It’s a sticky business – the role of Pseudomonas exopolysaccharides and motility during plant infection
S. PFEILMEIER (1), C. Zipfel (2), J. Malone (3) (1) The Sainsbury Laboratory / John Innes Centre, United Kingdom; (2) The Sainsbury Laboratory, United Kingdom; (3) John Innes Centre, United Kingdom

Plasma membrane-localized pattern recognition receptors (PRRs) perceive microbe-associated molecular patterns (MAMPs), leading to pattern-triggered immunity (PTI). Pathogenic and commensal bacteria must employ strategies to evade and/or suppress PTI in order to successfully colonize host plants. Biofilm formation and motility represent contrasting bacterial lifestyles controlled by the secondary messenger cyclic-di-GMP. We show that both production of exopolysaccharides (EPS) and flagella-driven motility are important factors in Pseudomonas syringae pv. tomato (Pto) DC3000 during different stages of the infection process on Arabidopsis thaliana. Besides surface adhesion and stress protection, a role has also been suggested for EPS in evasion of PTI. During infection, the flagellum has an ambiguous role, acting as virulence factor and also as immunogen as a result of the recognition of its main building block, flagellin, by FLAGELLIN SENSING2 (FLS2). Therefore, strict control of flagella synthesis is important for plant-associated bacteria. Elevated cyclic-di-GMP levels in the pathogen Pto DC3000 and the commensal P. protegens Pf-5 inhibit flagellin synthesis and help the bacteria to evade FLS2-mediated defence. However, high cellular cyclic-di-GMP levels were shown to drastically reduce the virulence of Pto DC3000. We propose that this is a result of reduced flagellar motility and/or additional pleiotropic effects of cyclic-di-GMP signalling on bacterial behaviour.

Abstract Number: P6-148
Session Type: Poster