Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Role of the extracytoplasmic function sigma factor CarQ in oxidative response of Bradyrhizobium japonicum: Anchana Thaweethawakorn , Dylan Parks , Jae-Seong So , Woo-Suk Chang; J. Microbiol. 2015;53(8):526-534. Published online July 31, 2015; DOI: https://doi.org/10.1007/s12275-015-5308-9

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As a nitrogen-fixing bacterium, Bradyrhizobium japonicum can establish a symbiotic relationship with the soybean plant (Glycine max). To be a successful symbiont, B. japonicum must deal with plant defense responses, such as an oxidative burst. Our previous functional genomics study showed that carQ (bll1028) encoding extracytoplasmic function (ECF) sigma factor was highly expressed (107.8-fold induction) under oxidative stress. Little is known about the underlying mechanisms of how CarQ responds to oxidative stress. In this study, a carQ knock-out mutant was constructed using site-specific mutagenesis to identify the role of carQ in the oxidative response of B. japonicum. The carQ mutant showed a longer generation time than the wild type and exhibited significantly decreased survival at 10 mM H2O2 for 10 min of exposure. Surprisingly, there was no significant difference in expression of oxidative stress-responsive genes such as katG and sod between the wild type and carQ mutant. The mutant also showed a significant increase in susceptibility to H2O2 compared to the wild type in the zone inhibition assay. Nodulation phenotypes of the carQ mutant were distinguishable compared to those of the wild type, including lower numbers of nodules, decreased nodule dry weight, decreased plant dry weight, and a lower nitrogen fixation capability. Moreover, desiccation of mutant cells also resulted in significantly lower percent of survival in both early (after 4 h) and late (after 24 h) desiccation periods. Taken together, this information will provide an insight into the role of the ECF sigma factor in B. japonicum to deal with a plant-derived oxidative burst.

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Implication of the σ E Regulon Members OmpO and σ N in the Δ ompA 299–356 -Mediated Decrease of Oxidative Stress Tolerance in St
Ren-Hsuan Ku, Li-Hua Li, Yi-Fu Liu, En-Wei Hu, Yi-Tsung Lin, Hsu-Feng Lu, Tsuey-Ching Yang, Silvia T. Cardona
Microbiology Spectrum.2023;[Epub] CrossRef
Identification and Validation of Reference Genes for Expression Analysis in Nitrogen-Fixing Bacteria under Environmental Stress
Dylan Parks, Christian Peterson, Woo-Suk Chang
Life.2022; 12(9): 1379. CrossRef
MostSinorhizobium melilotiExtracytoplasmic Function Sigma Factors Control Accessory Functions
Claus Lang, Melanie J. Barnett, Robert F. Fisher, Lucinda S. Smith, Michelle E. Diodati, Sharon R. Long, Craig D. Ellermeier, Claude Bruand, Sarah Ades, Hans-Martin Fischer
mSphere.2018;[Epub] CrossRef

YlaC is an Extracytoplasmic Function (ECF) Sigma Factor Contributing to Hydrogen Peroxide Resistance in Bacillus subtilis: Han-Bong Ryu , Inji Shin , Hyung-Soon Yim , Sa-Ouk Kang; J. Microbiol. 2006;44(2):206-216.; DOI: https://doi.org/2363 [pii]

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Abstract: In this study, we have attempted to characterize the functions of YlaC and YlaD encoded by ylaC and ylaD genes in Bacillus subtilis. The GUS reporter gene, driven by the yla operon promoter, was expressed primarily during the late exponential and early stationary phase, and its expression increased as the result of hydrogen peroxide treatment. Northern and Western blot analyses revealed that the level of ylaC transcripts and YlaC increased as the result of challenge with hydrogen peroxide. A YlaC-overexpressing strain evidenced hydrogen peroxide resistance and a three-fold higher peroxidase activity as compared with a deletion mutant. YlaC-overexpressing and YlaD-disrupted strains evidenced higher sporulation rates than were observed in the YlaC-disrupted and YlaD-overexpressing strains. Analyses of the results of native polyacrylamide gel electrophoresis of recombinant YlaC and YlaD indicated that interaction between YlaC and YlaD was regulated by the redox state of YlaD in vitro. Collectively, the results of this study appear to suggest that YlaC regulated by the YlaD redox state, contribute to oxidative stress resistance in B. subtilis.

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