A UR professor and a graduate student have been working on a study involving evolutionary genetics and fruit flies, concluding that a rapidly evolving gene in a fruit fly has caused the creation of a new species.

UR Professor of Biology Daven Presgraves, Grass Fellow at the Radcliffe Institute for Advanced Study at Harvard University, along with UR graduate student Shanwu Tang, recently published a study, entitled ‘Evolution of the Drosophila Nuclear Pore Complex Results in Multiple Hybrid Incompatibilities,” in Science Magazine. The paper describes a newly found gene that leads to the formation of a new species as a result of geographical or physiological boundaries between fruit flies.

The splitting of one species into two genetically incompatible species is called speciation. Speciation is shown by the fact that when the two different species interbreed, their offspring are born either sterile or dead. For example, if one were to try to mate dogs and cats together, their offspring would be inviable.

The study hopes to further the advancement of evolutionary genetics and natural selection.

The significance of Presgraves and Tang’s findings are twofold. First, speciation happens by a process of natural selection. Second, the gene that was discovered to lead to speciation doesn’t have a random function. This gene is actually linked to a previously found gene that leads to speciation in fruit flies.

‘The picture we have, then, is that our two fruit fly species split from one another a couple million years ago,” Presgraves said.

The results of the research were surprising to Presgraves, an evolutionary geneticist who has been working on gene development since his time as a graduate student here at UR.

Several years ago, Presgraves discovered a gene called Nup 96, which leads to the speciation in fruit flies. This recently published study is about the new gene he and Tang discovered, Nup 160, that serves the same function.

The anomaly of his finding is that the two genes are related. Both genes encode for portions of the same structure of the cell, a nuclear pore complex.

This complex is an arrangement of proteins that function as a ‘gateway” into and out of the nucleus of the cell. The discovery that both speciation genes are involved in the same function underscores the research.

If the genes aren’t randomly assigned, then the next piece is to look at why these two particular genes are so rapidly evolving that they cause genetic incompatibility between fruit flies. Presgraves was able to show both genes, Nup 160 and Nup 96, rapidly evolve at rates much faster than any of the others in the genome.

The rationale for why Nup 160 and Nup 96 evolve so fast is as follows.
DNA is located inside the nucleus of the cell. The nuclear pore complex of the fruit fly acts as a doorway into the nucleus of the cell.

Adaptations in the nuclear pore complex would be advantageous to the fruit fly in preventing the insertion of viruses into the DNA. The two genes he discovered are both involved in this process of protecting the DNA of the fruit fly and in this way would their rapid evolution would increase chances of survival.

Presgraves says that both genes show signs of natural selection.
‘Their nuclear pore genes evolved different DNA sequences very quickly, and now when we make hybrids between the two, some die because their different nuclear pore genes don’t know how to talk to each other anymore,” Pergraves said. ‘The question for us now is why has natural selection caused the nuclear pore complex genes to evolve so rapidly.”

Presgraves continues his studies in related areas, combining genetic mapping and genomics approaches to determine why X chromosome are a hot spot for speciation genes in two species of Drosophila fruit flies.

Carlin is a member of
the class of 2011.



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