15th International Conference on Arabidopsis Research - TAIR

T05-021
Mutations in Arabidopsis RIN4 that affect the
virulence of AvrRpm1, AvrB, and AvrRpt2 and R-gene
mediated HR.
Han Suk Kim(1), Darrell Desveaux(1), Alex Singer(2), John Sondek(2), Jeff Dangl(1)
1-Department of Biology, University of North Carolina, Chapel Hill
2-Department of Pharmacology, University of North Carolina, Chapel Hill
RPM1-interacting protein 4 or RIN4 of Arabidopsis thaliana, is targeted
by three different Pseudomonas syringae Type III effector proteins, AvrB,
AvrRpm1, and AvrRpt2. Upon infection with P. syringae carrying either avrB
or avrRpm1of susceptible hosts (rpm1), RIN4 becomes phosphorylated and
plant disease occurs. During infection of susceptible hosts lacking RPS2
with P. syringae carrying avrRpt2, RIN4, however, is thought to be degraded-
proteolytically, perhaps contributing to pathogen growth. In RPS2 plants, the
AvrRpt2-driven disappearance of RIN4 is required to activate RPS2 function.
To determine whether or not RIN4 phosphorylation or proteolytic cleavage of
RIN4 is required for the virulence function of AvrB and AvrRpm1, or AvrRpt2,
we have made mutations in putative phosphorylation sites in RIN4 as well
as two highly conserved cysteine protease cleavage sites at the N- and
C-terminal ends of RIN4. We present data on transgenic Arabidopsis plants
transformed with either the RIN4 phosphorylation mutants or the N- and
C-terminal cysteine protease cleavage site mutants. We show the effect of
the RIN4 mutations on the ability of AvrB or AvrRpm1 and AvrRpt2 to cause
disease on susceptible hosts. In addition, the region of RIN4 responsible for
the interaction with AvrB contains one of the conserved cysteine protease
cleavage sites. We therefore also show what affect the RIN4 mutations has
on the ability of AvrRpt2 to interfere with the avirulence function of AvrB or
AvrRpm1. Since modifications of RIN4 are detected by RPM1 and RPS2, we
also show the effect of the RIN4 mutations on R-gene mediated hypersensitive
response (HR).
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T05-022
Searching For Novel Components Involved In Plant
Nonhost Disease Resistance In Arabidopsis
Landtag, Jörn(1), Westphal, Lore(1), Lipka, Volker(1), Dittgen, Jan(1), Schulze-
Lefert, Paul(1), Scheel, Dierk(1), Rosahl, Sabine(1, 4)
1-Leibniz Institute of Plant Biochemistry
2-Leibniz Institute of Plant Biochemistry
3-Max-Planck-Institut für Züchtungsforschung Köln
4-Max-Planck-Institut für Züchtungsforschung Köln
5-Max-Planck-Institut für Züchtungsforschung Köln
6-Leibniz Institute of Plant Biochemistry
7-Leibniz Institute of Plant Biochemistry
Nonhost disease resistance is the major form of disease resistance by plants
which is effective against the majority of parasitic microorganisms such as
bacteria, fungi and oomycetes. Plants have evolved several defence mechanisms
to protect themselves against invading pathogens. These include
preformed physical barriers like plant cytoskeleton as well as inducible
mechanisms like the hypersensitive response with cell death.
Here, we describe the characterization of a nonhost-pathosystem involving
the model plant Arabidopsis and the economically important oomycete
pathogen Phytophthora infestans. Cytological analysis of Arabidopsis wildtype
plants challenged with Phytophthora infestans spores revealed that the cell
wall penetration attempts are usually aborted and only few spores can trigger
a hypersensitive response with cell death.
To find novel components of the nonhost disease resistance we started
an EMS-mutagenesis approach. A microscope-based screen for altered
resistance phenotypes upon P. infestans challenge conducted with more
than 70.000 M2 plants allowed the isolation of several mutant plants with an
enhanced penetration frequency phenotype.
T05 Interaction with the Environment 2 (Biotic)