Research, led by the University of Warwick, The Sainsbury Laboratory, and Virginia Polytechnic Institute and State University (Virginia Tech), has sequenced the genome of a plant disease causing organism revealing that it acts like a "stealth bomber of plant pathogens". The research has uncovered the tactics used to sneak past the plant's immune defences. That same discovery also provides tools for researchers to identify the components of the plant immune system and devise new ways to prevent disease.
The research at the University of Warwick, the Sainsbury Laboratory and Virginia Tech, was funded by the UK's Biotechnology and Biological Sciences Research Council (BBSRC), The Gatsby Charitable Foundation, NSF, and the U.S. Department of Agriculture. It looked at an obligate biotroph, a type of plant pathogen which has adapted so exquisitely to its host that it extracts nutrients only from living plant tissue and cannot grow away for their plant. While the organism may once have been able to exist by itself it has now evolved in such a way that it cannot survive without a host plant and usually that has to be a very specific type of host plant.
The researchers looked specifically at Hyaloperonospora arabidopsidis, that can only survive on its host the model plant Arabidopsidis, the model plant of the plant science world. Hyaloperonospora arabidopsis is a type of water mould that causes yellow patches and fuzzy white mould on the leaves. Close relatives cause disease and damage on many crops including broccoli, maize, grapes and lettuce. The researchers found that this particular plant pathogen has evolved a highly successful strategy that allows it to present a very small profile to its host plant disease prevention defences. By losing, or never acquiring in the first place, many abilities found in other pathogens, Hyaloperonospora arabidopsidis is able to minimise the number of genetic markers it carries that could be picked up by a plant's defences and seen as a threat.
The lead researcher from the University of Warwick's School of Life Sciences Professor Beynon said:
"Hyaloperonospora arabidopsidis is one of the stealth bombers of the world of plant pathogens. We can see much of how it has actually slimmed down some key elements of its genetic material in order to get around the plant's natural defences - essentially by stealth."
One of the key ways the University of Warwick, Sainsbury Laboratory and Virginia Tech researchers will exploit this plant pathogen's arsenal to mount their own sneak assault on many much other challenging plant pathogens is through the "RXLR effectors". Such pathogens use a large armoury of "RXLR effectors" to suppress the mechanisms used by plants to detect and then block pathogens. Although having a slimmed down stealth profile Hyaloperonospora arabidopsidis still maintains an amazing 134 RXLR effectors in its armoury. Understanding the role of these effectors will be the key direction of future research in the field.
This parsimonious approach may help Hyaloperonospora arabidopsidis in its stealth attack but it also opens up a major opportunity for researchers to gain insights across a vast range of plant pathogens. Not only does Hyaloperonospora arabidopsidis infect the ideal plant model (Arabidopsis) used by plant researchers the world over for decades it also attacks that model plant with a bare bones set of weapons that greatly simplifies a researcher's task in unpicking how those weapons work. Any insights gained can then be directly applied to the understanding of how those same weapons work in much more complicated pathogens.
Professor Beynon also said:
"This research provides a new window into how Hyaloperonospora arabidopsidis has slimmed down key elements of its genetic material to avoid the plant's natural defences. Despite this reduction, amazingly, it still sends over 100 proteins into plant cells to suppress the immune responses. Understanding how these proteins suppress plant immunity will enable us to select disease resistant crop plants and combat plant disease such as potato blight and sudden oak death."
"Losses to disease in food crops can be very significant and to feed a growing population set to reach 9 billion by 2050 we need to increase food production. Reducing losses because of disease will be an important part of this."
|Contact: Jim Beynon|
University of Warwick