Science 351, 684–687 (2016)

To fight off infection, an organism must first recognize that it is under attack. Plants have a variety of mechanisms — that are often pathogen-specific — to identify invaders. Working at Indiana University, USA, Kim et al. have demonstrated how to change the specificity of a pathogen detection system so that plants can be made alert to new diseases.

One of the pathogen recognition systems in Arabidopsis involves RPS5, a nucleotide-binding leucine-rich repeat protein that indirectly provides resistance to the bacterium Pseudomonas syringae. Under normal circumstances, the kinase PBS1 represses RPS5, preventing a resistance response. However, PBS1 contains a sequence of amino acids that is targeted by a photolytic enzyme produced by P. syringae; so, in the presence of the pathogen, PBS1 is cleaved and deactivated, thereby allowing RPS5 to mount a defence response.

Kim et al. transgenically modified Arabidopsis plants so that their PBS1 proteins contained the target site for a protease from turnip mosaic virus (TuMV) instead of the P. syringae-sensitive sequence. When infected with TuMV, these transgenic plants displayed a type of resistance known as ‘trailing necrosis’, and also showed lower levels of virus accumulation than wild-type plants.

Redirecting the focus of a plant's defence systems in this way could provide an approach to swiftly proofing crops against newly emerging diseases.