Arabidopsis RPP4 is a member of the RPP5 multigene family of TIR‐NB‐LRR genes and confers downy mildew resistance through multiple signalling components

Abstract

SummaryIn Arabidopsis, RPP4 confers resistance to Peronospora parasitica (P.p.) races Emoy2 and Emwa1 (downy mildew). We identi®ed RPP4 in Col-0 as a member of the clustered RPP5 multigene family encoding nucleotide-binding leucine-rich repeat proteins with Toll/interleukin-1 receptor domains. RPP4 is the orthologue of RPP5 which, in addition to recognizing P.p. race Noco2, also mediates resistance to Emoy2 and Emwa1. Most differences between RPP4 and RPP5 occur in residues that constitute the TIR domain and in LRR residues that are predicted to confer recognition speci®city. RPP4 requires the action of at least 12 defence components, including DTH9, EDS1, PAD4, PAL, PBS2, PBS3, SID1, SID2 and salicylic acid. The ndr1, npr1 and rps5-1 mutations partially compromise RPP4 function in cotyledons but not in true leaves. The identi®cation of RPP4 as a TIR-NB-LRR protein, coupled with its dependence on certain signalling components in true leaves, is consistent with the hypothesis that distinct NB-LRR protein classes differentially signal through EDS1 and NDR1. Our results suggest that RPP4-mediated resistance is developmentally regulated and that in cotyledons there is cross-talk between EDS1 and NDR1 signalling and processes regulating systemic acquired resistance.

A Gain-of-Function Mutation in a Plant Disease Resistance Gene Leads to Constitutive Activation of Downstream Signal Transduction Pathways in suppressor of npr1-1, constitutive 1

“…Colons indicate high amino acid identity, and dots indicate low identity. RPP4, Resistance to Peronospora parasitica 4 (van der Biezen et al, 2002); RPP5, Resistance to P. parasitica 5 (Parker et al, 1997); RPP1-WsA to RPP1-WsC, Resistance to P. parasitica 1, Arabidopsis thaliana accession Wassilewskija A to C (Botella et al, 1998); SSI4, suppressor of salicylic acid insensitivity of npr1-5, 4 (Shirano et al, 2002); N, Nicotiana glutinosa virus resistance gene (Whitham et al, 1994); RPS4, Resistance to Pseudomonas syringae 4 (Gassmann et al, 1999); L6, Linum usitatissimum rust resistance gene (Lawrence et al, 1995); RRS1-R, Resistance to Ralstonia solanacearum 1-recessive (Deslandes et al, 2002). (C) Locations of the snc1 mutation and amino acid changes in confirmed gain-of-function R protein variants that cause constitutive HR.…”

“…This region contains a cluster of RPP5 orthologs, including the recently cloned RPP4 (Parker et al, 1997;van der Biezen et al, 2002). The snc1 mutant phenotypes are suppressed completely by eds1 , but not by ndr1 , suggesting that SNC1 is located upstream of EDS1 and that one of the RPP5 homologs is activated constitutively in snc1 (Li et al, 2001).…”

“…Recently, it was proposed that the interaction of the NB-LRR and Avr proteins is indirect and may require a third host protein as a mediator (van der Biezen and Jones, 1998b;Dangl and Jones, 2001;Bonas and Lahaye, 2002). Activation of NB-LRR proteins results from the modification of host proteins by pathogen effectors rather than from direct interactions between NB-LRR and Avr proteins.…”

“…A number of R genes have been cloned from different species, and most of them encode proteins that contain nucleotide binding site (NB) and Leu-rich repeat (LRR) domains (Bent, 1996;Hammond-Kosack and Jones, 1997;Ellis et al, 2000). Some R proteins also contain a conserved ARC domain located between the NB and the LRR (van der Biezen and Jones, 1998a).…”

Regulation of plant innate immunity by three proteins in a complex conserved across the plant and animal kingdoms

“…At least two distinct disease resistance pathways have been described for Arabidopsis, governed by R-protein structural type rather than pathogen class (Aarts et al 1998). The R genes RPM1 (CC-NB-LRR type) and RPP4 (TIR-NB-LRR type) confer resistance to bacterial and oomycete pathogens expressing specific cognate avirulence gene products (Grant et al 1995;van der Biezen et al 2002). mos4-1, Atcdc5-1, and prl1-1 were more susceptible than wild type to both avirulent P.s.m.…”