Fly will steal the show

Steve Farrar looks at research sure to grab the limelight at the American Association for the Advancement of Science meeting next week.

The tiny brown fruit fly is seldom welcomed, often ignored. Usually, the most attention it can hope to attract is an ineffectual swipe of the hand as it hovers around the fruit bowl. But for more than 80 years, this seemingly insignificant insect has held a special place in the hearts of scientists. In fact, the humble Drosophila is something of a celebrity - no fewer than three Nobel prizes have been awarded for research principally based on understanding aspects of its genetics.

But its finest hour is yet to come. In a month's time, a group of United States scientists will publish its decoded genome, the genetic instruction manual that contains all the information needed to construct and operate Drosophila melanogaster.

This will make it the most complex organism to be decoded in this fashion, the precursor to the human genome that will follow soon afterwards. In fact, its significance is more profound than that: much of the basic chemistry of the fruit fly is also to be found in humans so the Drosophila genome will be a standard guide to complex lifeforms. The human genome, at 20 to 30 times the length, will be the deluxe version.

Gerald Rubin, Howard Hughes professor of genetics and development at the University of California, Berkeley, has been working towards this goal with the Berkeley Drosophila Genome Project since 1992.

"Once nature solved a problem in evolution, it tended to use the same solution over and over again," he said. "So the genes that helped a fruit fly to remember something or to have a circadian rhythm or whatever - the same or similar genes probably exist in humans to do the same function."

Discover the function of an important Drosophila gene and you gain a good idea of what the corresponding human gene, if it exists, does. Then you gain an insight into a vast range of questions from how a human embryo develops to how some forms of cancer might proliferate. So scientists have long experimented on generations of fruit flies for what they can tell us about ourselves.

In addition, it is a simple matter to mutate a fruit fly so that a particular gene is ruined in a bid to discover its function. Such an experiment would be impossible to repeat in humans, but animal rights protesters seem to lose their enthusiasm for opposing experimentation when it comes to insects.

Even a cursory glance at the programme for next week's meeting of the American Association for the Advancement of Science, in Washington DC, reveals the importance and anticipation of decoding the human genome. From understanding how the brain works to developing new pharmaceuticals, that magic phrase crops up again and again across so many disciplines. Yet Drosophila will be absolutely central to these various efforts.

At the meeting, Professor Rubin, together with Edward Lewis, the Caltech biologist who received the 1995 Nobel prize in medicine for his work on the genetic control of early embryonic development, and two experts from Craig Venter's sequencing company, Celera Genomics, will outline their work on the Drosophila genome to date and enthuse about the benefits that might flow from it.

Celera, which struck a deal with Rubin a year ago in a bid to test-run some of its latest sequencing techniques, has already signed a deal with the pharmaceutical giant Pfizer that includes full access to this information. Never before will a humble insect have received such high praise.

The collection of raw sequencing data was completed in September - 18 months ahead of schedule thanks to Celera's technology - since when sophisticated computer techniques have been used to assemble the complete genome, short of maybe 1 or 2 per cent.

Scientists around the world will then be able to devour the data, identify genes and make further inroads in the quest to reveal how much DNA influences our lives.

Rubin's own laboratory aims to use this information to boost work on how cells read, integrate and interpret the information they receive from their neighbours. In addition, the Californian team is investigating how the genome is organised at its most fundamental level.

Many institutions and university departments in the United Kingdom have long been studying genetics with the help of the fruit fly. In the department of genetics at Cambridge University, Michael Ashburner, professor of genetics, and colleagues from the University of Dundee are setting up one of the most advanced facilities for the study of Drosophila genes.

He is effusive about the imminent announcement. "This is a quite extraordinary event in biology, since this little fly is the model organism par excellence for the experimental study of biological phenomena and processes. It is already clear that Drosophila is by far the best model for the study of gene function in mammals, including humans," he said.

However, he notes that this is "only the end of the beginning".

To unlock the potential in the genome, the scientists will have to reveal not only a gene's function - the protein it creates - but also how it interacts with the products of other genes and how this comes together to orchestrate the complex processes of the fly.

This will be no mean feat - Drosophila's importance is assured for years to come.