A light has been shone on a gene that controls the shape of tomatoes.

In this week’s Science, a team of US researchers report that duplicating the SUN gene – named for the Sun 1642 tomato variety in which it was found – causes these fruit to have an elongated shape.

“We are trying to understand what kind of genes caused the enormous increase in fruit size and variation in fruit shape as tomatoes were domesticated,” says Esther van der Knaap, crop science expert at Ohio State University (press release). “Once we know all the genes that were selected during that process, we will be able to piece together how domestication shaped the tomato fruit — and gain a better understanding of what controls the shape of other very diverse crops, such as peppers, cucumbers and gourds.”

Most of the coverage of this focuses on the fact that scientists have found a gene for wonky tomatoes. Actually van der Knaap’s team have produced something more interesting.

Their research suggests that natural duplication of the SUN gene was caused by something called a retrotransposon. The Scientist’s piece gets into the details of this:

Parasitic genetic elements known as retrotransposons replicate themselves throughout the genome, often dragging along other fragments of DNA in the process. But these DNA elements usually disrupt gene function. So it was surprising to find that the retrotransposon-mediated duplication led to an overexpression of the sun gene, which the authors suggest might ramp up levels of auxin, a key plant hormone.

So, suggest the researchers, this study shows “retrotransposons may be a major driving force in genome evolution and gene duplication”. Which isn’t as simple as “wonky gene found”, but is more important to my mind.

Image: Science