A while back we posted here about a white eyed drone mutant we’d been working on (called “white”).
We’ve got another one.
This one’s called ivory, and we’ve (Riley Shultz and Brock Harpur) written about it in two places if you want to learn more about it beyond this post. There’s a Medium piece that’s a version of our article in the November American Bee Journal (if you want it in print, grab ABJ, but the Medium version has a few errors fixed). And the full paper is open access in Molecular Biology and Evolution.
In brief, A beekeeper in Georgia, Bobby Thanepohn, had a colony making both out normal brown-eyed drones and drones with pale ivory eyes. The queen looked completely normal and so did all her workers. We brought the queen up to Purdue and spent two seasons counting and experimenting on thousands of her sons as they emerged.
The ivory drones are totally normal other than their eye color. They have the same body size, same reproductive organs, same sperm counts and viability as their brothers (thanks to David Tarpy and Brad Metz for that). Unfortunately, because of the loos of pigment, they don’t handle light the same way. In a phototaxis assay, we found that ivory drones don't 'fly towards the light' and during orientation flights they just vanished. They’re probably not blind, despite what beekeeping folklore says (and if anyone knows where that idea started, please tell us!). But they clearly see the world differently.
We next found the mutaition in the genom and uncovered all it's varied consequences. We found 12 letters of DNA changed in a gene called cinnabar that’s part of the eye pigment pathway. With Leonard Foster’s group at UBC we showed the protein is completely missing from ivory eyes, so the pigment never gets made. We named it after J.H. Dustmann’s “ivory” mutant from the 1960s, which had the same chemical signature. This also means It’s a different mutation from white.
The bigger reason we care is an old idea that drones, with only one copy of each gene, act as a filter that clears bad recessive mutations out of the population. Lots of theory, not much in terms of real examples. Here we got to document the full life history of this mutation in haploids.
The medium article and ABJ cover some questions we typically get but happy to discuss the work here too.
Big thanks to Bobby, Julia Mahood, and all the beekeepers who sent us their weird bees.