A protein-coding gene called GB45239 is responsible for thelytokous parthenogenesis — the ability to produce daughters asexually — in the Cape honeybee (Apis mellifera capensis), a subspecies of honeybee found in the two southern provinces of South Africa, according to a new paper published in the journal Current Biology.
A ‘super’ Cape honeybee worker (black in center) is nearly as big as a queen (with white disc). Image credit: Benjamin Oldroyd, University of Sydney.
The female worker caste of the honeybees typically does not reproduce in the presence of the pheromones produced by the queen and the brood.
Whenever the queen and her pheromonal control are absent, workers are able to activate their ovaries and parthenogenetically produce haploid male offspring — arrhenotoky.
A rare exception to worker arrhenotoky is the thelytokous parthenogenetic production of female offspring by laying workers, which is a characteristic of the Cape honeybee.
“It is extremely exciting,” said co-lead author Professor Benjamin Oldroyd, a researcher in the School of Life and Environmental Sciences at the University of Sydney.
“Scientists have been looking for this gene for the last 30 years. Now that we know it’s on chromosome 11, we have solved a mystery.”
The GB45239 gene has allowed Cape honeybee workers to lay eggs that only produce females instead of the normal males that other honeybees do.
“Males are mostly useless. But Cape workers can become genetically reincarnated as a female queen and that prospect changes everything,” Professor Oldroyd said.
But GB45239 also causes problems. Instead of being a cooperative society, Cape honeybee colonies are riven with conflict because any worker can be genetically reincarnated as the next queen.
When a colony loses its queen the workers fight and compete to be the mother of the next queen.
“Further study of Cape bees could give us insight into two major evolutionary transitions: the origin of sex and the origin of animal societies,” Professor Oldroyd said.
Perhaps the most exciting prospect arising from this study is the possibility to understand how the GB45239 gene actually works functionally.
“If we could control a switch that allows animals to reproduce asexually, that would have important applications in agriculture, biotechnology and many other fields,” Professor Oldroyd said.
“For instance, many pest ant species like fire ants are thelytokous, though unfortunately it seems to be a different gene to the one found in Apis mellifera capensis.”
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Boris Yagound et al. A Single Gene Causes Thelytokous Parthenogenesis, the Defining Feature of the Cape Honeybee Apis mellifera capensis. Current Biology, published online May 7, 2020; doi: 10.1016/j.cub.2020.04.033
