisms of inhibiting the defense system of the plant by these effector are still remain unknown. To get a better understanding of the pathogenesis mechanism of Xcc type III effectors, Arabidopsis transgenic approach was used to overcome the problems of functional redundancy and structural mimics. Here, we provide direct evidence for the target of Xcc type III effector XopD8004. Using yeast two hybrid system, we found that XopD8004 interacts with Arabidopsis transcription factor HFR1, an important component involved in light signaling transduction pathway. The interaction between XopD8004 and HFR1 supports the phenomenon that overexpression of XopD8004 results in an etiolated phenotype with long hypocotyls, and it suggests that light signaling pathway crosstalks with plant immune system. Consistent with the hypothesis, the hfr1-201 mutant showed higher expression levels of defense response genes after salicylic acid (SA), jasmonic acid (JA) or flagellin 22 (Flg22) treatment and displayed resistance phenotypes against Xanthomonas. This phenomenon was also seen in XVE::XopD8004 transgenic plants after induction with β-estradiol. As a result, we proposed a “decoy model” that HFR1 acts as a target of XopD8004. The modified HFR1 subsequently triggers host defense response which is important to defend the infection of Xanthomonas.
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