Multiple candidate effectors from the oomycete pathogen Hyaloperonospora arabidopsidis suppress host plant immunity.

Oomycete pathogens cause diverse plant diseases. To successfully colonize their hosts, they deliver a suite of effector proteins that can attenuate plant defenses. In the oomycete downy mildews, effectors carry a signal peptide and an RxLR motif.

Maintenance of genetic variation in plants and pathogens involves complex networks of gene-for-gene interactions.

The RPP13 [recognition of Hyaloperonospora arabidopsidis (previously known as Peronospora parasitica)] resistance (R) gene in Arabidopsis thaliana exhibits the highest reported level of sequence diversity among known R genes. Consistent with a co-evolutionary model, the matching effector protein ATR13 (A. thaliana-recognized) from H.

Differential recognition of highly divergent downy mildew avirulence gene alleles by RPP1 resistance genes from two Arabidopsis lines.

The perception of downy mildew avirulence (Arabidopsis thaliana Recognized [ATR]) gene products by matching Arabidopsis thaliana resistance (Recognition of Peronospora parasitica [RPP]) gene products triggers localized cell death (a hypersensitive response) in the host plant, and this inhibits pathogen development. The oomycete pathogen, therefore, is under selection pressure to alter the form of these gene products to prevent detection. That the pathogen maintains these genes indicates that they play a positive role in pathogen survival.

Host-parasite coevolutionary conflict between Arabidopsis and downy mildew.

Plants are constantly exposed to attack by an array of diverse pathogens but lack a somatically adaptive immune system. In spite of this, natural plant populations do not often suffer destructive disease epidemics. Elucidating how allelic diversity within plant genes that function to detect pathogens (resistance genes) counteracts changing structures of pathogen genes required for host invasion (pathogenicity effectors) is critical to our understanding of the dynamics of natural plant populations.

Use of suppression subtractive hybridization to identify downy mildew genes expressed during infection of Arabidopsis thaliana.

SUMMARY Peronospora parasitica is an obligate biotrophic oomycete that causes downy mildew in Arabidopsis thaliana and Brassica species. Our goal is to identify P. parasitica (At) genes that are involved in pathogenicity.

A genetic interval and physical contig spanning the Peronospora parasitica (At) avirulence gene locus ATR1Nd.

In Peronospora parasitica (At) (downy mildew), the genetic determinants of cultivar-specific recognition by Arabidopsis thaliana are the Arabidopsis thaliana-recognised (ATR) avirulence genes. We describe the identification of 10 amplified fragment length polymorphism (AFLP) markers that define a genetic mapping interval for the ATR1Nd avirulence allele, the presence of which is perceived by the RPP1Nd resistance gene. Furthermore, we have constructed a P.