University of Rochester

Rochester Biologists Make Science's Top 10 Breakthroughs of 2006

February 7, 2007

The journal Science has released its top ten breakthroughs of 2006, and two University of Rochester biology projects on evolution made the list at number seven.

Science's seventh most impressive science breakthrough entry for the year says: It doesn't take much to send an organism down speciation's path. Several studies these past 12 months have uncovered genetic changes that nudge a group of individuals toward becoming a separate species by giving them an edge in a new environment. The year's results speak to the power of genomics in helping evolutionary biologists understand one of biology's most fundamental questions: how biodiversity comes about.

H. Allen Orr, along with graduate student J. P. Masly, were cited for their September Science paper on how gene transposition can cause sterility in hybrids between certain fruit fly species, and Daven Presgraves was noted for his research in Molecular Biology and Evolution to a similar gene that causes hybrid lethality and promotes speciation.

Masly and Orr discovered that an old and relatively unpopular theory about how a single species can split in two turns out to be accurate after all, and acting in nature. Their paper reveals that scientists must reassess the process involved in the origin of species since speciation may be triggered by genes that change their locations in a genome.

The team found that the absence of a certain gene, called JYAlpha, could cause sterility in the hybrids of two species of fly because the gene, which is pivotal for fertility, has changed its location in the genome. The result is that some hybrid male offspring are sterile because they'd receive no copy of this gene at all. Importantly, JYAlpha is one of the same genes that is essential for sperm motility in humans and other mammals as well.

Orr and Masly's work shows a back door through which speciation can start. If the right genes jump around in the genome, a population can begin creating individuals that can't successfully reproduce with the general population. If other speciation pressures, like geographic isolation, are added to the mix, the pressure may be enough to split one species into two new species.

Presgraves authored the second paper recognized by the journal Science. In his paper he also looked at hybrid incompatibility in fruit flies, but with an eye toward how the gene Nup96 changed its function over the generations. His paper appeared in October in the journal Molecular Biology and Evolution.

Presgraves outlined how evolution drove the gene to have different functions in two different, but closely related species of fruit fly. In studying five proteins that interact with Nup96, he found that all five had adapted to evolutionary pressures in different ways. The fact that each of these genes showed evidence for adaptive evolution came as a surprise, suggesting that the bouts of adaptation the genes experienced did not happen independently, but rather reflected a shared history of evolution.

Presgraves suggests it's possible that the two species of fly inherited a genetic "conflict" from their mutual ancestor, and essentially took different genetic paths to resolve the conflict. By taking different genetic paths, the two nascent species were no longer reproductively compatible, and thus they were forced to continue to evolve into two completely separate species.

The complete list of Science's top ten science breakthroughs of 2006 can be read here