University of Dundee

Late blight pathogen actually boosts potato growth to switch off immunity

16 May 2017

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: “There are communication signals between growth and immunity systems in plants, allowing the plant to direct resources where they are needed most.

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

“This discovery reveals a novel strategy the pathogen uses to suppress the plants immune system, highlighting a vulnerability in our crops that we could potentially target in the future to help protect them from disease.”

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 plants may open further avenues to research crop pests and diseases responsible for enormous global food crop losses each year.

Image: Transgenic potato cv Desiree lines expressing 35S:AVR2 show morphological hallmarks of an overactive. Leaf phenotype of 35S:AVR2 plants showing reduced compound formation and loss of symmetry. (Figure 1B,  Turnbull et al. Plant Physiol. 2017;174:356-369).

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.