Aboveground activation of defense leads to recruitment of bacteria into the rhizosphere of Arabidopsis thaliana
R. BERENDSEN (1), K. Yu (1), C. Pieterse (1), P. Bakker (1) (1) Utrecht University, Netherlands

Disease suppressive soils are soils in which plants remain healthy, despite the presence of a  virulent pathogen. Disease suppressiveness is related to the presence of specific bacteria that inhibit growth and activity of the pathogen. The development of disease supressiveness usually requires a severe disease outbreak, leading to the hypothesis that plants recruit beneficial bacteria upon attack to aid them in their defense. The mechanisms governing  this recruitment remain largely unknown. In this study, we investigated changes in the rhizosphere microbiome of the plant model Arabidopis thaliana upon attack by different aboveground pathogens. We observed that three  bacterial OTU’s were significantly more abundant  in the rhizosphere of plants infected by the biotrophic  pathogen Hyaloperonospora arabidopsidis than in the rhizosphere of control plants. In general, plants defend themselves against biotrophic pathogens using defense signaling pathways dependent on the plant hormone salicylic acid (SA), whereas defense against necrotrophic pathogens is dependent on jasmonic acid. Our results indicate that  SA-dependent defense signaling pathways are  involved in recruitment of bacteria upon attack. We isolated the recruited OTUs from rhizospheres of  Hyaloperonospora-infected plants. The three isolates interact synergistically in biofilm formation and this may explain their recruitment as a cohort. In addition, we have investigated the biological relevance of this recruitment and explored their direct and indirect effects against plant pathogens.

Abstract Number: C7-6, P1-11
Session Type: Concurrent