Poster: Plant Pathogen/Symbiont Interactions

Abs # 693: Genomic analysis of the clubroot infection of Arabidopsis thaliana caused by the pathogen Plasmodiophora brassicae

Presenter:	Ludwig-Mueller, Jutta , jutta.ludwig-mueller@mailbox.tu-dresden.de
Authors	Ludwig-Mueller, Jutta  (A)   Siemens, Johannes  (A)   Keller, Ingo  (B)   Schuller, Astrid  (A)   Nagel, Wolfgang  (B)   Parniske, Martin  (C)
Affiliations:	(A): Technische Universitaet Dresden, Institute for Botany (B): Technische Universitaet Dresden, Center for High Performance Computing (C): John Innes Centre, The Sainsbury Laboratory
Web Site:	http://www.biologie.tu-dresden.de/botanik/bot-home.html

The clubroot disease of Brassicaceae is one of the most damaging diseases within this plant family. Caused by an obligate biotrophic pathogen, the interaction between Plasmodiophora brassicae and its host is difficult to analyze. Since Arabidopsis thaliana is a good host for P. brassicae we have used the 22K microarray (Affymetrix) to investigate host gene expression during the development of the disease. Two time points were chosen, which are significantly different from each other. At the early time point (10 days after inoculation) small secondary plasmodia of the pathogen are visible, but only about 20% of the host tissue is colonized with limited change of host cell and root morphology. At a later time point (23 days after inoculation) different developmental stages of the pathogen are present. More than 60% of the host root cells are colonized and the root morphology is drastically altered. At both time points more than 1000 genes were differentially expressed when mRNA from infected roots was compared with that from control roots of the same age. Only a few genes showed up-regulation at both time points. One of these is the gene for myrosinase associated protein. Cytokinin oxidase was down-regulated at both time points, but much stronger at the second time point. While the number of genes associated with growth and cell cycle was significantly enhanced at the first time point, this number decreased at the second time point. Genes involved in ethylene biosynthesis and perception were downregulated at the later time point. This coincided with the downregulation of a high number of defense genes. It is hypothesized that P. brassicae is able to circumvent the defense response of the host plant by a yet unknown mechanism.