The Arabidopsis TIR-NB-LRR Gene RAC1 Confers Resistance to Albugo candida (White Rust) and Is Dependent on EDS1 but not PAD4

Abstract

Resistance to Albugo candida isolate Acem1 is conferred by a dominant gene, RAC1, in accession Ksk-1 of Arabidopsis thaliana. This gene was isolated by positional cloning and is a member of the Drosophila toll and mammalian interleukin-1 receptor (TIR) nucleotide-binding site leucine-rich repeat (NB-LRR) class of plant resistance genes. Strong identity of the TIR and NB domains was observed between the predicted proteins encoded by the Ksk-1 allele and the allele from an Acem1-susceptible accession Columbia (Col) (99 and 98%, respectively). However, major differences between the two predicted proteins occur within the LRR domain and mainly are confined to the β-strand/β-turn structure of the LRR. Both proteins contain 14 imperfect repeats. RAC1-mediated resistance was analyzed further using mutations in defense regulation, including: pad4-1, eds1-1, and NahG, in the presence of the RAC1 allele from Ksk-1. White rust resistance was completely abolished by eds1-1 but was not affected by either pad4-1 or NahG.

Simultaneous Application of Heat, Drought, and Virus to Arabidopsis Plants Reveals Significant Shifts in Signaling Networks

“…RPS6 has been shown to mediate resistance via EDS1 to the P. syringae pv syringae effector HopA1 (Kim et al, 2009). Furthermore, the deduced amino acid sequence of RPS6 shows highest similarity to the Toll/Interleukin-1 receptor (TIR)-NBS-LRR class resistance protein RAC1 that determines resistance to the oomycete pathogen Albugo candida (Borhan et al, 2004;Kim et al, 2009). Probably, RPS6 is an important component against many pathogens.…”

Natural Variation in Small Molecule–Induced TIR-NB-LRR Signaling Induces Root Growth Arrest via EDS1- and PAD4-Complexed R Protein VICTR inArabidopsis

“…TIR-NB-LRR family members can function as immune signaling proteins encoded by R genes responding to specific pathogen effectors in plants (Belkhadir et al, 2004;Chisholm et al, 2006;Jones and Dangl, 2006;Shen and Schulze-Lefert, 2007;Caplan et al, 2008). Compared with characterized R proteins, the predicted VICTR Col protein shows high sequence similarity to that of At1g31540 (64.9% amino acid identity) (Katoh et al, 2002;Thompson et al, 2003;Raghava and Barton, 2006), the Col-0 allele of RAC1 from accession Ksk-1, which mediates PAD4-independent resistance to Albugo candida (Borhan et al, 2004). VICTR Col is in the same cluster of R genes as RPS6 (At5g46470; see Supplemental Figure 4B online) that specifies resistance to the Pseudomonas syringae effector HopA1 (Kim et al, 2009).…”

Natural history of Arabidopsis thaliana and oomycete symbioses

“…1a; Rehmany et al 2000;Borhan et al 2008), and important aspects of compatible interactions including induced accessibility (pathogen-activated defence suppression) and source-sink dynamics affecting carbohydrate metabolism (Chou et al 2000;Holub and Cooper 2004;Tang et al 1996). Only two UK isolates of AcA have thus far been named including the type isolate Acem1 from East Malling, Kent and Acks1 from Keswick, Cumbria (Borhan et al 2004;Holub et al 1995).…”