What did viruses ever do for us? The evolution of “good” viruses

Professor John Carr - President of the Cambridge Philosophical Society

• Monday 9 November 2026, 17:30 – 18:30
• Bristol-Myers Squibb Lecture Theatre, Cambridge

Upcoming event Booking Recommended In-person Lecture Michaelmas Term

• Event cost: Free
• Disabled access?: Yes
• Booking required: No

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Overview

Viruses generally get a very bad press. Deservedly so. Viruses cause serious epidemics and pandemics in humans and threaten food security by causing crop and livestock diseases. However, of the more than 10³⁰ virus particles that exist at any instant, few endanger us, plants, or animals. Most infect bacteria and archaea and without these viruses Earth’s biosphere would collapse.

Viruses are the largest group of emerging plant pathogens. But paradoxically, many confer benefits on plants that may increase survival and reproductive success. These apparently mutualistic effects may be conditional, for example, by aiding host survival under conditions of drought or cold or, more surprisingly, by helping plants attract pollinators.

Certain viruses, notably ‘partitiviruses’ and ‘endornaviruses’ may have travelled so far on an evolutionary path as to become obligate plant symbionts. These viruses are transmitted exclusively via seed and pollen and are not infectious in a conventional sense (i.e., not transmitted by invertebrates, wounding etc.), and induce no obvious disease. It has been suggested that these ‘persistent’ viruses are mutualists and might be useful in crop breeding. Recent experiments exploring these ideas will be discussed.

Speaker Biographies

John Carr is Professor of Plant Virology at Cambridge University's Department of Plant Sciences. His research interests include viral subversion of plant resistance, viral gene expression, plant-virus-insect vector interactions, the effects of virus infection on interactions of plants with beneficial insects such as pollinators, and the occasional mutualistic effects of viruses on their hosts. He has also done work on resistance against bacterial and fungal plant pathogens. Over the years Professor Carr has also collaborated on practical aspects of plant virology with colleagues in eastern, central and western Africa, particularly on insect-vectored viruses.

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