Expression of heat-shock genesgroESLinXanthomonas campestrisis upregulated by CLP in an indirect manner

Abstract

CLP is a homologue of cyclic AMP-receptor protein in Xanthomonas campestris. In this study, proteomic analysis and Western blotting showed that the clp mutant (TC820) of X. campestris synthesizes less GroESL proteins than the parental P20H. The groESL upstream regions, nt -583 to -32 (552 bp) and nt -178 to -29 (150 bp) relative to the groESL initiation codon, were cloned for transcriptional fusion assays. The 150-bp region, bearing putative sigma24- and sigma32-binding sites and the CIRCE element all known to regulate groESL operon, expressed the same levels of beta-galactosidase (300 U/ml) in both strains, indicating that CLP is not involved in the expression from this region. At early exponential phase, the 552-bp region displayed extremely high levels of promoter activity, 11,000 U/ml in P20H versus 5000 U/ml in TC820. The enzyme levels were about 2000 U/ml at stationary phase in both strains, indicating high levels of expression when cells cease growing. These results suggest that the sequence responding to CLP regulation resides between nt -178 and -583. However, since this region has no CLP-binding site and showed no binding to CLP in gel retardation assay, CLP is likely acting indirectly. This communication appears to be the first description of the positive regulation of a bacterial heat-shock operon by a CRP homologue.

Xanthomonas campestris cell–cell communication involves a putative nucleotide receptor protein Clp and a hierarchical signalling network

“…In addition to the genes encoding extracellular enzymes and EPS synthesis, Clp also regulates a range of other genes encoding flagellum synthesis, protein metabolism, multidrug resistance, Hrp system, iron uptake, TCA cycle, respiration and membrane components, and fatty acid metabolism. The data are agreeable with the previous genetic studies that Clp regulates the transcriptional expression of varied genes in different Xcc strains, including the cellulasea gene engXCA , the protease gene ptr1 , the flagellin gene fliC and the heat‐shock protein gene groESL (de Crecy‐Lagard et al ., 1990; Hsiao and Tseng, 2002; Lee et al ., 2003; Chang et al ., 2005; Hsiao et al ., 2005).…”

Quorum sensing and virulence regulation inXanthomonas campestris

“…However, the null mutation of clp in Xcc strain NRRLB1459 does not affect the utilization of various carbon sources but instead decreases the biosynthesis of EPS, extracellular cellulase, and polygalacturonate lyase (de Crecy‐Lagard et al ., 1990), the phenotypes similar to those of the DSF‐deficient mutants (Barber et al ., 1997; Slater et al ., 2000; Wang et al ., 2004). In addition, the transcriptional expression of several DSF‐regulated genes (He et al ., 2006a), including the cellulase gene engXCA , the protease gene ptr1 , the flagellin gene fliC , and the heat‐shock protein gene groESL , is also positively regulated by Clp in different Xcc strains (de Crecy‐Lagard et al ., 1990; Hsiao & Tseng, 2002; Lee et al ., 2003; Chang et al ., 2005; Hsiao et al ., 2005). These original findings, as well as the observation that the transcriptional expression of clp is influenced by DSF and dependent on the RpfC/RpfG two‐component system (He et al ., 2006b, 2007), strongly suggest a key role of Clp in the DSF regulatory pathway.…”

Regulation of the Type II Secretion Structural Gene xpsE in Xanthomonas campestris Pathovar campestris by the Global Transcription Regulator Clp

“…However, the leaf symptoms caused by WTM and XC472C strains appeared 1-2 days later than the wild-type strain 8004 (data not shown). Clp regulates a large set of genes directly or indirectly [1,3,8,9,10]. Therefore, it is possible that in WTM and XC472C strains some unknown virulence genes were also downregulated to such low levels that the virulence of Xcc was affected.…”

“…Clp usually regulates the synthesis of extracellular enzymes indirectly [1,10]. However, a recent study has shown that Clp binds to a specific sequence within the Fig.…”

“…Mutation in clp causes significant reduction of extracellular enzymes, pigments, and xanthan gum with the concomitant loss of virulence [3]. The flagellin gene, flic, and the heat shock groESL genes are also controlled by Clp [1].…”