Tuesday, October 31, 2006

Bee genome

Social insects were my first great scientific enthusiasm, and I still think they're the coolest.

Their behaviour marvellously illustrates the power and subtlety of natural selection. Via kin selection, it can produce altruistic behaviour, but this only works as long as each individual is benefiting — and there is a constant temptation, even for social insects, to choose the selfish path, and rebel against the group.

Honey bees, for example have evolved sophisticated ways to keep selfishness in check, such as worker policing, where workers destroy the eggs laid by fellow workers (but would secretly like to lay eggs themselves).

So, the honey bee genome published in Nature last week is a good thing. But it doesn't tell us much about sociality - when Nature asked project Leader George Weinstock what the most surprising thing about the project was, he replied 'That we did not come up with breakthroughs in understanding social behaviour of the bee'.

Way to hook the public, George. But not really surprising, because the different castes and jobs within a beehive are determined by environment, and developmental factors — queens aren't decided by their genes, but by a diet of royal jelly. What job a worker does depends on its age — they start out as nursemaids, then move outwards, becoming guards, and finally foragers.

So gene regulation is going to be more important than gene content for understanding sociality. Perhaps this is why I found Nature's news and views piece on the genome, by (the great) E. O. Wilson, a tad disappointing — it's more an essay on bees, trotting out a bunch of well-known stuff, than anything that gets to grip with what the genome means.

As well as the Nature paper, it's worth checking out the current Insect Molecular Biology, which has a bunch of freely accessible papers related to the genome.

Besides all the 'how does sociality evolve, and what does it mean for humans' stuff, bees are important, and threatened, providers of ecosystem services. When the genome was completed last year, I had a piece in the Financial Times about this; I'm putting up the director's cut below.

Until last week, I didn't know that bumble bees were also commerically traded and transported, and that this similarly helped to spread disease. Then I saw this paper in the current issue of Population Ecology.

Anyway, here's the FT piece. Science made cool also posted on this issue recently.

A plague has swept the world. Thousands of communities have been infected and wiped out. We are trying to fight back with chemicals and quarantine, but it's a rearguard action, and the threat of a new epidemic is always lurking.

But this isn't Sars or Aids. The victims are honeybees. Across the world, beekeepers are battling with a menagerie of parasites and diseases, trying to stay one step ahead of existing threats, while remaining alert for new scourges.

The honeybee genome recently completed by a team of US scientists gives bees' human allies a powerful tool. It's the first complete genome of any domesticated animal; for thousands of years we have selected bees for docile temperaments and high honey production. Now, scientists can look for the genes that will help bees fight off their ailments.

"I'm optimistic that we'll be able to breed bees resistant to a variety of diseases," says Jay Evans, a geneticist at the US Department of Agriculture's Bee Research Laboratory in Beltsville, Maryland. Dr Evans works on the bees' immune system, and is seeking ways to boost its power. He is also developing tools to diagnose sick bees, by looking for genes that are switched on when insects are sick or starving.

There's more at stake than just the sweet stuff on your breakfast toast. In the UK alone, bees' pollination of crops is estimated to be worth about £200 million - ten times the value of the honey they produce. Fewer bees would mean more expensive food. And the insects perform an unmeasurable service to our environment by pollinating wild plants.

Bees' most serious enemy is a millimetre-long mite called Varroa destructor. The mites suck the blood of adult and larval bees and transmit deadly viral infections. Without treatment, an infested hive is doomed. Beekeepers can control varroa with pesticides, but the mites are starting to evolve resistance.

Varroa originally lived in peaceful coesixtence with a far-eastern bee species. But a century ago it switched to western honeybees. Since then, varroa has spread around the world, reaching the US in 1987 and the UK in 1992, where more than 5,000 hives have been infected. The impact on wild bees has been devastating: "In Europe and North America there are virtually no wild honeybees left," says Dr Evans.

Bees have millions of years of experience of coping with diseases. But we have made them vulnerable, by moving bees around, bringing diseases into contact with hives that have no resistance to them, in the same way that Europeans exported smallpox to the New World. "The movement of bees has increased tremendously, and there's always a risk that you'll introduce an exotic parasite with an exotic virus," says Brenda Ball, who studies varroa at the Rothamsted Research Institute in Hertfordshire.

Rather than create GM bees, researchers will most likely use the genome to steer breeding programmes. The genes that control behaviour could be the key to producing parasite-proof honeybees, says Dr Ball. We know that some bees are more hygenic than others, in their ability to detect and destroy infected larvae, for example. The genome should help us find out how this is determined, and breed more vigilant animals. It could also help us work out how Asian bees are able to resist varroa.

The varroa mite might be beekeepers' worst nightmare, but it's far from the only one. In December the European Commission restricted bee imports, in a bid to keep out two other damaging parasites, a beetle and another mite. And the insects are also prey to a range of fungal and bacterial diseases.

Bees are vulnerable to disease for the same reasons that we are - they live in dense groups, where individuals are in constant contact. Such cities support pathogens and give them the chance to spread. This makes them good models for understanding human disease, and researchers are already testing bees' natural antibiotics to see if they could work against our own infections.

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