McCarthy Yvonne, Ryan Robert P, O'Donovan Karen, He Yong-Qiang, Jiang Bo-Le, Feng Jia-Xun, Tang Ji-Liang, Dow J Maxwell
BIOMERIT Research Centre, Department of Microbiology, BioSciences Institute, National University of Ireland, Cork, Ireland.
Mol Plant Pathol. 2008 Nov;9(6):819-24. doi: 10.1111/j.1364-3703.2008.00495.x.
Cyclic di-GMP [(bis-(3'-5')-cyclic di-guanosine monophosphate)] is an almost ubiquitous second messenger in bacteria that is implicated in the regulation of a range of functions that include developmental transitions, aggregative behaviour, adhesion, biofilm formation and virulence. Comparatively little is known about the mechanism(s) by which cyclic di-GMP exerts these various regulatory effects. PilZ has been identified as a cyclic di-GMP binding protein domain; proteins with this domain are involved in regulation of specific cellular processes, including the virulence of animal pathogens. Here we have examined the role of PilZ domain proteins in virulence and the regulation of virulence factor synthesis in Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot of crucifers. The Xcc genome encodes four proteins (XC0965, XC2249, XC2317 and XC3221) that have a PilZ domain. Mutation of XC0965, XC2249 and XC3221 led to a significant reduction of virulence in Chinese radish. Mutation of XC2249 and XC3221 led to a reduction in motility whereas mutation of XC2249 and XC0965 affected extracellular enzyme production. All mutant strains were unaffected in biofilm formation in vitro. The reduction of virulence following mutation of XC3221 could not be wholly attributed to an effect on motility as mutation of pilA, which abolishes motility, has a lesser effect on virulence.
环二鸟苷酸[双（3'-5'）-环二鸟苷单磷酸]是细菌中一种几乎普遍存在的第二信使，参与调节一系列功能，包括发育转变、聚集行为、黏附、生物膜形成和毒力。关于环二鸟苷酸发挥这些各种调节作用的机制，人们了解得相对较少。PilZ已被鉴定为一种环二鸟苷酸结合蛋白结构域；具有该结构域的蛋白质参与特定细胞过程的调节，包括动物病原体的毒力。在这里，我们研究了PilZ结构域蛋白在野油菜黄单胞菌野油菜致病变种（Xcc，十字花科黑腐病的病原体）毒力及毒力因子合成调节中的作用。Xcc基因组编码四种具有PilZ结构域的蛋白质（XC0965、XC2249、XC2317和XC3221）。XC0965、XC2249和XC3221的突变导致在中国萝卜中毒力显著降低。XC2249和XC3221的突变导致运动性降低，而XC2249和XC0965的突变影响细胞外酶的产生。所有突变菌株在体外生物膜形成方面均未受影响。XC3221突变后毒力的降低不能完全归因于对运动性的影响，因为使运动性丧失的pilA突变对毒力的影响较小。
