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Bacterial polysaccharides suppress induced innate immunity by calcium chelation

Aslam, Shazia N. and Newman, Mari-Anne and Erbs, Gitte and Morrissey, Kate L. and Chinchilla, Delphine and Boller, Thomas and Jensen, Tina Tandrup and De Castro, Cristina and Ierano, Teresa and Molinaro, Antonio and Jackson, Robert W. and Knight, Marc R. and Cooper, Richard M.. (2008) Bacterial polysaccharides suppress induced innate immunity by calcium chelation. Current biology, Vol. 18, H. 14. pp. 1078-1083.

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Official URL: http://edoc.unibas.ch/dok/A5248780

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Abstract

Bacterial pathogens and symbionts must suppress or negate host innate immunity. However, pathogens release conserved oligomeric and polymeric molecules or MAMPs (Microbial Associated Molecular Patterns), which elicit host defenses [1], [2] and [3]. Extracellular polysaccharides (EPSs) are key virulence factors in plant and animal pathogenesis, but their precise function in establishing basic compatibility remains unclear [4], [5], [6] and [7]. Here, we show that EPSs suppress MAMP-induced signaling in plants through their polyanionic nature [4] and consequent ability to chelate divalent calcium ions [8]. In plants, Ca2+ ion influx to the cytosol from the apoplast (where bacteria multiply [4], [5] and [9]) is a prerequisite for activation of myriad defenses by MAMPs [10]. We show that EPSs from diverse plant and animal pathogens and symbionts bind calcium. EPS-defective mutants or pure MAMPs, such as the flagellin peptide flg22, elicit calcium influx, expression of host defense genes, and downstream resistance. Furthermore, EPSs, produced by wild-type strains or purified, suppress induced responses but do not block flg22-receptor binding in Arabidopsis cells. EPS production was confirmed in planta, and the amounts in bacterial biofilms greatly exceed those required for binding of apoplastic calcium. These data reveal a novel, fundamental role for bacterial EPS in disease establishment, encouraging novel control strategies.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Botanik > Pflanzenphysiologie Pathogenabwehr (Boller)
UniBasel Contributors:Boller, Thomas and Chinchilla, Delphine
Item Type:Article
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Cell Press
ISSN:0960-9822
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:23
Deposited On:22 Mar 2012 13:33

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