SUGARS INDUCE THE AGROBACTERIUM VIRULENCE GENES THROUGH A PERIPLASMIC BINDING-PROTEIN AND A TRANSMEMBRANE SIGNAL PROTEIN
SUGARS INDUCE THE AGROBACTERIUM VIRULENCE GENES THROUGH A PERIPLASMIC BINDING-PROTEIN AND A TRANSMEMBRANE SIGNAL PROTEIN
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DOI：
10.1073/pnas.87.17.6708
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发表时间：
1990-09-01
影响因子：
11.1
通讯作者：
NESTER, EW
中科院分区：
文献类型：
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作者：
CANGELOSI, GA;ANKENBAUER, RG;NESTER, EW
酚类植物代谢物如乙酰丁香酮通过跨膜病毒蛋白诱导农杆菌毒力（vir）基因转录。我们在这里报道，某些糖通过一种独特的调控途径（包括病毒a和染色体编码的毒力蛋白ChvE）与酚类诱导剂协同诱导vir基因。序列比较表明，ChvE是一种与放射农杆菌中分离的GBP1蛋白相对应的质周半乳糖结合蛋白。像大肠杆菌中的同源糖结合蛋白一样，ChvE对半乳糖和其他几种糖的趋化性是必需的。当乙酰丁香酮不存在或低浓度存在时，这些糖在野生型细胞中强烈诱导vir基因表达。chvE的突变消除了糖对vir基因的诱导，导致感染宿主范围有限，但不影响乙酰丁香酮对vir基因的诱导。缺乏VirA外质结构域的突变体表现出与chvE突变体相同的调节表型和有限的宿主范围。这些数据表明，vir基因受两种不同类型的植物源诱导剂通过不同的调控途径调控，这些途径可以通过突变分离。糖的诱导对某些但不是所有植物寄主的感染是必需的。
Phenolic plant metabolites such as acetosyringone induce transcription of the virulence (vir) genes of Agrobacterium tumefaciens through the transmembrane VirA protein. We report here that certain sugars induce the vir genes synergistically with phenolic inducers by way of a distinct regulatory pathway that includes VirA and a chromosomally encoded virulence protein, ChvE. Sequence comparison showed that ChvE is a periplasmic galactose-binding protein corresponding to the GBP1 protein isolated from Agrobacterium radiobacter. Like homologous sugar-binding proteins in Escherichia coli, ChvE was required for chemotaxis toward galactose and several other sugars. These sugars strongly induced vir gene expression in wild-type cells when acetosyringone was absent or present in low concentrations. Mutations in chvE abolished vir gene induction by sugars and resulted in a limited host range for infection but did not affected vir gene induction by acetosyringone. A mutant lacking the periplasmic domain of VirA exhibited the same regulatory phenotype and limited host range as chvE mutants. These data show that the vir genes are regulated by two separate classes of plant-derived inducers by way of distinct regulatory pathways that can be separated by mutation. Induction by sugars is essential for infection of some but not all plant hosts.