Late blight pathogen boosts potato growth to switch off immunity

“This discovery reveals a novel strategy that can be used by a pathogen to suppress the plants immune system, highlighting a vulnerability in our crops that could potentially be protected in the future.”

Scientists at the James Hutton Institute, in collaboration with the Division of Plant Sciences at the University of Dundee and the Fujian Agricultural and Forestry University of China, have discovered that the pathogen responsible for the devastating crop disease potato late blight manipulates the plants’ growth and development to boost its infection process.

Late blight played a major role in the historical Irish potato famine, and is still a huge problem for farmers today; causing massive crop losses and proving difficult to manage by chemical control and traditional breeding methods.

The fungal-like pathogen, Phytophthora infestans, secretes a protein into the plant called AVR2, which targets the plants’ mechanisms responsible for normal growth and development. This protein, or ‘effector’, can have an impact on the plants’ growth and immune response, allowing infection to spread further through the plant.

Dr Eleanor Gilroy, a molecular plant pathologist at the James Hutton Institute and co-author of the study, said: “Natural crosstalk exists between growth and immunity in plants, allowing the plant to use resources where they are needed most.

“The late blight pathogen has evolved to exploit this, tipping the balance in favour of growth so that disease can progress while the plants defences are low.

“This discovery reveals a novel strategy that can be used by a pathogen to suppress the plants immune system, highlighting a vulnerability in our crops that could potentially be protected in the future.”

The role of effectors like AVR2 is not yet fully understood by scientists. Pathogens secrete them into plants during infection, and the interaction between effectors and pathogens may open further avenues to research crop pests and diseases responsible for enormous global food crop losses each year.

Paper: Dionne Turnbull et al. RXLR effector AVR2 up-regulates a brassinosteroid-responsive bHLH transcription factor to suppress immunity, Plant Physiol. 2017 174:356-369.