The
            <i>katA</i>
            Catalase Gene Is Regulated by OxyR in both Free-Living and Symbiotic
            <i>Sinorhizobium meliloti</i>

Jamet, Alexandre; Kiss, Ernö; Batut, Jacques; Puppo, Alain; Hérouart, Didier

doi:10.1128/jb.187.1.376-381.2005

Cited by 36 publications

(44 citation statements)

References 40 publications

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“…In silico sequence analysis performed by us indicated that R. leguminosarum strains usually contain one housekeeping chromosomal gene and one to two genes located on plasmids that encode catalases. Jamet et al (2003Jamet et al ( , 2005 have indicated that S. meliloti possesses three distinct catalases: two monofunctional KatA and KatC enzymes and one bifunctional catalase-peroxydase KatB. The katB gene is constitutively expressed during bacterial growth in the culture and is not expressed under oxidative stress conditions, whereas the expression of the katA and katC genes was induced in these conditions.…”

Section: Discussionmentioning

confidence: 99%

The response of the Rhizobium leguminosarum bv. trifolii wild-type and exopolysaccharide-deficient mutants to oxidative stress

et al. 2013

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Aims The aim of this study was investigation of the response of R. leguminosarum bv. trifolii wild-type and its two rosR and pssA mutant strains impaired in exopolysaccharide (EPS) synthesis to oxidative stress conditions caused by two prooxidants: a superoxide anion generator-menadione (MQ) and hydrogen peroxide (H 2 O 2 ). Methods The levels of enzymatic (catalase, superoxide dismutase, pectinase and β-glucosidase) and nonenzymatic (superoxide anion generator, formaldehyde, phenolic compounds) biomarkers were monitored using biochemical methods in both the supernatants and rhizobial cells after treatment with 0.3mM MQ and 1.5mM H 2 O 2 . The viability of bacterial cells was estimated using fluorescent dyes and confocal laser scanning microscopy. In addition, the effect of prooxidants on symbiosis of the R. leguminosarum bv. trifolii strains with clover was established. Results The tested stress factors significantly changed enzymatic patterns of the rhizobial strains, and the wildtype strain proved to be more resistant to these prooxidants than both pssA and rosR mutants. Significantly higher activities of both catalase and superoxide dismutase have been detected in these mutants in comparison to the wildtype strain. H 2 O 2 and MQ also increased the levels of pectinase and β-glucosidase activities in the tested strains. Moreover, pre-incubation of R. leguminosarum bv. trifolii strains with the prooxidants negatively affected the viability of bacterial cells and the number of nodules elicited on clover plants. Conclusions EPS produced in large amounts by R. leguminosarum bv. trifolii plays a significant protective role as a barrier against oxidative stress factors and during symbiotic interactions with clover plants.

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Section: Discussionmentioning

confidence: 99%

The response of the Rhizobium leguminosarum bv. trifolii wild-type and exopolysaccharide-deficient mutants to oxidative stress

et al. 2013

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“…Most notably, KatA activity is upregulated in the sitA:mTn5 mutant. KatA is controlled by the global sensor of H 2 O 2 stress, OxyR (27). Upregulation of KatA suggests that even during normal growth, the sitA::mTn5 mutant experiences an increased intracellular stress from reactive oxygen species.…”

Section: Resultsmentioning

confidence: 99%

“…Several genes known to be required for defense against ROS in the free-living state are dispensable for symbiosis. For example, disruption of the global regulator of H 2 O 2 protection, oxyR, makes the freeliving strain extremely sensitive to H 2 O 2 but does not affect symbiosis (27).…”

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confidence: 99%

Disruption of sitA Compromises Sinorhizobium meliloti for Manganese Uptake Required for Protection against Oxidative Stress

Davies

Walker

2007

J Bacteriol

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During the initial stages of symbiosis with the host plant Medicago sativa, Sinorhizobium meliloti must overcome an oxidative burst produced by the plant in order for proper symbiotic development to continue. While identifying mutants defective in symbiosis and oxidative stress defense, we isolated a mutant with a transposon insertion mutation of sitA, which encodes the periplasmic binding protein of the putative iron/ manganese ABC transporter SitABCD. Disruption of sitA causes elevated sensitivity to the reactive oxygen species hydrogen peroxide and superoxide. Disruption of sitA leads to elevated catalase activity and a severe decrease in superoxide dismutase B (SodB) activity and protein level. The decrease in SodB level strongly correlates with the superoxide sensitivity of the sitA mutant. We demonstrate that all free-living phenotypes of the sitA mutant can be rescued by the addition of exogenous manganese but not iron, a result that strongly implies that SitABCD plays an important role in manganese uptake in S. meliloti.

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“…However, the level of stress experienced by bacteria in the infection thread due to ROS is unknown. Single mutants in any of the three S. meliloti catalases, one of the two superoxide dismutases (sodB) or in the global regulator of H 2 O 2 protection, oxyR, are sensitive to ROS, but are not defective in symbiosis [53][54][55][56] . However, double mutants in the genes encoding catalase B and catalase C (katB/katC) or catalase A and catalase C (katA/katC) are compromised in their ability to invade the host plant 53,54 .…”

Section: Sinorhizobium Meliloti Succinoglycan Biosynthesismentioning

confidence: 99%

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

et al. 2007

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Nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. Once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. Bacterial differentiation and nitrogen fixation are dependent on the microaerobic environment and other support factors provided by the plant. In return, the plant receives nitrogen from the bacteria, which allows it to grow in the absence of an external nitrogen source. Here, we review recent discoveries about the mutual recognition process that allows the model rhizobial symbiont Sinorhizobium meliloti to invade and differentiate inside its host plant alfalfa (Medicago sativa) and the model host plant barrel medic (Medicago truncatula).The recent completion of the Sinorhizobium meliloti genome sequence, and the progress towards the completion of the Medicago truncatula genome sequence, have led to a surge in the molecular characterization of the determinants that are involved in the development of the symbiosis between rhizobial bacteria and leguminous plants. Aromatic compounds from legumes called flavonoids first signal the rhizobial bacteria to produce lipochitooligosaccharide compounds called Nod factors 1 . Nod factors that are secreted by the bacteria activate multiple responses in the host plant that prepare the plant to receive the invading bacteria. Nod factors and symbiotic exopolysaccharides induce the plant to form infection threads, which are thin tubules filled with bacteria that penetrate into the plant cortical tissue and deliver the bacteria to their target cells. Plant cells in the inner cortex internalize the invading bacteria in host-membrane-bound compartments that mature into structures known Correspondence to G.C.W. gwalker@mit.edu. Competing interests statementThe authors declare no competing financial interests. DATABASES Invasion of plant rootsAlthough plant roots are exposed to various micro-organisms in the soil, their cell walls form a strong protective barrier against most harmful species. The early steps in the invasion of barrel medic (M. truncatula) and alfalfa (Medicago sativa) roots by S. meliloti are characterized by the reciprocal exchange of signals that allow the bacteria to use the plant root hair cells as a means of entry. Initial signal exchangeFlavonoid compounds (2-phenyl-1,4-benzopyrone derivatives) produced by leguminous plants are the first signals to be exchanged by host-rhizobial symbiont pairs 1 (FIG. 1). Flavonoids bind bacterial NodD proteins, which are members of the LysR family of transcriptional regulators, and activate these proteins to induce the transcription of rhizobial genes 1,2 . For example, the M. sativa-derived flavonoid luteolin stimulates binding of an active form of NodD1 to an S. meliloti 'nod-box' p...

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The katA Catalase Gene Is Regulated by OxyR in both Free-Living and Symbiotic Sinorhizobium meliloti

Cited by 36 publications

References 40 publications

The response of the Rhizobium leguminosarum bv. trifolii wild-type and exopolysaccharide-deficient mutants to oxidative stress

The response of the Rhizobium leguminosarum bv. trifolii wild-type and exopolysaccharide-deficient mutants to oxidative stress

Disruption of sitA Compromises Sinorhizobium meliloti for Manganese Uptake Required for Protection against Oxidative Stress

How rhizobial symbionts invade plants: the Sinorhizobium–Medicago model

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