Combating plant disease outbreaks by preventing pathogen evolution may help protect food crops

One component of food security is to try and improve crop yields to produce more food, more consistently, by reducing the impact of disease. Diseases are caused by a variety of pathogens and one of our major strategies for preventing disease outbreaks is the employment of resistant varieties of plants – these are plants that sense the presence of pathogen molecules (“flags”) through naturally-occurring surveillance systems and can then rapidly react to arrest infection. This process can vary from strengthening the plant cells, making them harder to penetrate, to production of a variety of antimicrobial chemicals that act to kill the bacteria, through to “hari-kiri” suicide of plant cells to quarantine the pathogen to the site of infection and prevent further spread in the plant. This torrent of plant activity results in an anti-microbial “hot zone”, but the success of the plants immune system in acting to stop pathogen infection can also be its downfall – because the pathogens can rapidly adapt by evolution to overcome the plants immune system, and they seem to do it due to the plants immune reaction. The pathogen can do this by either turning off genes to hide the “flags” or just by entirely ejecting the genes so that they don’t “flag” themselves up anymore. To better understand how the pathogen adapts to the plant “hot zones”, Robert Jackson (School of Biological Sciences), Dawn Arnold (UWE, Bristol) and Gail Preston (Oxford) were recently awarded over £550k by the BBSRC to employ two research assistants to work on this. The aim is to identify the plant compounds produced during an immune response and to pinpoint which ones are the triggers for bacteria to turn off their “flags”. The way in which the pathogen senses and responds to the plant “hot zone” compounds will also be studied. By combining these approaches, it is hoped that our knowledge of pathogen evolution and plant immunity will be improved. In turn, it may be possible to breed plants that maintain disease resistance but make less of the compounds that trigger pathogen evolution. And hopefully this will help to improve disease resistance and reduce crop losses to increase food supplies to future generations.