The PhyR‐σ<sup>EcfG</sup> signalling cascade is involved in stress response and symbiotic efficiency in <i>Bradyrhizobium japonicum</i>

Gourion, Benjamin; Sulser, Sandra; Frunzke, Julia; Francez‐Charlot, Anne; Stiefel, Philipp; Pessi, Gabriella; Vorholt, Julia A.; Fischer, Hans‐Martin

doi:10.1111/j.1365-2958.2009.06769.x

Cited by 107 publications

(144 citation statements)

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“…Consistent with this finding, the hpnP gene in R. palustris TIE-1 is regulated by an extracytoplasmic function transcription factor conserved in alphaproteobacteria that has a role in establishing plant symbioses in Bradyrhizobium japonicum and Methylobacterium extorquens (Gourion et al, 2006(Gourion et al, , 2009. This factor induces hpnP expression in response to osmotic stress in R. palustris (Kulkarni et al, 2013); osmolyte production by plants in the rhizosphere is well documented, and in some cases has been shown to promote plant-microbe symbioses (Miller and Wood, 1996;Khamar et al, 2010).…”

Section: -Mebhp Production Is Niche Specific Jn Ricci Et Alsupporting

confidence: 64%

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

et al. 2013

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Molecular fossils of 2-methylhopanoids are prominent biomarkers in modern and ancient sediments that have been used as proxies for cyanobacteria and their main metabolism, oxygenic photosynthesis. However, substantial culture and genomic-based evidence now indicates that organisms other than cyanobacteria can make 2-methylhopanoids. Because few data directly address which organisms produce 2-methylhopanoids in the environment, we used metagenomic and clone library methods to determine the environmental diversity of hpnP, the gene encoding the C-2 hopanoid methylase. Here we show that hpnP copies from alphaproteobacteria and as yet uncultured organisms are found in diverse modern environments, including some modern habitats representative of those preserved in the rock record. In contrast, cyanobacterial hpnP genes are rarer and tend to be localized to specific habitats. To move beyond understanding the taxonomic distribution of environmental 2-methylhopanoid producers, we asked whether hpnP presence might track with particular variables. We found hpnP to be significantly correlated with organisms, metabolisms and environments known to support plant-microbe interactions (P-valueo10 À 6 ); in addition, we observed diverse hpnP types in closely packed microbial communities from other environments, including stromatolites, hot springs and hypersaline microbial mats. The common features of these niches indicate that 2-methylhopanoids are enriched in sessile microbial communities inhabiting environments low in oxygen and fixed nitrogen with high osmolarity. Our results support the earlier conclusion that 2-methylhopanoids are not reliable biomarkers for cyanobacteria or any other taxonomic group, and raise the new hypothesis that, instead, they are indicators of a specific environmental niche.

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Section: -Mebhp Production Is Niche Specific Jn Ricci Et Alsupporting

confidence: 64%

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

et al. 2013

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“…The homologue of B. melitensis RpoE1 in Bradyrhizobium japonicum genome is s EcfG (Gourion et al, 2009 Table S1, available with the online version of this paper). Among them, the presence of rpoE1 suggests an autoregulation, as described in Escherichia coli and other bacteria (Rhodius et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

RpoE1, an extracytoplasmic function sigma factor, is a repressor of the flagellar system in Brucella melitensis

et al. 2011

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RpoE1, an extracytoplasmic function sigma factor, is a repressor of the flagellar system in Brucella melitensis Unité de Recherche en Biologie Molé culaire (URBM), Faculté s Universitaires Notre-Dame de la Paix Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur, BelgiumThe genome of Brucella melitensis contains genes coding for the sigma factors RpoD, RpoN, RpoH1, RpoH2, RpoE1 and RpoE2. Previously published data show that B. melitensis is flagellated and that an rpoE1 mutant overexpresses the flagellar protein FlgE. In this study, we demonstrate that mutation of rpoE1 causes an overexpression of the flagellar genes fliF, flgE, fliC, flaF and flbT, correlating with the production of a longer filament and thereby demonstrating that RpoE1 acts as a flagellar repressor. Moreover, mutation of rpoE1 increases the promoter activity of the flagellar master regulator ftcR, suggesting that RpoE1 acts upstream of ftcR. Together, these data show that RpoE1 represses the flagellar synthesis and filament length in B. melitensis. INTRODUCTIONBrucellae are Gram-negative, intracellular pathogenic bacteria that cause brucellosis in a variety of mammals, including humans. For a long time, they were considered as being unflagellated. However, a sheathed flagellum has recently been discovered in Brucella melitensis and flagellar mutants are found to be impaired for infection in vivo (Ferooz & Letesson, 2010;Fretin et al., 2005;Zygmunt et al., 2006).The bacterial flagellum is a complex organelle used for motility and consists of at least three structural elements, the basal body, the hook and the filament (Macnab, 1999). The basal body, working as a motor, is embedded within the cell envelope and is anchored in the cytoplasmic membrane via the MS-ring structure, while the hook and filament, which function as a universal joint and a propeller, respectively, extend outwards from the cells (Minamino et al., 2008).Sigma and anti-sigma factors play important roles in the regulation of the flagellar genes (Smith & Hoover, 2009). The genome of B. melitensis has revealed the presence of genes encoding six sigma factors (rpoD, rpoH1, rpoH2, rpoE1, rpoE2 and rpoN) (Delory et al., 2006). The rpoD gene encodes the housekeeping sigma factor, the rpoH1 and rpoH2 genes encode two s 32 homologues, rpoE1 and rpoE2 encode two extracytoplasmic function (ECF) sigma factors and the rpoN gene encodes a s 54 homologue. The phenotypic characterizations were done on the five nonessential sigma factor mutants DrpoH1, DrpoH2, DrpoE1, DrpoE2 and DrpoN (Delory et al., 2006). Interestingly, at early growth phase in rich liquid medium, DrpoE1 overproduces the flagellar hook protein FlgE, suggesting that the flagellar system synthesis could be downregulated by the ECF sigma factor RpoE1 in B. melitensis (Delory et al., 2006).In this study, we demonstrate that the ECF sigma factor RpoE1 is a flagellar repressor in B. melitensis and that RpoE1 controls the length of the flagellar filament. METHODSBacterial strains and culture conditions. All strains and plasmids used ...

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“…Because PhyR uses a degenerate N-terminal sigma factor-like output domain to compete with σ EcfG for NepR binding, this partner switch was coined "sigma factor mimicry" (1). The importance of the alphaproteobacterial GSR in natural environments is underlined by several studies demonstrating its requirement for survival and competitiveness in the phyllosphere in Sphingomonas melonis (10) and Methylobacterium extorquens (8), the establishment of symbiotic interactions in Bradyrhizobium japonicum (9), and host-pathogen interactions in Brucella (6,11) and Bartonella (3) species.…”

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confidence: 99%

“…In Alphaproteobacteria, the GSR is controlled by an alternative extracytoplasmic function (ECF) sigma factor, usually called σ EcfG (1) or ECF15 sigma factor (2), the activity of which is regulated by a conserved partner-switching mechanism (1,(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). In unstressed conditions, σ EcfG is sequestered by its anti-sigma factor NepR.…”

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confidence: 99%

Complex two-component signaling regulates the general stress response in Alphaproteobacteria

Kaczmarczyk¹,

Hochstrasser²,

Vorholt³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Significance Bacteria possess many regulatory systems to monitor their environment and adapt their physiology accordingly. Whereas most systems sense one specific signal, the general stress response (GSR) is activated by many signals and protects cells against a wide range of adverse conditions. In Alphaproteobacteria, the GSR is controlled by the response regulator PhyR, but little is known about the upstream pathways. Here, we establish the GSR as a complex regulatory network composed of a particular family of partially redundant sensor kinases and of additional response regulators that modulate PhyR activity in Sphingomonas melonis . Given the broad conservation of this kinase family, it is possible that it plays a general role in the GSR in Alphaproteobacteria.

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The PhyR‐σ^EcfG signalling cascade is involved in stress response and symbiotic efficiency in Bradyrhizobium japonicum

Cited by 107 publications

References 48 publications

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

RpoE1, an extracytoplasmic function sigma factor, is a repressor of the flagellar system in Brucella melitensis

Complex two-component signaling regulates the general stress response in Alphaproteobacteria

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The PhyR‐σEcfG signalling cascade is involved in stress response and symbiotic efficiency in Bradyrhizobium japonicum

Cited by 107 publications

References 48 publications

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche

RpoE1, an extracytoplasmic function sigma factor, is a repressor of the flagellar system in Brucella melitensis

Complex two-component signaling regulates the general stress response in Alphaproteobacteria

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The PhyR‐σ^EcfG signalling cascade is involved in stress response and symbiotic efficiency in Bradyrhizobium japonicum