The alternative sigma factor HrpL negatively modulates the flagellar system in the phytopathogenic bacterium Erwinia amylovora under hrp-inducing conditions.
In this work we present evidence of an opposite regulation in the phytopathogenic bacteria Erwinia amylovora between the virulence-associated Type III secretion system (TTSS) and the flagellar system. Using loss-of-function mutants we show that motility enhanced the virulence of wild-type bacteria relative to a nonmotile mutant when sprayed on apple seedlings with unwounded leaves. Then we demonstrated through analyses of motility, flagellin export and visualization of flagellar filament that HrpL, the positive key regulator of the TTSS, also down-regulates the flagellar system. Such a dual regulation mediated by an alternative sigma factor of the TTSS appears to be a level of regulation between virulence and motility not yet described among Proteobacteria.
Cesbron
Sophie
S
UMR 077, INRA/INH/Université d'Angers [corrected] Beaucouzé, France. scesbron@angers.inra.fr
Paulin
Jean-Pierre
JP
Tharaud
Michel
M
Barny
Marie-Anne
MA
Brisset
Marie-Noëlle
MN
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D044084:Erwinia amylovora / Q000235:genetics* / Q000472:pathogenicity; D005408:Flagellin / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D027824:Rosaceae / Q000382:microbiology; D036226:Seedlings / Q000382:microbiology; D012808:Sigma Factor / Q000235:genetics*; D014774:Virulence
D001426:Bacterial Proteins; D012808:Sigma Factor; D005408:Flagellin