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J. Bacteriol. doi:10.1128/JB.01722-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Expression analysis of multiple dnaK genes in cyanobacterium Synechococcus elongatus PCC 7942

Department of Bioscience, Tokyo University of Agriculture, Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan

^* To whom correspondence should be addressed. Email: hiyoshik{at}nodai.ac.jp.

	Abstract

We analyzed the stress responses of 3 dnaK homologues (dnaK1, dnaK2 and dnaK3) in the cyanobacterium Synechococcus elongatus PCC 7942. Reporter assay showed that under stress conditions, the expression of only the dnaK2 gene was induced, suggesting functional assignment of these homologues. RNA blot hybridization indicated a typical stress response of dnaK2 to heat- and high-light stress. Primer extension mapping showed that dnaK2 was transcribed from similar sites under various stress conditions. While no known sequence motif was detected in the upstream region, a 20-bp sequence element was highly conserved in dnaK2; it was essential not only for the stress induction but also the basal expression of dnaK2. The ubiquitous upstream localization of this element in each heat shock gene suggests its important role in the cyanobacterial stress response.