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Journal of Bacteriology, November 2009, p. 6473-6481, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00875-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Reciprocal Regulation between SigK and Differentiation Programs in Streptomyces coelicolor{triangledown} ,§

Xu-Ming Mao, Zhan Zhou, Xiao-Ping Hou, Wen-Jun Guan, and Yong-Quan Li*

Zhejiang University, College of Life Sciences, Hangzhou 310058, China

Received 3 July 2009/ Accepted 25 August 2009

Here we reported that deletion of SigK (SCO6520), a sigma factor in Streptomyces coelicolor, caused an earlier switch from vegetative mycelia to aerial mycelia and higher expression of chpE and chpH than that in the wild type. Loss of SigK also resulted in accelerated and enhanced production of antibiotics, actinorhodin, and undecylprodigiosin and increased expression of actII-orf4 and redD. These results suggested that SigK had a negative role in morphological transition and secondary metabolism. Furthermore, the sigK promoter (sigKp) activity gradually increased and sigK expression was partially dependent on SigK, but this dependence decreased during the developmental course of substrate mycelia. Meanwhile, two potentially nonspecific cleavages occurred between SigK and green fluorescent protein, and the SigK fusion proteins expressed under the constitutive promoter ermEp* sharply decreased and disappeared when aerial mycelia emerged. If expressed under sigKp, 3FLAG-SigK showed similar dynamic patterns but did not decrease as sharply as SigK expressed under ermEp*. These data suggested that the climbing expression of sigK might reduce the prompt degradation of SigK during vegetative hypha development for the proper timing of morphogenesis and that SigK vanished to remove the block for the emergence of aerial mycelia. Thus, we proposed that SigK had inhibitory roles on developmental events and that these inhibitory effects may be released by SigK degradation.

* Corresponding author. Mailing address: Zhejiang University, College of Life Sciences, Hangzhou 310058, China. Phone: 86-571-88206632. Fax: 86-571-88208569. E-mail: lyq{at}zju.edu.cn

{triangledown} Published ahead of print on 4 September 2009.

§ Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, November 2009, p. 6473-6481, Vol. 191, No. 21
0021-9193/09/$08.00+0     doi:10.1128/JB.00875-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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