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Open Access Research article

Acidic pH shock induces the expressions of a wide range of stress-response genes

Yoon Jung Kim1, Myung Hee Moon1, Jae Yang Song12, Colin P Smith2, Soon-Kwang Hong3 and Yong Keun Chang1*

Author Affiliations

1 Dept. of Chemical and Biomolecular Engineering (The Brain Korea 21 Program), Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701, Korea

2 Functional Genomics Laboratory, School of Biomedical and Molecular Sciences, University of Surrey, Guildford, GU2 7XH, UK

3 Division of Bioscience and Bioinformatics, Myung-Ji University, San 38-2 Namdong, Yongin, Kyunggido, 449-728, Korea

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BMC Genomics 2008, 9:604  doi:10.1186/1471-2164-9-604

Published: 16 December 2008

Abstract

Background

Environmental signals usually enhance secondary metabolite production in Streptomycetes by initiating complex signal transduction system. It is known that different sigma factors respond to different types of stresses, respectively in Streptomyces strains, which have a number of unique signal transduction mechanisms depending on the types of environmental shock. In this study, we wanted to know how a pH shock would affect the expression of various sigma factors and shock-related proteins in S. coelicolor A3(2).

Results

According to the results of transcriptional and proteomic analyses, the major number of sigma factor genes were upregulated by an acidic pH shock. Well-studied sigma factor genes of sigH (heat shock), sigR (oxidative stress), sigB (osmotic shock), and hrdD that play a major role in the secondary metabolism, were all strongly upregulated by the pH shock. A number of heat shock proteins including the DnaK family and chaperones such as GroEL2 were also observed to be upregulated by the pH shock, while their repressor of hspR was strongly downregulated. Oxidative stress-related proteins such as thioredoxin, catalase, superoxide dismutase, peroxidase, and osmotic shock-related protein such as vesicle synthases were also upregulated in overall.

Conclusion

From these observations, an acidic pH shock was considered to be one of the strongest stresses to influence a wide range of sigma factors and shock-related proteins including general stress response proteins. The upregulation of the sigma factors and shock proteins already found to be related to actinorhodin biosynthesis was considered to have contributed to enhanced actinorhodin productivity by mediating the pH shock signal to regulators or biosynthesis genes for actinorhodin production.