A Novel Class of Eukaryotic Zinc-Binding Proteins Is Required for Disease Resistance Signaling in Barley and Development in C. elegans

Abstract

Barley Rar1 is a convergence point in the signaling of resistance to powdery mildew, triggered by multiple race-specific resistance (R) genes. Rar1 is shown to function upstream of H2O2 accumulation in attacked host cells, which precedes localized host cell death. We isolated Rar1 by map-based cloning. The sequence of the deduced 25.5 kDa protein reveals two copies of a 60-amino acid domain, CHORD, conserved in tandem organization in protozoa, plants, and metazoa. CHORD defines a novel eukaryotic Zn2+-binding domain. Silencing of the C. elegans CHORD-containing gene, chp, results in semisterility and embryo lethality, suggesting an essential function of the wild-type gene in nematode development. Our findings indicate that plant R genes have recruited a fundamental cellular control element for signaling of disease resistance and cell death.

Ubiquitination-mediated protein degradation and modification: an emerging theme in plant-microbe interactions

“…The plant SGT1 (Suppressor of G2 allele of skp1) gene was first isolated independently by two laboratories; one in the searching for interacting proteins for the key signaling component of multiple R-gene-mediated resistance, RAR1 [12], and the other in the screening for the genes essential for R gene RPP5-mediated disease resistance, respectively [92,93]. Studies from several groups indicated that SGT1 is required by a diverse range of R genes from different plant species in response to a variety of pathogens [61,[92][93][94][95].…”

Differential Requirement of Oryza sativa RAR1 in Immune Receptor-Mediated Resistance of Rice to Magnaporthe oryzae

“…The function of these proteins in disease resistance responses have been extensively investigated previously using mutant analyses Chandra-Shekara et al, 2004;Hubert el al., 2003;Lu et al, 2003;Shirasu et al, 1999;Takahashi et al, 2003) and by virus induced gene silencing (VIGS) analyses in several plant species (Bhattarai et al, 2007;de la Fuente van Bentem et al, 2005;Leister et al, 2005;Liu et al, 2004;Scofield et al, 2005). The data from these studies revealed differing specificities for these proteins in diverse NB-LRR-mediated resistance responses.…”

“…http://molcells.org Established in 1990 RAR1, encoding a eukaryotic zinc-binding protein, was originally identified in barley due to its requirement for the Mla12-mediated resistance to powdery mildew (Shirasu et al, 1999). It was later found to be essential for Mla6, but not Mla1, resistance (Azevedo et al, 2002).…”

Isolation and characterization of rice mutants compromised in Xa21-mediated resistance to X. oryzae pv. oryzae

“…For example, the barley Rar1 and Rar2 genes have partial resistance phenotypes in cultivars carrying several powdery mildew R genes (Shirasu et al 1999). The partial loss of resistance may indicate that genes required for disease resistance are redundant or part of branched pathways.…”

“…Subsequently, these genes were each shown to be required to transduce the signal of multiple R genes (Century et al 1997;Innes 1998). The cloned barley gene, Rar1, is required for multiple R gene-mediated resistance to powdery mildew pathways (Shirasu et al 1999).…”