Tiny changes in gene expression can lead to big differences in eye size of fruit flies

An international team of scientists has discovered that tiny changes in the timing of the expression of a single gene can lead to big differences in eye size. Gene expression is the process by which the information encoded in a gene is turned into a functional output, for example, the production of a protein.

Researchers including Professor Alistair McGregor, in Durham University’s Department of Biosciences, looked at two closely related species of fruit fly—Drosophila mauritiana and Drosophila simulans.

They found that a slight change in the timing of expression of a gene called orthodenticle (otd) can cause a significant difference in the size of the ommatidia, the individual hexagonal units that make up a compound eye.

In Drosophila mauritiana, otd is expressed earlier in eye development than in Drosophila simulans. This is associated with an increase in the ommatidia size of Drosophila mauritiana, meaning the eyes of this species are larger.

“Insects exhibit extensive variation in the shape and size of their eyes, which contributes to adaptive differences in their vision. Our study comparing Drosophila species that differ in eye size reveals one of the genetic mechanisms that can make the facets of their eyes bigger and potentially allow greater contrast sensitivity,” says McGregor.

The work is published in the journal BMC Biology.

The researchers say their findings could have implications for our understanding of how the size of other organs evolve. They are now planning to investigate whether similar changes in gene expression can lead to differences in the size of other organs.