Dissecting PBR1-mediated recognition of AvrPphB protease activity in barley (presented at the 2023 IS-MPMI meeting)

We previously identified a barley NLR gene, AvrPphB Response 1 (Pbr1), whose protein product confers recognition of the Pseudomonas syringae effector protease AvrPphB. In Arabidopsis, recognition of AvrPphB occurs through proteolytic cleavage of PBS1 that then activates the immune receptor RPS5. Though both Arabidopsis and barley have evolved a system for recognizing AvrPphB, it is unclear which barley receptor-like cytoplasmic kinases are responsible for activating PBR1- dependent immune responses. Here, we generated decoy versions of several barley PBS1-like proteins that could be cleaved by the TuMV NIa protease, with the expectation that proteolytic cleavage of the barley decoy proteins would activate PBR1. Our results revealed that proteolytic cleavage of multiple barley PBS1-like proteins activate PBR1-dependent immune responses. We also show that cleavage of barley PBS1-like orthologs from wheat, rice, maize, and sorghum also activate PBR1, revealing PBR1 can detect cleavage of PBS1-like proteins from other monocot crop plant species. Collectively, our results suggest PBL-based decoys may be used to expand the effector recognition specificity of PBR1.

This work was presented as a poster at the 2023 IS-MPMI meeting in Providence, RI