The copper-responsive regulator CsoR is indirectly involved in Bradyrhizobium diazoefficiens denitrification

Pacheco, Pedro J., Cabrera, Juan J., Jimenez-Levia, Andrea, Torres, Maria J., Gates, Andrew J. ORCID:, Bedmar, Eulogio J., Richardson, David J. ORCID:, Mesa, Socorro, Tortosa, Germán and Delgado (EEZ - CSIC), Maria J. (2023) The copper-responsive regulator CsoR is indirectly involved in Bradyrhizobium diazoefficiens denitrification. FEMS Microbiology Letters, 370. ISSN 0378-1097

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The soybean endosymbiont Bradyrhizobium diazoefficiens harbours the complete denitrification pathway that is catalysed by a periplasmic nitrate reductase (Nap), a copper (Cu)-containing nitrite reductase (NirK), a c-type nitric oxide reductase (cNor), and a nitrous oxide reductase (Nos), encoded by the napEDABC, nirK, norCBQD, and nosRZDFYLX genes, respectively. Induction of denitrification genes requires low oxygen and nitric oxide, both signals integrated into a complex regulatory network comprised by two interconnected cascades, FixLJ-FixK2-NnrR and RegSR-NifA. Copper is a cofactor of NirK and Nos, but it has also a role in denitrification gene expression and protein synthesis. In fact, Cu limitation triggers a substantial down-regulation of nirK, norCBQD, and nosRZDFYLX gene expression under denitrifying conditions. Bradyrhizobium diazoefficiens genome possesses a gene predicted to encode a Cu-responsive repressor of the CsoR family, which is located adjacent to copA, a gene encoding a putative Cu+-ATPase transporter. To investigate the role of CsoR in the control of denitrification gene expression in response to Cu, a csoR deletion mutant was constructed in this work. Mutation of csoR did not affect the capacity of B. diazoefficiens to grow under denitrifying conditions. However, by using qRT-PCR analyses, we showed that nirK and norCBQD expression was much lower in the csoR mutant compared to wild-type levels under Cu-limiting denitrifying conditions. On the contrary, copA expression was significantly increased in the csoR mutant. The results obtained suggest that CsoR acts as a repressor of copA. Under Cu limitation, CsoR has also an indirect role in the expression of nirK and norCBQD genes.

Item Type: Article
Uncontrolled Keywords: cu-responsive regulator,gene expression,nitric oxide reductase,nitrite reductase,medicine(all),sdg 13 - climate action,sdg 2 - zero hunger ,/dk/atira/pure/subjectarea/asjc/2700
Faculty \ School: Faculty of Science > School of Biological Sciences
UEA Research Groups: Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Organisms and the Environment
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Depositing User: LivePure Connector
Date Deposited: 15 Aug 2023 08:30
Last Modified: 14 Sep 2023 10:30
DOI: 10.1093/femsle/fnad084


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