Sinorhizobium medicae genes whose regulation involves the ActS and/or ActR signal transduction proteins

Fenner, Beau J.; Tiwari, Ravi; Reeve, Wayne; Dilworth, M. J.; Glenn, A. R.

doi:10.1016/j.femsle.2004.05.016

Cited by 10 publications

(5 citation statements)

References 67 publications

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“…Transcriptomic studies addressing the response of rhizobium to acidic pH and have revealed large networks regulating multiple genes in response to acidic pH ( Hellweg et al, 2009 ; Guerrero-Castro et al, 2018 ). The response of rhizobia to acidic pH is primarily regulated though two-component systems, actR/S and chvI / exoS / exoR ( Dilworth et al, 2000 ; Fenner et al, 2004 ). These systems ultimately control the regulation of cytoplasmic pH, or the production of and modification of extracellular elements for pH tolerance components ( Cunningham and Munns, 1984 ; Chen et al, 1993 ).…”

Section: Ph Stressmentioning

confidence: 99%

The Rhizobium-Legume Symbiosis: Co-opting Successful Stress Management

Hawkins

Oresnik

2022

Front. Plant Sci.

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The interaction of bacteria with plants can result in either a positive, negative, or neutral association. The rhizobium-legume interaction is a well-studied model system of a process that is considered a positive interaction. This process has evolved to require a complex signal exchange between the host and the symbiont. During this process, rhizobia are subject to several stresses, including low pH, oxidative stress, osmotic stress, as well as growth inhibiting plant peptides. A great deal of work has been carried out to characterize the bacterial response to these stresses. Many of the responses to stress are also observed to have key roles in symbiotic signaling. We propose that stress tolerance responses have been co-opted by the plant and bacterial partners to play a role in the complex signal exchange that occurs between rhizobia and legumes to establish functional symbiosis. This review will cover how rhizobia tolerate stresses, and how aspects of these tolerance mechanisms play a role in signal exchange between rhizobia and legumes.

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Section: Ph Stressmentioning

confidence: 99%

The Rhizobium-Legume Symbiosis: Co-opting Successful Stress Management

Hawkins

Oresnik

2022

Front. Plant Sci.

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“…On the basis of these and other previous results, the genetic analysis of acid tolerance in rhizobia in general, and in alfalfa symbionts in particular, emerged as a potential powerful approach for a rational improvement of the rhizobial performance at low pH. As a result of the screening of Tn 5 -mutant libraries, several genes for acid tolerance (namely act , among others) could be identified in S. medicae —including actA 30 and actR/S 31 32 , actP 33 , exoH 34 , and exoR 9 along with some other genes that were induced at low pH, such as phrR 35 and lpiA 36 37 . The collected genetic evidence indicates that tolerance to acidity in these rhizobia is a multigenic phenotype.…”

mentioning

confidence: 94%

A consolidated analysis of the physiologic and molecular responses induced under acid stress in the legume-symbiont model-soil bacterium Sinorhizobium meliloti

Draghi

Papa

Hellweg

et al. 2016

Sci Rep

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Abiotic stresses in general and extracellular acidity in particular disturb and limit nitrogen-fixing symbioses between rhizobia and their host legumes. Except for valuable molecular-biological studies on different rhizobia, no consolidated models have been formulated to describe the central physiologic changes that occur in acid-stressed bacteria. We present here an integrated analysis entailing the main cultural, metabolic, and molecular responses of the model bacterium Sinorhizobium meliloti growing under controlled acid stress in a chemostat. A stepwise extracellular acidification of the culture medium had indicated that S. meliloti stopped growing at ca. pH 6.0–6.1. Under such stress the rhizobia increased the O2 consumption per cell by more than 5-fold. This phenotype, together with an increase in the transcripts for several membrane cytochromes, entails a higher aerobic-respiration rate in the acid-stressed rhizobia. Multivariate analysis of global metabolome data served to unequivocally correlate specific-metabolite profiles with the extracellular pH, showing that at low pH the pentose-phosphate pathway exhibited increases in several transcripts, enzymes, and metabolites. Further analyses should be focused on the time course of the observed changes, its associated intracellular signaling, and on the comparison with the changes that operate during the sub lethal acid-adaptive response (ATR) in rhizobia.

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“…The encoded response regulator ActR is activated by its corresponding sensor histidine kinase ActS, whose loss also leads to sensitivity to low pH. The cbbS gene involved in CO 2 fixation and the narB gene involved in nitrate assimilation as well as the nitrogen fixation regulator genes fixK and nifA could be identified as target genes for the regulator ActR [23]. Along with the genes required for low pH tolerance some further genes up-regulated by low pH were identified for S. medicae [19,24].…”

Section: Introductionmentioning

confidence: 99%

The time course of the transcriptomic response of Sinorhizobium meliloti1021 following a shift to acidic pH

2009

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BackgroundThe symbiotic soil bacterium Sinorhizobium meliloti often has to face low pH in its natural habitats. To identify genes responding to pH stress a global transcriptional analysis of S. meliloti strain 1021 following a pH shift from pH 7.0 to pH 5.75 was carried out. In detail, oligo-based whole genome microarrays were used in a time course experiment. The monitoring period covered a time span of about one hour after the pH shift. The obtained microarray data was filtered and grouped by K-means clustering in order to obtain groups of genes behaving similarly concerning their expression levels throughout the time course.ResultsThe results display a versatile response of S. meliloti 1021 represented by distinct expression profiles of subsets of genes with functional relation. The eight generated clusters could be subdivided into a group of four clusters containing genes that were up-regulated and another group of four clusters containing genes that were down-regulated in response to the acidic pH shift. The respective mean expression progression of the four up-regulated clusters could be described as (i) permanently and strong, (ii) permanently and intermediate, (iii) permanently and progressive, and (iv) transiently up-regulated. The expression profile of the four down-regulated clusters could be characterized as (i) permanently, (ii) permanently and progressive, (iii) transiently, and (iv) ultra short down-regulated. Genes coding for proteins with functional relation were mostly cumulated in the same cluster, pointing to a characteristic expression profile for distinct cellular functions. Among the strongest up-regulated genes lpiA, degP1, cah, exoV and exoH were found. The most striking functional groups responding to the shift to acidic pH were genes of the exopolysaccharide I biosynthesis as well as flagellar and chemotaxis genes. While the genes of the exopolysaccharide I biosynthesis (exoY, exoQ, exoW, exoV, exoT, exoH, exoK exoL, exoO, exoN, exoP) were up-regulated, the expression level of the flagellar and chemotaxis genes (visR, motA, flgF, flgB, flgC, fliE, flgG, flgE, flgL, flbT, mcpU) simultaneously decreased in response to acidic pH. Other responding functional groups of genes mainly belonged to nitrogen uptake and metabolism (amtB, nrtB, nirB, nirD), methionine metabolism (metA, metF, metH, metK, bmt and ahcY) as well as ion transport systems (sitABCD, phoCD). It is noteworthy, that several genes coding for hypothetical proteins of unknown function could be identified as up-regulated in response to the pH shift.ConclusionIt was shown that the short term response to acidic pH stress does not result in a simple induction or repression of genes, but in a sequence of responses varying in their intensity over time. Obviously, the response to acidic pH is not based on a few specific genes, but involves whole sets of genes associated with various cellular functions.

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Sinorhizobium medicae genes whose regulation involves the ActS and/or ActR signal transduction proteins

Cited by 10 publications

References 67 publications

The Rhizobium-Legume Symbiosis: Co-opting Successful Stress Management

The Rhizobium-Legume Symbiosis: Co-opting Successful Stress Management

A consolidated analysis of the physiologic and molecular responses induced under acid stress in the legume-symbiont model-soil bacterium Sinorhizobium meliloti

The time course of the transcriptomic response of Sinorhizobium meliloti1021 following a shift to acidic pH

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