Activation of a plant nucleotide binding-leucine rich repeat disease resistance protein by a modified self protein

Abstract

Summary Nucleotide binding-leucine rich repeat (NB-LRR) proteins function as intracellular receptors for the detection of pathogens in both plants and animals. Despite their central role in innate immunity, the molecular mechanisms that govern NB-LRR activation are poorly understood. The Arabidopsis NB-LRR protein RPS5 detects the presence of the Pseudomonas syringae effector protein AvrPphB by monitoring the status of the Arabidopsis protein kinase PBS1. AvrPphB is a cysteine protease that targets PBS1 for cleavage at a single site within the activation loop of PBS1. Using a transient expression system in the plant Nicotiana benthamiana and stable transgenic Arabidopsis plants we found that both PBS1 cleavage products are required to activate RPS5 and can do so in the absence of AvrPphB. We also found, however, that the requirement for cleavage of PBS1 could be bypassed simply by inserting five amino acids at the PBS1 cleavage site, which is located at the apex of the activation loop of PBS1. Activation of RPS5 did not require PBS1kinase function, thus RPS5 appears to sense a subtle conformational change in PBS1, rather than cleavage. This finding suggests that NB-LRR proteins may function as fine-tuned sensors of alterations in the structures of effector targets.

Analysis of the ZAR1 Immune Complex Reveals Determinants for Immunity and Molecular Interactions

“…Different domains of NLRs were previously shown to interact with their guarded targets (Collier and Moffett, 2009). The RPS5 NLR guards the PBS1 kinase and triggers resistance when the cysteine protease AvrPphB cleaves PBS1 (Shao et al, 2002(Shao et al, , 2003DeYoung et al, 2012). The CC domain of RPS5 interacts with PBS1, and the LRR domain is required to sense the cleavage of PBS1 by AvrPphB (Ade et al, 2007;Qi et al, 2012).…”

Broadly Conserved Fungal Effector BEC1019 Suppresses Host Cell Death and Enhances Pathogen Virulence in Powdery Mildew of Barley (Hordeum vulgare L.) (Retracted)

“…oryzicola and cultivar-specific HR induced by the AvrPphB effector from Pseudomonas syringae pv. phaseolicola (Ade et al 2007;DeYoung et al 2012;Shao et al 2003). Moreover, homologs of BEC1019 are conserved in more than 90 fungal taxa.…”

Effector Triggered Immunity: NLR Immune Perception and Downstream Defense Responses

“…PBS1 and related kinases are important immune signaling proteins and serve as AvrPphB virulence targets in susceptible genetic backgrounds (Zhang et al, 2010). Interestingly, RPS5 is capable of sensing PBS1 cleavage products as well as PBS1 with a five amino acid alanine insertion located within its cleavage site (DeYoung et al, 2012). Furthermore, the RESISTANCE TO PSEUDOMONAS SYRINGAE A.…”