How generalist parasites with wide host ranges evolve is a central question in parasite evolution. Parasites adapt in response to their host organisms' defences and in many cases this adaptation is specific to a particular host species.

A. candida is a plant pathogen and could be easily confused with a fungus despite being very distantly related to fungi. The plant parasite can grow on diverse plants of the cabbage family, including vegetable crops and common weeds.

The project (“Albugon”) was led by Prof Jonathan Jones at The Sainsbury Lab (TSL), Norwich, who won a five-year Advanced Investigator Grant from the European Research Council to fund the work. A team of scientists at TSL, including Mark McMullan, now of The Genome Analysis Centre (TGAC), set out to use genome sequencing to identify the important differences between A. candida races that infect different weeds and crops.

The research showed that isolates of the parasite that infect different plants carry distinct gene repertoires, but nevertheless carry shared segments of the genome, indicating recent and continuing gene exchange between races that grow on different hosts. This suggests parasite races that infect crop species may be regularly receiving infusions of genetic variation from races that infect weeds.

“We were puzzled that distinct races of Albugo show evidence of genetic exchange, even though they grow on different host species," said Prof. Jonathan Jones. “However, we then realised that this could be explained by the extraordinary capacity of Albugo to shut down host defences. Put simply, we believe Albugo suppresses immunity of host plants so that it can have sex”.

“Interactions and evolution of plants and microbes is fundamental to agriculture and global food security. Due to the advances in genomics, it is now feasible to look at very many genomes within a wild species,” said Dr Mark McMullan, Population & Evolutionary Biologist in the Plant & Microbial Genomics Group at TGAC and first author of the study.

“This has opened the door for scientists to conduct their genome analyses using population genetic techniques, a combination of advanced methods that began development long before the discovery of the structure of DNA. The application of these methods will further advance our understanding of evolution of plant pathogens.”

Previously in the Jonathan Jones’ group at TSL, Mark McMullan continued his work on the project at TGAC in collaboration with population biologist Cock van Oosterhout at UEA. The scientific paper “Evidence for suppression of immunity as a driver for genomic introgressions and host range expansion in races of Albugo candida, a generalist parasite” is now published in eLife.

Background

white rust is a disease in plants caused by the oomycete Albugo candida or one of its close relatives. Plants susceptible to this disease generally include members of the Brassica family.

Brassica is a genus of plants in the mustard family (Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plant.

About TGAC

The Genome Analysis Centre (TGAC) is a world-class research institute focusing on the development of genomics and computational biology. TGAC is based within the Norwich Research Park and receives strategic funding from the Biotechnology and Biological Science Research Council (BBSRC) - £7.4M in 2013/14 - as well as support from other research funders. TGAC is one of eight institutes that receive strategic funding from BBSRC. TGAC operates a National Capability to promote the application of genomics and bioinformatics to advance bioscience research and innovation.

TGAC offers state of the art DNA sequencing facility, unique by its operation of multiple complementary technologies for data generation. The Institute is a UK hub for innovative Bioinformatics through research, analysis and interpretation of multiple, complex data sets. It hosts one of the largest computing hardware facilities dedicated to life science research in Europe. It is also actively involved in developing novel platforms to provide access to computational tools and processing capacity for multiple academic and industrial users and promoting applications of computational Bioscience. Additionally, the Institute offers a Training programme through courses and workshops, and an Outreach programme targeting schools, teachers and the general public through dialogue and science communication activities. www.tgac.ac.uk

About The Sainsbury Laboratory (TSL www.tsl.ac.uk)

The Sainsbury Laboratory (TSL) in Norwich is a world-leading research centre focusing on making fundamental discoveries about plants and how they interact with microbes. TSL not only provides fundamental biological insights into plant-pathogen interactions, but is also delivering novel, genomics-based, solutions which will significantly reduce losses from major diseases of food crops, especially in developing countries. TSL is an independent charitable company and receives strategic funding from the Gatsby foundation with the balance coming from competitive grants and contracts from a range of public and private bodies, including the European Union (EU), Biotechnology and Biological Sciences Research Council (BBSRC) and commercial and charitable organisations.

About BBSRC

The Biotechnology and Biological Sciences Research Council (BBSRC) invests in world-class bioscience research and training on behalf of the UK public. Its aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.

Funded by Government, and with an annual budget of around £467m (2012-2013), it supports research and training in universities and strategically funded institutes. BBSRC research and the people it funds are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Research investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.

For more information about BBSRC, our science and our impact: http://www.bbsrc.ac.uk
For more information about BBSRC strategically funded institutes: http://www.bbsrc.ac.uk/institutes

About ERC

The main goal of the European Research Council (ERC) is to encourage high quality research in Europe through competitive funding. For more information see http://erc.europa.eu