Regulation of pelZ, a gene of the pelB-pelC cluster encoding a new pectate lyase of Erwinia chrysanthemi 3937

Abstract

The phytopathogenic enterobacterium Erwinia chrysanthemi 3937 produces five major and several secondary endo-pectate lyases encoded by the pel genes. Most of these genes are arranged in clusters on the bacterial chromosome. The genomic region surrounding the pelB-pelC cluster was supposed to be involved in the regulation of PelB and PelC synthesis. We demonstrated that the variation of pelB expression resulted from the titration of a regulatory protein by the gene adjacent to pelC. This gene was renamed pelZ since it encodes a protein of 420 amino acids with an endo-pectate lyase activity. Regulation of pelZ expression was investigated by using transcriptional fusions and a study of mRNA synthesis. Its transcription depends on different environmental conditions. It is induced in planta and in the presence of pectic catabolite products. This induction seems to be partially mediated by the KdgR protein but does not result from a direct interaction of KdgR with the pelZ 5 region. The transcription of pelZ leads to the synthesis of a monocistronic mRNA. However, the synthesis of a polycistronic mRNA from the pelC promoter, regulated by KdgR, is responsible for increased production of PelZ under inducing conditions. pelZ transcription is also controlled by pecT, which regulates some other pel genes, but it is independent of the pecS regulatory locus. The pelZ gene appears to be widespread in different strains of E. chrysanthemi. Moreover, a gene homologous to pelZ exists in Erwinia carotovora subsp. atroseptica adjacent to the cluster containing the pectate lyase-encoding genes pel1, pel2, and pel3. This conservation could reflect a significant role of PelZ in the pectinolytic system of Erwiniae. We showed pelZ is not a predominant virulence factor of E. chrysanthemi but is involved in host specificity.

Cloning of two pectate lyase genes from the marine Antarctic bacterium Pseudoalteromonas haloplanktis strain ANT/505 and characterization of the enzymes

“…Several pectate lyases from mesophilic bacteria, above all from members of the genus Erwinia but also from the gram-positive genus Bacillus, have been cloned and characterized (Pissavin et al 1996;Tardy et al 1997;Shevchik et al 1997;Bauer and Collmer 1997;Soriano et al 2000). Recently, a thermostable pectate lyase from a newly isolated thermophilic bacterium, Thermoanaerobacter italicus, has been isolated and characterized (Kozianowski et al 1997).…”

Identification of a bacterial pectin acetyl esterase in Erwinia chrysanthemi 3937

“…The pelA-E-D cluster also includes the gene pemA, encoding the major pectin methylesterase. The transcription of pemA and of the five major pel genes is sensitive to several environmental conditions (Hugouvieux-CottePattat et al, 1996). The main factor affecting their expression is induction in the presence of pectin, resulting from the intracellular formation of catabolic products such as 2-keto-3-deoxygluconate (KDG).…”

Detection of and Response to Signals Involved in Host-Microbe Interactions by Plant-Associated Bacteria

“…They were detected only when bacteria were grown on plant material or in synthetic medium with macerated plant extracts (29,263,412). Three genes, pelL, pelZ; and pelI, encoding three of these secondary pectate lyases, were cloned and characterized from a derivative of E. chrysanthemi strain 3937 (301,387,449). Transcription of all three genes was inducible by plant extracts as well as by pectate catabolic products.…”

“…Different pel genes are also expressed at different levels during infection and appear to be differentially regulated depending on the host plant and even on the types of tissues (113,300,311). It is well established that each Pel enzyme has particular properties (301,387,449) and may play specialized roles during infection. It has been shown that the role of each pectate lyase depends on the host plant (29,41), suggesting that the variety of Pel isoenzymes may result from specific adaptations of the bacteria to macerate different plant tissues.…”

“…Induction of pelZ seemed to be partially mediated by the KdgR protein but did not result from a direct interaction of KdgR with the pelZ 5Ј region. The transcription of pelZ occurs from multiple promoters, including one upstream of pelC, which is controlled by KdgR, leading to a bicistronic mRNA (387). Expression of pelZ is also controlled by pecT but is independent of PecS (387).…”