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How parasites keep the gene pool healthy

22 March 2007

All life forms have depended on having a diverse range of genes in order to adapt and survive through the ages. Research published today in the print edition of Proceedings of the Royal Society B reveals how parasites co-evolve with their hosts so that genetic diversity is maintained. Compromise between hosts and parasites is vital, say scientists at the John Innes Centre.

Researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) have developed a mathematical model to examine how organisms can maintain their gene diversity for resistance to disease. The research highlights how a diverse gene pool helps plants and animals to deal with diseases, and how parasites, in return, use genetic diversity to overcome defences.

“The more diverse, or polymorphic, the organism is, the more it can adapt to its environment. One of the reasons for this genetic diversity is interaction between parasite and host,” comments Professor James Brown.

Despite millions of years of evolution where increasingly improved resistance to disease should be expected, plants and animals including humans are still susceptible to parasites in varying degrees. Aurélien Tellier, a Ph.D. student working with Brown, proposes a general solution to this paradox with their mathematical theory.

Parasites constantly adapt to host organisms, and their hosts constantly evade attack by evolving resistance. But compromise is of the essence, according to Tellier and Brown. They show that when the rate at which the parasite adapts to its host slows down as parasite numbers increase, the genetic diversity in both host and parasite can be maintained. Eventually, the host and parasite arrive at a compromise, where the parasite ceases to become more virulent and the host ceases to become more resistant.

The theory predicts that many biological and ecological factors are likely to contribute to the compromise - for instance when several generations of the parasite survive in the host, or when plant seeds survive several years in the soil without germinating.

“Without these challenging factors in our environment we would most likely have lost genetic diversity a long time ago and become less able to cope with diseases,“ said Brown.

Professor Julia Goodfellow, BBSRC Chief Executive, said: “This research gives us a better understanding of how we have genetically adapted to our environment, and contributes to our knowledge of disease resistance.”

ENDS

Notes to editors

The paper “Stability of Genetic Polymorphism in Host-Parasite Interactions” appears in Thursday’s print publication of Proceedings of the Royal Society B: Biological Sciences. Issue 1611, Vol. 274, pages 809-817.

About John Innes Centre

The JIC, Norwich, UK is an independent, world-leading research centre in plant and microbial sciences with over 800 staff. JIC is based on Norwich Research Park and carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council.

The JIC is internationally renowned for training students and young scientists. Aurélien Tellier is a Ph.D. student from France who chose to study at JIC because it offered him the opportunity to experiment with some highly original ideas at the leading edge of evolutionary biology.

About BBSRC

The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £380 million in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports a number of important industrial stakeholders including the agriculture, food, chemical, healthcare and pharmaceutical sectors. http://www.bbsrc.ac.uk

External contact

Professor James Brown, John Innes Centre

tel: 01603 450615

Andrew Chapple, Press Officer, John Innes Centre

tel: 01603 251490

Contact

Matt Goode, Head of External Relations

tel: 01793 413299
fax: 01793 413382

Tracey Jewitt, Media Officer

tel: 01793 414694
fax: 01793 413382