Redox-sensitive fluorescent biosensors detect Sinorhizobium meliloti intracellular redox changes under free-living and symbiotic lifestyles

Pacoud, Marie; Mandon, Karine; Cazareth, Julie; Pierre, Olivier; Frendo, Pierre; Alloing, Geneviève

doi:10.1016/j.freeradbiomed.2022.03.030

Cited by 4 publications

(5 citation statements)

References 56 publications

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“…The basal oxidation level of roGFP2-Orp1 was similar in WT and ΔsydR strains, corresponding to a highly reducing redox potential EroGFP2 (−290 mV) as previously reported (8). Upon addition of oxidants, similar kinetics of roGFP2-Orp1 oxidation were observed in WT and Δ sydR mutant strains.…”

Section: Resultssupporting

confidence: 86%

“…The effect of sydR inactivation on bacteria challenged with ROS was further analyzed by using the genetically encoded biosensor roGFP2-Orp1. This redox probe proved to be an accurate tool for measuring dynamic changes in intracellular H 2 O 2 pool in S. meliloti (8). The roGFP2-Orp1 is directly oxidized by H 2 O 2 , and it can also react with other peroxides and NaOCl, potentially responding to these oxidants in bacterial cultures (22, 23).…”

Section: Resultsmentioning

confidence: 99%

“…Real-time measurements of intracellular redox potential. Variations in intracellular redox potential of S. meliloti were monitored with ratiometric roGFP2 fluorescence measurements (excitation at 405 and 488 nm wavelenghts, emission at 515 nm) using a spectrofluorimeter luminometer (Xenius, Safas, Monaco), as previously described (8).…”

Section: Methodsmentioning

confidence: 99%

“…ROS play an important role during all steps of symbiosis development, and changes in ROS concentration have been detected from the early stage of interaction to mature nodules (7). A recent analysis using redox biosensors has established that the microsymbiont maintains a reduced state inside IT and undergoes an oxidative upshift during bacteroid differentiation (8). Moreover, several genes involved in the antioxidant defense of the microsymbiont have been known to be required for optimal symbiosis (9).…”

Section: Introductionmentioning

confidence: 99%

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SydR, a redox-sensing MarR-type regulator ofSinorhizobium meliloti, is crucial for symbiotic infection ofMedicago truncatularoots

Nazaret,

Farajzadeh,

Mejias

et al. 2023

Preprint

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Rhizobia associate with legumes and induce the formation of nitrogen-fixing nodules. The regulation of bacterial redox state plays a major role in symbiosis and Reactive Oxygen Species (ROS) produced by the plant are known to activate signaling pathways. However, only a few redox-sensing transcriptional regulators (TRs) have been characterized in the microsymbiont. Here, we describe SydR, a novel redox-sensing TR of S. meliloti that is essential for the establishment of symbiosis with Medicago truncatula. SydR, a MarR-type TR, represses the expression of the adjacent gene SMa2023 in growing cultures, and this repression is alleviated by NaOCl, tert-butyl, or H2O2 treatment. Gels shift assays strongly suggest that SydR binds to TATCGCGATA motif in the sydR-SMa2023 intergenic region in a redox-dependent manner. Furthermore, site-directed mutagenesis demonstrated that the oxidative inhibition of SydR involves the formation of an intermolecular C16-C16 disulfide bond. The inactivation of sydR did not alter the sensitivity of S. meliloti to NaOCl, tert-butyl, or H2O2, nor did it affect the response to oxidants of the roGFP2-Orp1 redox biosensor expressed within bacteria. However, in planta, delta sydR mutation impaired the formation of root nodules. Microscopic observations and analyses of marker gene expression showed that the delta sydR mutant is arrested at an early stage of the bacterial infection process. Altogether, these results demonstrated that SydR is a redox sensing MarR-type TR that plays a key role in the regulation of symbiosis with M. truncatula.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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SydR, a redox-sensing MarR-type regulator ofSinorhizobium meliloti, is crucial for symbiotic infection ofMedicago truncatularoots

Nazaret,

Farajzadeh,

Mejias

et al. 2023

Preprint

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“…Indeed, plants have adapted molecular weapons as reactive oxygen and nitrogen species, or Nodule Cysteine-Rich peptides (antimicrobial peptide equivalents) to control bacteria throughout the interaction [ 58-60 ]. In the fixation zone, growth-arrested bacteroids, supplied by plant C4-dicarboxylates, must assume nitrogen fixation reaction, costly in energy, in acidic [ 61 ], oxidizing [ 62 ], and microoxic conditions [ 1 ]. The microsymbiont is thus exposed to various micro-environments and signals that could stimulate TA activation in planta .…”

Section: Discussionmentioning

confidence: 99%

VapC10 toxin of the legume symbiont Sinorhizobium meliloti targets tRNASer and controls intracellular lifestyle

Syska,

Kiers,

Rancurel

et al. 2024

The ISME Journal

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The soil bacterium Sinorhizobium meliloti can establish a nitrogen fixing symbiosis with the model legume Medicago truncatula. The rhizobia induce the formation of a specialized root organ called nodule, where they differentiate into bacteroids and reduce atmospheric nitrogen into ammonia. Little is known on the mechanisms involved in nodule senescence onset and in bacteroid survival inside the infected plant cells. Whereas Toxin-Antitoxin (TA) systems have been shown to promote intracellular survival within host cells in human pathogenic bacteria, their role in symbiotic bacteria was rarely investigated. S. meliloti encodes several TA systems, mainly of the VapBC family. Here we present the functional characterization, through a multidisciplinary approach, of the VapBC10 TA system of S. meliloti. Following a MORE RNA-seq analysis, we demonstrated that the VapC10 toxin is an RNase that cleaves the anticodon loop of two tRNASer. Thereafter, a bioinformatics approach was used to predict VapC10 targets in bacteroids. This analysis suggests that toxin activation triggers a specific proteome reprogramming that could limit nitrogen fixation capability and viability of bacteroids. Accordingly, a vapC10 mutant induces a delayed senescence in nodules, associated to an enhanced bacteroid survival. VapBC10 TA system could contribute to S. meliloti adaptation to symbiotic lifestyle, in response to plant nitrogen status.

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Cadmium exposure induced light/dark- and time-dependent redox changes at subcellular level in Arabidopsis plants

Collado-Arenal,

Exposito-Rodriguez,

Mullineaux

et al. 2024

Journal of Hazardous Materials

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Redox-sensitive fluorescent biosensors detect Sinorhizobium meliloti intracellular redox changes under free-living and symbiotic lifestyles

Cited by 4 publications

References 56 publications

SydR, a redox-sensing MarR-type regulator ofSinorhizobium meliloti, is crucial for symbiotic infection ofMedicago truncatularoots

SydR, a redox-sensing MarR-type regulator ofSinorhizobium meliloti, is crucial for symbiotic infection ofMedicago truncatularoots

VapC10 toxin of the legume symbiont Sinorhizobium meliloti targets tRNASer and controls intracellular lifestyle

Cadmium exposure induced light/dark- and time-dependent redox changes at subcellular level in Arabidopsis plants

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