Transcriptional analysis and functional characterization of XCC1294 gene encoding a GGDEF domain protein in Xanthomonas
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ORIGINAL PAPER
Transcriptional analysis and functional characterization of XCC1294 gene encoding a GGDEF domain protein in Xanthomonas campestris pv. campestris Yi-Min Hsiao · Wan-Ling Song · Chao-Tsai Liao · I-Hsuan Lin · Mei-Ying Pan · Ching-Fen Lin
Received: 29 June 2011 / Revised: 27 September 2011 / Accepted: 4 October 2011 / Published online: 16 October 2011 © Springer-Verlag 2011
Abstract The nucleotide cyclic di-GMP is a second messenger in bacteria that regulates a range of cellular functions including the virulence of pathogens. GGDEF is a protein domain involved in the synthesis of cyclic di-GMP. The genome of the crucifer pathogen Xanthomonas campestris pv. campestris (Xcc) encodes 21 proteins with a GGDEF domain. Clp, a homolog of the model transcription factor Crp of Escherichia coli, is a global regulator in Xcc. The aim of this study is to identify genes encoding GGDEF domain proteins whose expression is regulated by Clp. Results of reporter assay and RT-PCR analysis suggested that Clp regulates the expression of a set of genes encoding proteins harboring GGDEF domain. The transcription initiation site of XCC1294, one of the Clp regulated gene encoding a GGDEF domain protein, was mapped. Promoter analysis and gel retardation assay indicated that the transcription of XCC1294 is positively and directly regulated by Clp. Furthermore, transcription of XCC1294 was subject to catabolite repression and aVected by several stress conditions. We also showed that mutation of XCC1294 results in enhanced surface attachment. In addition, transcription of
Communicated by Jorge Membrillo-Hernandez. Y.-M. Hsiao (&) · W.-L. Song · C.-T. Liao · M.-Y. Pan · C.-F. Lin Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan e-mail: [email protected] W.-L. Song Institute of Medicine, Chung Shan Medical University, Taichung 402, Taiwan I.-H. Lin Institute of Medical Biotechnology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan
three putative adhesin genes (xadA, fhaC, and yapH) was increased in the XCC1294 mutant. Taken together, the data presented here indicate that Clp positively regulates expression of XCC1294, and that XCC1294 serves a regulator of bacterial attachment and regulates diVerent adhesin genes expression. Keywords Cyclic AMP receptor protein-like protein · Reporter assay · Transcriptional regulation · Xanthomonas campestris pv. campestris
Introduction Cyclic di-GMP is a ubiquitous second messenger involved in the regulation of various biological functions in diverse bacteria (Jenal and Malone 2006; Romling and Amikam 2006; Ryan et al. 2006b). Three protein domains are implicated in the synthesis and degradation of this molecule. The GGDEF domain is a diguanylate cyclase involved in cyclic di-GMP synthesis, whereas the EAL and HD-GYP domains are cyclic di-GMP phosphodiesterases (Tamayo et al. 2005; Dow et al. 2006; Jenal and Malone 2006). These three domains are broadly distributed among bacterial
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