15th International Conference on Arabidopsis Research - TAIR

T05-011
Transcriptome analysis of Arabidopsis clubroots
and disease resistance of CKX gene overexpressing
plants indicate a key role for cytokinin in disease
development
Siemens, Johannes(1), Keller, Ingo(2), Sarx, Johannes(1), Kunz, Sabine(1), Schuller,
Astrid(1), Nagel, Wolfgang(2), Schmülling, Thomas(3), Parniske, Martin(4), Ludwig-
Müller, Jutta(1)
1-TU Dresden, Institute of Botany
2-TU Dresden, Center for High Performance Computing
3-FU Berlin, Institute of Biology
4-John Innes Centre, The Sainsbury Laboratory
The clubroot disease of Brassicaceae is caused by the obligate biotrophic
protist, Plasmodiophora brassicae. Infected roots undergo a developmental
switch that results in the formation of aberrant roots (clubs). To investigate
host gene expression during the development of the disease we have used
Affymetrix chip (22k chip). Two time points were chosen, an early time
point, at which the pathogen has colonised the root but has induced only
very limited change of host cell and root morphology. At a later time point,
more than 60% of the host root cells were colonized and root morphology
was drastically altered. At both time points more than 1000 genes were
differentially expressed in infected versus control roots. These included
genes associated with growth and cell cycle, sugar phosphate metabolism
and defense. The involvement of plant hormones in club development was
further supported; genes involved in auxin homeostasis, such as nitrilases
and members of the GH3 family, were up-regulated, whereas genes involved
in cytokinin homeostasis (cytokinin synthases and cytokinin-oxidases/dehydrogenases)
were strongly down-regulated already at a very early time
point. Cytokinin oxidase/dehydrogenase overexpressing lines were disease
resistant, clearly indicating the importance of (protist-derived) cytokinin as a
key factor in clubroot disease development
T05 Interaction with the Environment 2 (Biotic)
T05-012
The jasmonate-insensitive mutant jin1 shows
increased resistance to biotrophic as well as
necrotrophic pathogens
Susanne Berger(1), Anja Nickstadt(1), Bart Thomma(3), Juergen Zeier(2), Christiane
Loeffler(2), Ivo Feussner(1), Jaakko Kangasjaervi(4), Dierk Scheel(1)
1-IPB Halle
2-University Wuerzburg
3-University Leuven
4-University of Helsinki
Jasmonic acid and related oxylipin compounds are plant signaling molecules
that are involved in the response to pathogens, insects, wounding and ozone.
To get further inside the role of jasmonates in stress signal transduction the
response of two jasmonate-signaling mutants, jin1 and jin4, to pathogens
and ozone was analyzed in this study. Upon treatment with the biotrophic
bacterial pathogen Pseudomonas syringae, endogenous jasmonate levels
increased in jin1 and jin4 similar to wild-type demonstrating that these
mutants are not defective in jasmonate biosynthesis. Jin1 but not jin4 is more
resistant to P. syringae and this higher resistance is accompanied by higher
levels of salicylic acid. Jin1 is also more resistant to the the necrotrophic
fungal pathogen Botrytis cinerea and shows wild-type sensitivity to ozone
while jin4 is more susceptible to B. cinerea and ozone. These results indicate
that the mutations in jin1 and jin4 affect different branches of the jasmonate
signaling pathway and provide support for a crosstalk between the jasmonate
and salicylate pathways. Additionally, in this combination of phenotypes, jin1
is unique among all other jasmonate-related mutants described so far.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin