The Guttman and Desveaux labs in Cell & Systems Biology have published a comprehensive analysis of the huge variety of methods used by bacteria to evade the immune system of plants in the latest issue of Science magazine: “The pan-genome effector-triggered immunity landscape of a host-pathogen interaction.”

Imagine you’re growing a tomato plant and you see black spots on the leaves and fruit. This could be a bacterial infection. You notice that a weed that’s growing beside it in your garden doesn’t have the black spots even though it’s touching the infected areas. This is due to resistance genes (R-genes) in wild plants that give it immunity to infection by the black spot bacteria.

Professors Desveaux and Guttman’s goal was to survey all the different ways that one species of bacteria can try to evade the immune response in plants. Working with post-doc Dr Marcus Dillon and graduate students Bradley Laflamme, Alex Martel and Renan Almeida, they collected together over 500 different effectors used to infect plants from all variants of the bacterial species Pseudomonas syringae. By exposing the wild plant Arabidopsis thaliana to this comprehensive library, they identified all the R-genes that are stimulated by these effectors, including two new ones.

Although crop plants like tomatoes have resistance to many infections, they may have lost some R-genes through breeding programs that selected for traits desired by humans. Those R-genes may still be active in wild or heirloom varieties of the plant. To apply the discoveries made in their Science paper, the Guttman and Desveaux labs have received funding from the Weston Foundation Seeding Food Innovation program to identify and reintroduce missing R-genes into crop plants.

More details on these tools for combating crop diseases are shared in this UofT News story