The HD-GYP domain protein RpfG of Xanthomonas oryzae pv. oryzicola regulates synthesis of extracellular polysaccharides that contribute to biofilm formation and virulence on rice.
The HD-GYP domain protein RpfG of Xanthomonas oryzae pv. oryzicola regulates synthesis of extracellular polysaccharides that contribute to biofilm formation and virulence on rice.
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DOI：
10.1371/journal.pone.0059428
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Sun W
中科院分区：
文献类型：
--
作者：
Zhang Y;Wei C;Jiang W;Wang L;Li C;Wang Y;Dow JM;Sun W
细菌性条斑病。oryzicola（Xoc）是水稻上最重要的病害之一。然而，对Xoc的致病机制知之甚少。本文研究了三种HD-GYP结构域调控蛋白在Xoc生物膜形成、毒力因子合成和毒力中的作用。rpfG基因的缺失导致胞外多糖（EPS）的产生改变，消除了对水稻的毒性，增强了生物膜的形成，但对蛋白酶的分泌和运动性影响不大。相反，突变分析表明，其他两个HD-GYP结构域蛋白对毒力因子合成和测试表型没有影响。rpfG的突变导致III型分泌系统的上调和三个假定的糖基转移酶基因gumD、pgaC和xagB的表达改变，这三个基因是指导不同胞外多糖合成的操纵子的一部分。pgaABCD和xagABCD操纵子在Xoc ΔrpfG突变体中显著上调，而gum基因的表达没有改变或略有增强。在缺失gumD、xagA和xagB后，Xoc ΔrpfG突变体的生物膜形成显著降低，但在缺失pgaA和pgaC后则没有。有趣的是，在这些单基因突变体中，只有ΔgumD突变体表现出多种表型改变，包括生物膜和EPS产生减少以及对水稻的毒性减弱。这些数据表明，RpfG是一个全球性的调节器，控制生物膜形成，EPS生产和细菌毒力在Xoc和gumD和xagB依赖性EPS有助于在不同条件下的生物膜形成。
Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most important diseases in rice. However, little is known about the pathogenicity mechanisms of Xoc. Here we have investigated the function of three HD-GYP domain regulatory proteins in biofilm formation, the synthesis of virulence factors and virulence of Xoc. Deletion of rpfG resulted in altered production of extracellular polysaccharides (EPS), abolished virulence on rice and enhanced biofilm formation, but had little effect on the secretion of proteases and motility. In contrast, mutational analysis showed that the other two HD-GYP domain proteins had no effect on virulence factor synthesis and tested phenotypes. Mutation of rpfG led to up-regulation of the type III secretion system and altered expression of three putative glycosyltransferase genes gumD, pgaC and xagB, which are part of operons directing the synthesis of different extracellular polysaccharides. The pgaABCD and xagABCD operons were greatly up-regulated in the Xoc ΔrpfG mutant, whereas the expression of the gum genes was unaltered or slightly enhanced. The elevated biofilm formation of the Xoc ΔrpfG mutant was dramatically reduced upon deletion of gumD, xagA and xagB, but not when pgaA and pgaC were deleted. Interestingly, only the ΔgumD mutant, among these single gene mutants, exhibits multiple phenotype alterations including reduced biofilm and EPS production and attenuated virulence on rice. These data indicate that RpfG is a global regulator that controls biofilm formation, EPS production and bacterial virulence in Xoc and that both gumD- and xagB-dependent EPS contribute to biofilm formation under different conditions.
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