J. Boch et al., ANALYSIS OF RESISTANCE GENE-MEDIATED DEFENSE RESPONSES IN ARABIDOPSIS-THALIANA PLANTS CARRYING A MUTATION IN CPR5, Molecular plant-microbe interactions, 11(12), 1998, pp. 1196-1206
In resistant plants, pathogen attack often leads to rapid activation o
f defense responses that limit multiplication and spread of the pathog
en. To investigate the signaling mechanisms underlying this process, m
e carried out a screen for mutants in the signaling pathway governing
resistance in Arabidopsis thaliana to the bacterial pathogen Pseudomon
as syringae. This involved screening for suppressor mutations that res
tored resistance to a susceptible line carrying a mutation in the RPS2
resistance gene. A mutant that conferred resistance by activating def
ense responses in the absence of pathogens was isolated. This mutant,
which carries a mutation at the CPR5 locus and was thus designated cpr
5-2, exhibited resistance to P. syringae, spontaneous development of n
ecrotic lesions, elevated PR gene expression in the absence of pathoge
ns, and abnormal trichomes. Resistance gene-mediated defenses, includi
ng the hypersensitive response, restriction of pathogen growth, and in
duction of defense-related gene expression, were functional in cpr5-2
mutant plants. Additionally, in cpr5-2 plants RPS2-mediated induction
of PR-1 expression was enhanced, whereas RPM1-mediated induction of EL
13 was not. These findings suggest that CPR5 encodes a negative regula
tor of the RPS2 signal transduction pathway.