Functional analysis of a BarX homologue (SngA) as a pleiotropic regulator in Streptomyces natalensis
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ORIGINAL PAPER
Functional analysis of a BarX homologue (SngA) as a pleiotropic regulator in Streptomyces natalensis Kang-Mu Lee · Chang-Kwon Lee · Sun-Uk Choi · Hae-Ryong Park · Yong-Il Hwang
Received: 20 August 2007 / Revised: 22 December 2007 / Accepted: 4 January 2008 / Published online: 26 January 2008 © Springer-Verlag 2008
Abstract The prior sequencing of the upstream region of the -butyrolactone autoregulator receptor gene (sngR) in Streptomyces natalensis revealed the presence of a 972-bp gene encoding a BarX homologue (SngA), which acts as a pleiotropic regulator controlling secondary metabolism and morphological diVerentiation. In this study, we investigated the in vivo function of SngA in S. natalensis, by comparing the natamycin production, morphology, and transcription of genes related to natamycin biosynthesis in a wild-type strain and a sngA-deleted mutant. The disruption of sngA resulted in a decrease in natamycin production, and in the induction of pigment production that had not been previously observed from S. natalensis. On the other hand, the insertion of the intact sngA with its own promoter, into the wild-type strain, resulted in a 1.7-fold increase in natamycin production. Spore formation decreased in comparison to that of the wild-type strain when the sngA-deleted mutant was grown on YEME agar, MS medium, and ISP4 medium. All phenotypes were restored to the original wild-type phenotypes upon Communicated by Jorge Membrillo-Hernàndez. K.-M. Lee Division of Nano Sciences and Department of Life Science, Ewha Womans University, Seoul 120-750, Republic of Korea C.-K. Lee Department of Physiology and Anesthesiology, College of Medicine, Institute of Biomedical Science and Technology, Konkuk University, Danwol-dong 322, Choongju 380-701, Republic of Korea S.-U. Choi · H.-R. Park · Y.-I. Hwang (&) Department of Food Science and Biotechnology, Kyungnam University, Masan 631-701, Republic of Korea e-mail: [email protected] S.-U. Choi e-mail: [email protected]
complementation with the intact sngA, suggesting that SngA has pleiotropic functions in controlling both morphological diVerentiation and secondary metabolite production. Keywords Streptomyces natalensis · Pleiotropic regulator · Morphological diVerentiation · Natamycin production
Introduction Species of the soil-dwelling Streptomyces are known to produce a variety of antibiotics and other secondary metabolites that have numerous biological activities of interest to humankind. Complex biosynthetic pathways encoded by gene clusters, which include regulatory genes and antibiotic biosynthetic genes, synthesize these secondary metabolites. The -butyrolactone autoregulators found in the genus Streptomyces are regarded as microbial hormones that control morphological diVerentiation and/or the production of secondary metabolites. The -butyrolactone autoregulators have a 2,3-di-substituted -butyrolactone skeleton in common, and can be classiWed into three groups, which include A-factor type, virginiae butanolide (VB) type, and IM-2 type
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