Role of NorR-like transcriptional regulators under nitrosative stress of the δ-proteobacterium, Desulfovibrio gigas

NorR protein was shown to be responsible for the transcriptional regulation of flavorubredoxin and its associated oxidoreductase in Escherichia coli. Since Desulfovibrio gigas has a rubredoxin:oxygen oxidoreductase (ROD) that is involved in both oxidative and nitrosative stress response, a NorR-like protein was searched in D. gigas genome. We have found two putative norR coding units in its genome. To study the role of the protein designated as NorRl-like (NorR1L) in the presence of nitrosative stress, a norR1L null mutant of D. gigas was created and a phenotypic analysis was performed under the nitrosating agent GSNO. We show that under these conditions, the growth of both D. gigas mutants Delta roo and Delta norR1-like is impaired. In order to confirm that D. gigas NorR1 -like may play identical function as the NorR of E. coli, we have complemented the E. coli Delta norR mutant strain with the norR1-like gene and have evaluated growth when nitrosative stress was imposed. The growth phenotype of E. coli Delta norR mutant strain was recovered under these conditions. We also found that induction of roo gene expression is completely abolished in the norR1L mutant strain of D. gigas subjected to nitrosative stress. It is identified in delta-proteobacteria, for the first time a transcription factor that is involved in nitrosative stress response and regulates the rd-roo gene expression. (C) 2013 Elsevier Inc. All rights reserved.