On the sequencing of the pea aphid genome

By Guest Author 26/02/2010

pea aphid 1

By Dr Peter Dearden*

My group has been involved with genome sequencing since 2004, when we were asked to become involved with the honeybee genome. This week we published our second insect genome, that of the Pea Aphid which was the culmination of 6 years collaborative work with over 200 scientists from 15 countries. The project has cost several million US dollars in sequencing and many more millions spent on researchers’ time. So why should anyone care? Why spend all this time, effort and money on such a tiny insect?

Well, Aphids are important for a number of reasons. Aphids are a key part of natural ecosystems around the world, but are also major pests of agricultural crops. The Pea Aphid and closely related aphids cause millions of dollars in annual crop damage in New Zealand and around the world.

As many aphids are resistant to current insecticides, one of the major aims of the aphid genome project was to try and identify new ways to target these pests. More importantly, as most insecticides are broad range, they unfortunately kill all insects rather than just the target species, so a tailor-made insecticide would protect all the ‘good’ insects.

By understanding the genome, what genes it contains, and what those genes encode, we hope to be able to develop more specific insecticides, thus reducing the environmental and economic impact of pest control.

But the aphid genome is not just important for agriculture. Aphids are remarkable animals that are a key element in an important and understudied group of insects. The genome sequence provides us with important data on this group, thehemimetabolous insects, which enables us to understand the evolution of these creatures. Subsequently, this also throws more light on the already sequenced genomes of honeybees, beetles and flies.

Even more interestingly, aphids can switch between sexual and asexual reproduction; a response which is a result of environmental cues. By understanding the genome, my group is hoping to understand how the environment regulates the genome to produce these different forms of reproduction. By understanding this we hope to better understand how genes interact with the environment in other species, including ourselves.

Aphids can only survive with the help of bacteria that live inside their tissues, and the genome reflects this, as we have discovered that some of these bacterial genes move out of the bacteria and insert themselves in the aphid genome. Along with this comes the finding that the immune system of the aphid is very much reduced compared with other insects, perhaps because they must live with their bacteria.

This enormous effort has been very worthwhile, and I am immensely proud that as a small country we can make a significant contribution to a worldwide research effort. While the aphid genome has told us much about this tiny, but important, insect, and about its place in the tree of life, it also holds vital clues about the fundamental biology of animals; the biology that underlies our very own species.

* Dr Peter Dearden is Director of Genetics Otago Director and Senior Lecturer at the Biochemistry Department of the University of Otago.  He is also Associate Director of the National Centre for Growth and Development (a Centre of Research Exellence)and founder of the Laboratory for Evolution and Development.