Protecting against the oomycete threat Oomycetes cause serious disease in ecosystems, agriculture and aquaculture, and represent a major threat to food security. Researchers in the PROTECTA project are investigating how oomycetes interact with their hosts while also looking to apply this knowledge to improve plant and crop resilience, as Professor Laura Grenville-Briggs and PhD student Christian Andersen explain. A group of eukaryotic microbes, oomycetes were historically thought to be fungi, but now are recognised as being more closely related to brown algae. From an evolutionary perspective, oomycetes arose as pathogens of marine algae before evolving to interact with land plants and animals, and certain species can cause serious disease. “For example, an oomycete called Aphanomyces euteiches is a pathogen of legume plants, like peas and beans. It causes major problems when present in the soil as essentially you can’t grow peas for around 8-10 years, and there are no fully resistant varieties,” says Laura Grenville-Briggs, Professor of Integrated Plant Protection at the Swedish University of Agricultural Sciences (SLU). Another type of oomcyete called Phytophthora infestans causes potato late blight, a disease which was a factor in the Irish potato famine and remains an issue today. “It’s a big problem for potato growers here in Sweden, as growers typically have to spray fungicides weekly throughout the growing season,” explains Professor GrenvilleBriggs. “More durable resistance, and biological control options will reduce our reliance on synthetic (chemical) fungicides, which will be welcomed by both farmers and the wider society as a move to make potato production more environmentally sustainable.”
PROTECTA project As the lead of the PROTECTA project, Professor Grenville-Briggs is both pursuing fundamental research into different species of oomycetes and also looking to apply this knowledge to improve plant protection. The project is an ITN training programme in which 15 Early-Stage Researchers (ESRs) are conducting research into oomycetes affecting various plants, crops and animals,
Sugar beet tap roots that have a natural infection of the oomycete Aphanomyces cochlioides.
and Professor Grenville-Briggs believes it’s important to share ideas across different sectors. “These different sectors are facing similar problems, and we can learn a lot by comparing approaches. Learning about something that’s being done in a particular sector may stimulate innovation in another,” she says. Researchers in the forestry sector are typically quite advanced in their ecological understanding in comparison to those in agriculture for example, while Professor Grenville-Briggs says valuable insights can also be drawn from the aquaculture sector. “In aquaculture researchers are often highly advanced in immunology and the identification of antibodies. There are sort of analogues to antibodies that we could potentially use in agricultural settings,” she outlines. The ESRs in the project are conducting research into a variety of different oomycetes, with a lot of attention focused on effector proteins. Some of these effector proteins can manipulate the host and help pathogenic oomycetes cause infection. “In P. infestans for example, there could be as many as 400 different effector proteins with different roles, and they may come into play in different environmental conditions,” explains Professor Grenville-Briggs. These effector proteins effectively infiltrate the cells of a host plant
when an infection occurs, and prevent its normal immune response. “They interfere in molecular, plant-based signalling, and they effectively stop signals being sent to other parts of the plant,” says Professor Grenville-Briggs. “The plant will respond by trying to make the cell as toxic as possible – it will sacrifice individual cells which are under attack, in a leaf or a stem or a root, to try and preserve the health of the whole plant. The effectors then try to stop that process. So, there’s a kind of arms race that goes on between the plant – or fish – and the pathogen.” This topic is at the heart of the project’s overall agenda, with some ESRs quantifying specific effector proteins, some characterising specific responses of the host plant, or fish, to effectors, while others are looking at the ecology. Based at SLU, Christian Andersen’s PhD project sits somewhere between ecology and molecular biology. “I’m researching how an oomycete called Pythium oligandrum uses these effector proteins. What is the role of these effectors when P. oligandrum parasitises other oomycetes in agriculture?” he says. This particular oomycete can be used to help strengthen a plant’s defences against infection, and can directly kill plant pathogenic oomycetes and fungi, so now researchers are exploring the potential of using P. oligandrum as a biological control agent against crop pathogens. “I will spend some time at a sugar beet breeding company, DLF Beet Seed, where I will try to help them combat one of the major diseases which affects sugar beet, using this biological control agent P. oligandrum,” continues Andersen. “The initial idea is to coat the seed in the spore solution of P. oligandrum, and then it will hopefully colonise the plant root and provide enhanced protection against the disease.”
A field trial carried out by ESR Murilo Sandroni to evaluate resistance to potato late blight under future climate scenarios (high atmospheric CO2) at the EPPN research station, Julich, Germany July 2021.
Salmon eggs infected with Saprolegniosis caused by a species of Saprolegnia.
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