Signposts and snapdragons

Professor Enrico Coen from the John Innes Centre in Norwich has published a new paper in the journal Science, revealing a fascinating genetic mechanism underpinning the evolution of the brightly coloured ‘signposts’ that bees use to home in on the juicy nectar in the centre of snapdragon flowers. Kat Arney caught up with him for a chat about his latest floral findings.

Enrico - In the Pyrenees, there are these two species of snapdragons that have different ways of signposting to bees where the bees can enter the flower. So there's a sort of like a red or magenta flower with a yellow highlight and that’s one species, and then there's another species with yellow flowers and a magenta highlight.

We were trying to understand how these differences arose. I mean, why does one species, one type of signposting species have another type of signpost? And to do this, we started to analyse some of the genes involved that control these different traits. The amazing was that we found out that one of the genes, the genes that controls the yellow highlight arose through a sort of very strange mirror image duplication. So it sort of created a mirror copy of itself.

And through this mirror copy it generated a specific type of molecule called a small RNA, and that molecule is what's involved in restricting the yellow pigmentation. So that was a complete surprise.

People had found these types of mirror image duplications in the laboratory and then we know they're also part of the genome. But to discover that they were responsible for this variation that you see out there in nature, that was fantastic surprise really and that’s what the paper is about, about that discovery.

Kat - When I think back through my history of genetics, I do remember that the first discovery that small bits of RNA could turn genes off was made in petunias. Researchers were trying to make the purple colour in petunias and then they discovered that they accidentally switched the purple gene off. So is that sort of a similar process and is that process widely used in plants?

Enrico - It is a similar process. The petunia story you're talking about is when people were putting genes into petunias artificially. So they were inserting these genes into these plants, and discovered this strange phenomenon. And this is exactly the phenomenon that we’ve discovered except that it’s not through people changing artificially the genomes. It’s happening in nature itself. So that’s the striking thing that actually nature was there way before us in terms of these types of rearrangements and mirror images.

Kat - What's the next step for this now that you’ve discovered this? What are you going to do with the information now you know there is this kind of mirror image thing that switches the colour off?

Enrico - So what we’d really like to know now is how this whole system originated. What we’re seeing today is different signposts. We’d really like understand how did it arise: how did it, how is it that the evolution alone looks at one signpost, one species, another signpost in the other species?

And that’s looking, digging deeper into the genome, looking at how these originated, how these mirror image duplications arose, really looking quite broadly across the different species across their genomes, trying to do experiments to figure out how this remarkable difference arose. It’s a bit of a conundrum. How is it that you end up with two equally good solutions starting from one beginning?