Universities win major award to understand how 'hot zones' drive evolution of plant disease

Issue date: 08 January 2013

UWE Bristol has teamed up with the Universities of Oxford and Reading to win a £500,000 grant to study ways of increasing crop yields by reducing disease.

The award from the Biotechnologies and Biological Sciences Research Council (BBSRC) enables researchers to build on recent discoveries about how disease spreads in bean plants. The 3-year project could result in developing new ways to prevent diseases in this valuable food crop.

The principal investigator, Professor Dawn Arnold from UWE's Centre for Research in Biosciences said, “The team has previously discovered that bean plants' natural defences against bacterial infections could be unwittingly driving the evolution of more highly pathogenic bacteria.

“Protecting plants from disease is a major part of national and international food security strategies. This new study will support one of the BBSRC's priority areas of Crop Science. It will be multi-disciplinary, involving aspects of microbiology, pathology, genomics and genetics.

“Our research results will not only help agriculture and policy-makers, but will also be made available to the public.”

Micro-organisms that cause crop disease are engaged in a constant arms race with plants, rapidly evolving to infect previously disease-resistant varieties, or to expand their host range and infect new plant species. The bacterium under study, Pseudomonas syringae, causes an important disease of French bean plants known as halo blight. Symptoms include brown spots surrounded by a yellow halo. The disease causes bean plants to lose their leaves and die, and is a serious and costly problem for farmers worldwide.

When a plant is infected by P. syringae it defends itself by sending a 'suicide signal' to the plant cells surrounding the bacteria. When the affected plant cells die they release antimicrobial compounds toxic to the bacterium.

Dr Helen Neale of UWE, who will be working on the project, said, “In our initial study we demonstrated for the first time that when bacteria are exposed to chemicals produced by disease resistant plants they show an increased ability to take up new DNA from the environment. This allows the bacteria to evolve more quickly than normal, as they gain large numbers of new genes in one go, allowing them to overcome plant disease resistance.”

Dr Gail Preston of the University of Oxford said, “At present there is mounting concern about the emergence of new plant diseases, and the durability of existing sources of disease resistance in trees and crop plants. It seems that the mechanisms by which plants attempt to fight off disease can in fact stimulate pathogens to evolve, contributing to their continued survival, and even promoting the emergence of new strains that are able to infect previously resistant plants.

“In this new project we aim to understand in greater detail how these 'hot zones' drive microbial evolution, by studying their chemical composition, and how signals in the hot zone cause increased DNA uptake in the bacteria. The bacteria we are studying share many common features with other pathogenic bacteria, including those responsible for chestnut bleeding canker and for bacterial canker of kiwi fruit, a disease which is currently threatening kiwi fruit production worldwide. Our results could have broad implications for how we understand plant pathogen evolution, and for how we manage future threats to our forests and crop plants.”

Dr Robert Jackson of the University of Reading said, “This work will provide important insights into how many different pathogens and plant hosts fight each other and therefore will provide other researchers with help in controlling a variety of plant diseases. Importantly, this project provides training for two early career scientists in the area of plant pathology, a key area of expertise that is currently under-represented in the UK.”

Professor Arnold concludes, “Although this work involves plant-bacteria interactions, it has a wider significance in that it could lead to greater understanding of how bacteria evade the immune systems of different hosts including animals and humans.”

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