Molecular Cloning of ATR5^Emoy2 from Hyaloperonospora arabidopsidis, an Avirulence Determinant That Triggers RPP5-Mediated Defense in Arabidopsis

Abstract

RPP5 is the seminal example of a cytoplasmic NB-LRR receptor-like protein that confers downy mildew resistance in Arabidopsis thaliana. In this study, we describe the cloning and molecular characterization of the gene encoding ATR5(Emoy2), an avirulence protein from the downy mildew pathogen Hyaloperonospora arabidopsidis isolate Emoy2. ATR5(Emoy2) triggers defense response in host lines expressing the functional RPP5 allele from Landsberg erecta (Ler-0). ATR5(Emoy2) is embedded in a cluster with two additional ATR5-like (ATR5L) genes, most likely resulting from gene duplications. ATR5L proteins do not trigger RPP5-mediated resistance and the copy number of ATR5L genes varies among H. arabidopsidis isolates. ATR5(Emoy2) and ATR5L proteins contain a signal peptide, canonical EER motif, and an RGD motif. However, they lack the canonical translocation motif RXLR, which characterizes most oomycete effectors identified so far. The signal peptide and the N-terminal regions including the EER motif of ATR5(Emoy2) are not required to trigger an RPP5-dependent immune response. Bioinformatics screen of H. arabidopsidis Emoy2 genome revealed the presence of 173 open reading frames that potentially encode for secreted proteins similar to ATR5(Emoy2), in which they share some motifs such as EER but there is no canonical RXLR motif.

Involvement of the Electrophilic Isothiocyanate Sulforaphane in Arabidopsis Local Defense Responses

“…7). In this case, the accession Landsberg erecta and the enhanced disease resistance1 (eds1) mutant in the Wassilewskija-0 background were used as controls, as these lines are highly susceptible to the Cala2 isolate (Parker et al, 1996;Bailey et al, 2011). Sporulation at 4 dpi was markedly decreased when plants had been pretreated with sulforaphane before inoculation with Hpa Cala2.…”

Hyaloperonospora arabidopsidis ATR1 effector is a repeat protein with distributed recognition surfaces

“…Although the mechanisms of effector translocation are not well understood, a typical eukaryotic signal sequence found in all effectors is thought to mediate secretion out of the pathogen. In most effectors, oomycete-specific RxLR and dEER motifs promote further translocation of effectors into the host cell (3)(4)(5)(6)(7). Recently, genome sequences of Hpa and Phytophthora species allowed identification of numerous genes containing the conserved N-terminal signal peptide and RxLR-dEER motifs (8,9).…”

Phytophthora infestans effector Pi14054 is a novel candidate suppressor of host silencing mechanisms

“…It does possess an EER motif close to the predicted signal peptide cleavage site. A similar organisation is also found in the ATR5 effector from Hyaloperonospora arabidopsidis, recognised by the cytoplasmic resistance protein RPP5 from Arabidopsis thaliana (Bailey et al 2011). Using BLASTP and default search parameters, possible orthologs of Pi14054 (Fig.…”