XerR, a negative regulator of XccR in Xanthomonas campestris pv. campestris, relieves its repressor function in planta  

作　　者：Li Wang Lili Zhang Yunfeng Geng Wei Xi Rongxiang Fang Yantao Jia 

机构地区：[1]State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, No. 3 Yard 1 West Beich enRoad, Chaoyang District, Beo'ing 100101, Chin~ [2]National Plant Gene Research Center, Beijing 100101, China [3]Graduate School of the Chinese Academy of Sciences, Beijing 100049, China [4]Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06510, USA [5]Temasek Life Sciences Laboratory, 1 Research Link, The National University of Singapore, Singapore 117604, Singapore

出　　处：《Cell Research》2011年第7期1131-1142,共12页细胞研究（英文版）

基　　金：supported by grants from the National Natural Science Foundation of China （No 31030008 and No 30471135）, and the National Basic Research Program of China （2011CB 100700）.

摘　　要：We previously reported that XccR, a LuxR-type regulator of Xanthomonas campestris pv. campestris （Xcc）, activates the downstream proline iminopeptidase virulence gene （pip） in response to certain host plant factor（s）. In this report, we further show that the expression of the xccR gene was repressed in the culture medium by an NtrC- type response regulator, which we named XerR （XccR expression-related, repressor）, and that this repression was relieved when the bacteria were grown in planta. Such a regulatory mechanism is reinforced by the observations that XerR directly bound to the xccR promoter in vitro, and that mutations at the phgsphorylation-related residues of XerR resulted in the loss of its repressor function. Furthermore, the expression level of xccR increased even in XerR- overexpressing Xcc cells when they were vacuum infiltrated into cabbage plants. We also preliminarily characterized the host factor（s） involved in the above mentioned interactions between Xcc and the host plant, showing that a plant material（s） with molecular weight（s） less than 1 kDa abolished the binding of XerR to the xccR promoter, while the same material enhanced the binding of XccR to the luxXc box in the pip promoter. Taken together, our results implicate XerR in a new layer of the regulatory mechanism controlling the expression of the virulence-related xccR/pip locus and provide clues to the identification of plant signal molecules that interact with XerR and XccR to enhance the virulence of Xcc.

关 键 词：Xcc NtrC-like regulator LuxR-like regulator proline iminopeptidase pathogen-host interaction plant signal（s） 

分 类 号：S435.111.4[农业科学—农业昆虫与害虫防治] TV146[农业科学—植物保护]