A two-component system plays an important role in the root-colonizing ability of Pseudomonas fluorescens strain WCS365
A two-component system plays an important role in the root-colonizing ability of Pseudomonas fluorescens strain WCS365
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DOI：
10.1094/mpmi.1998.11.1.45
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发表时间：
1998-01-01
影响因子：
3.5
通讯作者：
Lugtenberg, BJJ
中科院分区：
文献类型：
--
作者：
Dekkers, LC;Bloemendaal, CJP;Lugtenberg, BJJ
我们描述了高效定殖荧光假单胞菌WCS365的新的Tn5lacZ定殖突变体PCL1210的特征，在突变株和亲本细胞的1：I混合接种马铃薯茎条后，突变株PCL1210对马铃薯根尖的定殖率至少减少了300-1000倍。同样，突变体在番茄、小麦和萝卜上的定殖也受到损害，这表明涉及的基因在荧光假单胞菌WCS365在多种植物上定殖的能力中发挥作用。发现一个3.1kb的DNA片段能够补充观察到的突变。Tn5lacZ插入附近区域的核苷酸序列显示三个开放阅读框(ORF)。确定了转录起始点。操纵子之前是整合宿主因子(IHF)结合位点的共识序列，而不存在明确的-10和-35序列。该操纵子的前两个基因的氨基酸序列命名为colr和cols，与已知的双组分调控系统成员有很强的相似性。ColR与OmpR-Phob亚类的反应调节子具有同源性，而突变所在基因的产物COLS与这些双组分系统的传感器激酶成员显示出相似性。疏水性图显示，这种假想的传感器激酶有两个跨膜区，这一点对其他传感器激酶也是已知的。第三个ORF的产物Orf222与已知的蛋白质没有同源性。Orf222基因只有一部分存在于定殖互补的3.1kb区域，因此它不起互补作用。没有实验证据表明Colr/COLS两组分系统在可疑的侵袭特性、趋化性和渗出物的运输中起作用。因此，这一新的双组分系统的功能仍有待阐明。我们的结论是，殖民是一个活跃的过程，在这个过程中，环境刺激通过这个两组分系统，激活了一种迄今未知的特征，这对殖民至关重要。
We describe the characterization of a novel Tn5lacZ colonization mutant of the efficiently colonizing Pseudomonas fluorescens strain WCS365, mutant strain PCL1210, which is at least 300- to 1,000-fold impaired in colonization of the potato root tip after co-inoculation of potato stem cuttings with a 1:I mixture of mutant and parental cells. Similarly, the mutant is also impaired in colonization of tomato, wheat, and radish, indicating that the gene involved plays a role in the ability of P. fluorescens WCS365 to colonize a wide range of plant species. A 3.1-kb DNA fragment was found to be able to complement the observed mutation. The nucleotide sequence of the region around the Tn5lacZ insertion showed three open reading frames (ORFs). The transcriptional start site was determined. The operon is preceded by an integration host factor (IHF) binding site consensus sequence whereas no clear -10 and -35 sequences are present. The deduced amino acid sequences of the first two genes of the operon, designated as colR and colS, show strong similarity with known members of two-component regulatory systems. ColR has homology with the response regulators of the OmpR-PhoB subclass whereas ColS, the product of the gene in which the mutation resides, shows similarity to the sensor kinase members of these two-component systems. Hydrophobicity plots show that this hypothetical sensor kinase has two transmembrane domains, as is also known for other sensor kinases. The product of the third ORF, Orf222, shows no homology with known proteins. Only part of the orf222 gene is present in the colonization-complementing, 3.1-kb region, and it therefore does not play a role in complementation. No experimental evidence for a role of the ColR/ColS two-component system in the suspected colonization traits chemotaxis and transport of exudate compounds could be obtained. The function of this novel two-component system therefore remains to be elucidated. We conclude that colonization is an active process in which an environmental stimulus, through this two-component system, activates a so far unknown trait that is crucial for colonization.