InterPro domain: IPR039203

Arabidopsis RPW8.1 and RPW8.2 genes confer broad-spectrum resistance to powdery mildew [ 1 , 2 ]. RPW8.2 is specifically targeted to the extrahaustorial membrane (EHM), where it activates haustorium-targeted resistance against powdery mildew [ 3 ]. This family consists of RPW81 and RPW8.2, and homologues of RPW8 (HR), also known as RPW8-like proteins. HRs also contribute to basal resistance to powdery mildew, and HR1 to HR3 have been shown to localize to the EHM, suggesting that this could be a feature of the family [ 4 ].

Plants are attacked by a range of phytopathogenic organisms, including viruses, mycoplasma, bacteria, fungi, nematodes, protozoa and parasites. Resistance to a pathogen is manifested in several ways and is often correlated with a hypersensitive response (HR), localised induced cell death in the host plant at the site of infection [ 5 ]. The induction of the plant defence response that leads to HR is initiated by the plants recognition of specific signal molecules (elicitors) produced by the pathogen; R genes are thought to encode receptors for these elicitors. RPS2, N and L6 genes confer resistance to bacterial, viral and fungal pathogens.

Sequence analysis has shown that they contain C-terminal leucine-rich repeats, which are characteristic of plant and animal proteins involved in protein-protein interactions [ 6 ]. In addition, the sequences contain a conserved nucleotide-binding site towards their N-terminal.

1. Broad-spectrum mildew resistance in Arabidopsis thaliana mediated by RPW8. Science 291, 118-20
2. Ectopic expression of RESISTANCE TO POWDERY MILDEW8.1 confers resistance to fungal and oomycete pathogens in Arabidopsis. Plant Cell Physiol. 55, 1484-96
3. The powdery mildew resistance protein RPW8.2 is carried on VAMP721/722 vesicles to the extrahaustorial membrane of haustorial complexes. Plant J. 79, 835-47
4. Homologues of the RPW8 Resistance Protein Are Localized to the Extrahaustorial Membrane that Is Likely Synthesized De Novo. Plant Physiol. 173, 600-613
5. Molecular genetics of plant disease resistance. Science 268, 661-7