Pseudomonas syringae Effector AvrPphB Suppresses AvrB-Induced Activation of RPM1 but Not AvrRpm1-Induced Activation

Abstract

The Pseudomonas syringae effector AvrB triggers a hypersensitive resistance response in Arabidopsis and soybean plants expressing the disease resistance (R) proteins RPM1 and Rpg1b, respectively. In Arabidopsis, AvrB induces RPM1-interacting protein kinase (RIPK) to phosphorylate a disease regulator known as RIN4, which subsequently activates RPM1-mediated defenses. Here, we show that AvrPphB can suppress activation of RPM1 by AvrB and this suppression is correlated with the cleavage of RIPK by AvrPphB. Significantly, AvrPphB does not suppress activation of RPM1 by AvrRpm1, suggesting that RIPK is not required for AvrRpm1-induced modification of RIN4. This observation indicates that AvrB and AvrRpm1 recognition is mediated by different mechanisms in Arabidopsis, despite their recognition being determined by a single R protein. Moreover, AvrB recognition but not AvrRpm1 recognition is suppressed by AvrPphB in soybean, suggesting that AvrB recognition requires a similar molecular mechanism in soybean and Arabidopsis. In support of this, we found that phosphodeficient mutations in the soybean GmRIN4a and GmRIN4b proteins are sufficient to block Rpg1b-mediated hypersensitive response in transient assays in Nicotiana glutinosa. Taken together, our results indicate that AvrB and AvrPphB target a conserved defense signaling pathway in Arabidopsis and soybean that includes RIPK and RIN4.

Behind the lines–actions of bacterial type III effector proteins in plant cells

“…2003) (see below). AvrPphB also cleaves the kinase RIPK (RPM1-induced protein kinase), which is required for the phosphorylation of the immune regulator RIN4 (Russell, Ashfield and Innes 2015) (see below).…”

“…2011). RIPK is also targeted by the cysteine protease AvrPphB from P. syringae , which cleaves RIPK (Russell, Ashfield and Innes 2015). Notably, AvrPphB suppresses the AvrB- but not the AvrRpm1-mediated activation of RPM1, suggesting that RIPK is dispensable for the RPM1-dependent recognition of AvrRpm1 (Liu et al .…”

“…Notably, AvrPphB suppresses the AvrB- but not the AvrRpm1-mediated activation of RPM1, suggesting that RIPK is dispensable for the RPM1-dependent recognition of AvrRpm1 (Liu et al . 2011; Russell, Ashfield and Innes 2015). AvrB does not only target RIPK but also interacts with MPK4, which is an additional RIN4 interaction partner (see above).…”

Resistance of Bacteria to the Factors of the Innate Immune System, Mediated by Bacterial Proteases

“…On the example of macrophages-this leads to a loss of ability to phagocytize bacteria. Similarly, the intracellular GTPase and serine/threonine kinases in plant cells have the bacterial enzyme AvrPphB peptidase (family C58.002, clan CA) isolated from Pseudomonas syringae [69,70]. In contrast to the enzymes described above, which are introduced directly through the membrane into the host cell, the toxin from Bacillus anthracis enters the cell only with endocytosis, after which it moves from the endosomes to the cytoplasm and its metalloproteinase component, related to the lethal toxin cleaves the MKK kinases, thereby effectively blocking the activation of a genes, dependent on the NF-kB factor [71].…”

Characterization of The Interaction Between RIN13 (RPM1-Interacting13) and Sumo Proteins in Arabidopsis Thaliana

“…This protein is termed RIN13 (RPM1-Interacting Protein13) and was suggested to function as a positive regulator of RPM1 (Resistance to P. syringae PV maculicola 1). RPM1 belongs to the family of R (Resistance) protein, specialized in conferring immune response to avirulence (avr) protein of Pseudomonas malicola (Ashfield et al, 2014;Russell, Ashfield, & Innes, 2015)the Pseudomonas syringae effector proteins AvrB and AvrRpm1 are both detected by the RESISTANCE TO PSEUDOMONAS MACULI-COLA1 (RPM1. The avr protein effectors (especially AvrRpm1) entered the host plants through type III secretion system (TTSS) and activated resistance pathways.…”