Rapid activation of a novel plant defense gene is strictly dependent on the Arabidopsis RPM1 disease resistance locus.

Abstract

We cloned and sequenced cDNAs encoded by a novel plant defense gene, ELI3, from parsley and Arabidopsis thaliana. The predicted product shares no homology to known sequences. ELI3 mRNA accumulates in A. thaliana leaves in response to challenge with phytopathogenic Pseudomonas syringae strains. The timing and magnitude of this response are dictated by the genetics of the plant‐pathogen interaction being analyzed. During incompatible interactions, where resistance in the plant genotype Col‐0 is dictated by the dominant RPM1 locus, ELI3 mRNA accumulates to high levels 5–10 h post‐inoculation. This kinetic behavior is also generated by the presence of a cloned bacterial avirulence gene, in otherwise virulent bacteria, which triggers resistance mediated via RPM1 action. The phenotypic outcome is a hypersensitive resistance reaction visible 8–15 h post‐infiltration. Thus, the induction kinetics of ELI3 mRNA accumulation are consistent with a functional role for the ELI3 gene product in establishing the resistant phenotype. In contrast, during compatible interactions with the susceptible plant genotype Nd‐0, which is homozygous recessive at the rpm1 locus, ELI3 mRNA accumulates significantly only after 15 h. We show genetically that ELI3 activation is strictly dependent on the presence of dominant alleles at RPM1 using an assay generalizable to any pathogen induced plant defense phenomena.

Interference between Two Specific Pathogen Recognition Events Mediated by Distinct Plant Disease Resistance Genes.

“…At least five Pseudomonas syringae avr genes are recognized by four unlinked Arabidopsis R genes (Dangl, 1993;Kunkel, 1995). The combinations analyzed in our experiments are avrRpt2-RPS2 (Whalen et al, 1991;lnnes et al, 1993;Kunkel et al, 1993;Yu et al, 1993) and avrRpm7-RPM1 (Debeneret al, 1991;Dangl et al, 1992;Ritter and Dangl, 1995). The respective avrgenes have never been observed to be present in the same bacterial strain.…”

Genome-Wide Gene Expression Analysis Reveals a Critical Role for CRYPTOCHROME1 in the Response of Arabidopsis to High Irradiance

“…5). Two genes encoding components related to pathogen defense signaling ELI3-2 (At4g37990) and a WRKY family transcription factor, WRKY70 (At3g56400; Kiedrowski et al, 1992;Li et al, 2004), are misregulated in the hy5 mutant (Supplemental Table S6), suggesting that HY5 may be a key component of the cross talk between light and pathogen defense signaling. HY5 has been demonstrated to bind a G-box motif (Gao et al, 2004), and, consistent with this, bioinformatic analysis of our array data revealed that a classic G-box (CACGTG) or a G-box variant (CACGTH) were significantly enriched in the HY5 regulon versus the genomic average for these elements within Arabidopsis 500-bp promoter spaces (Table III).…”

Expression Pattern of Two Paralogs Encoding Cinnamyl Alcohol Dehydrogenases in Arabidopsis. Isolation and Characterization of the Corresponding Mutants

“…Some paralogs (AtCAD-1, AtCAD-E, and -F) are close to MsaCAD1, a gene known to be wound inducible in alfalfa, where the corresponding protein is active on a range of cinnamyl, benzyl, and aliphatic aldehyde substrates (Brill et al, 1999). The AtCAD-B paralogs corresponding to ELI-3 proteins have been studied previously and were originally identified as part of the defense response in parsley (Petroselinum crispum) and in Arabidopsis (Kiedrowski et al, 1992). Williamson et al (1995) and Somssich et al (1996) demonstrated that ELI-3 was neither a CAD nor a malate dehydrogenase but rather a benzyl alcohol dehydrogenase, which accepts various benzaldehyde substrates.…”