ThewhcAgene plays a negative role in oxidative stress response ofCorynebacterium glutamicum

In this study, we analyzed the whcA gene from Corynebacterium glutamicum, which codes for a homologue of the WhiB-family of proteins. Deletion of the gene did not affect the growth of the mutant cells, indicating that the whcA gene was not essential under ordinary growth conditions. However, cells overexpressing the protein not only showed retarded growth as compared with the wild-type or the DeltawhcA mutant cells but also showed increased sensitivity to a variety of oxidants, such as diamide, menadione, and hydrogen peroxide. Thioredoxin reductase activity was repressed in the whcA-overexpressing cells, whereas its activity in the DeltawhcA mutant strain was derepressed regardless of the presence of oxidative stress. The whcA gene was constitutively expressed throughout the growth phase and its expression level was not affected by oxidative stress. A set of proteins under the control of whcA were identified by two-dimensional polyacrylamide gel electrophoresis and they were annotated as NADH oxidase, alcohol dehydrogenase, quinone reductase, and cysteine desulfurase. The corresponding genes encoding the identified proteins were not transcribed in DeltasigH mutant cells. Collectively, these data suggest that the whcA gene of C. glutamicum plays a negative role in the sigH-mediated stress response pathway.