TY - JOUR
T1 - Bacterial polysaccharides suppress induced innate immunity by calcium chelation
AU - Aslam, Shazia N
AU - Newman, Mari-Anne
AU - Erbs, Gitte
AU - Morrissey, Kate L
AU - Chinchilla, Delphine
AU - Boller, Thomas
AU - Jensen, Tina Tandrup
AU - De Castro, Cristina
AU - Ierano, Teresa
AU - Molinaro, Antonio
AU - Jackson, Robert W
AU - Knight, Marc R
AU - Cooper, Richard M
PY - 2008/7/22
Y1 - 2008/7/22
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=51749125931&partnerID=8YFLogxK
UR - http://dx.doi.org/10.1016/j.cub.2008.06.061
U2 - 10.1016/j.cub.2008.06.061
DO - 10.1016/j.cub.2008.06.061
M3 - Article
SN - 0960-9822
VL - 18
SP - 1078
EP - 1083
JO - Current Biology
JF - Current Biology
IS - 14
ER -