Cell type-specific gene expression changes in Arabidopsis thaliana roots in response to beneficial Pseudomonas simiae WCS417 rhizobacteria 
E. VERBON (1), L. Liberman (2), P. Benfey (2), C. Pieterse (3) (1) Utrecht Unversity, Netherlands; (2) Duke University, U.S.A.; (3) Utrecht University, Netherlands

Beneficial bacteria naturally present in soil increase plant growth and/or induce plant resistance to pathogen attack. Therefore, these bacteria have the potential to replace pesticides or fertilizers while sustaining or increasing crop yield. Understanding the mechanisms by which bacteria induce beneficial effects is fundamental to successful application in the field. Moreover, unraveling these mechanisms will provide valuable insight into fundamental plant processes, including plant-microbe signaling, plant development and plant immunity. We profiled gene expression changes within Arabidopsis thaliana roots 48 hours after colonization by the beneficial microbe Pseudomonas simiae WCS417 (formerly known as P. fluorescens WCS417). Previously, it has been shown that expression of the transcription factor MYB72 and its downstream target BGLU42 are fundamental to the induction of systemic resistance by this bacterium. Interestingly, BGLU42 is expressed specifically in root hair cells. Because of this cell-type specificity we assessed RNA expression changes in five cell populations within the Arabidopsis root. This approach enables detection of genes differentially expressed in individual cell types that may be masked by whole organ analysis. As expected, genes involved in response to external biotic stimuli are up-regulated after root colonization. More specifically, immunity related processes are up-regulated within the root, while some maturation and cell wall related processes are down-regulated. Our data provide further evidence that there are cell-type specific responses to P. simiae WCS417 that result in systemic beneficial effects in Arabidopsis.

Abstract Number: P9-317
Session Type: Poster