WASHINGTON — Despite what you might’ve seen in 1950s monster movies, it’s difficult to raise mutant ants. For years, biologists have altered the genetics of organisms as varied as mice and rice. Mutant fruit flies are a laboratory staple. But ants’ complex life cycle hampered efforts to grow genetically engineered ants — until now.
On Thursday, two independent research teams described their work deleting ant genes. Two papers chronicling the first mutant ants appeared in the journal Cell, along with a third study that altered ant behavior using an insect brain hormone.
Claude Desplan, a New York University biologist and an author of one of the studies, said that, as far as he could tell, these ants are ‘‘the first mutant in any social insect.’’
Ants have complex social roles, even though members of a colony are genetically very similar. Females may be egg-laying queens or sterile workers, colony cleaners or fierce soldiers. Males, who are little more than sperm-delivery systems with wings, appear only seasonally. To ensure the mutant genes carry on, ‘‘you need to go through the queen,’’ Desplan said. ‘‘It is not so easy to make queens.’’
‘‘There’s a lot of interesting biologic questions that you can study with ants that you can’t study with fruit flies or even mice,’’ said Rockefeller University biologist Daniel Kronauer, an author of the other mutant-ant study.
What’s more, the insects are prime targets for studies of epigenetics, the external factors that toggle genes on and off. ‘‘Ants are amazing because with the same genome you can be a queen, or a worker, or another class of worker, or a soldier,’’ Desplan said.
Desplan’s research group studied a species of jumping ant found in India, Harpegnathos saltator, because all of these ants are potentially fertile. Before laying eggs, though, the workers have to become pseudo-queens. Kronauer and colleagues, led by Rockefeller University graduate student Waring Trible, studied clonal raider ants, Ooceraea biroi. Unlike most ants, the raider ants reproduce asexually.
The desired result of genetic alteration was the same: creating mother ants that gave birth to future generations of mutants. Using the CRISPR-Cas9 technique, with bacterial molecules acting like scissors to snip out genes, the scientists knocked out a crucial component of the ant’s odor receptors.
Pheromones, the odors by which ants communicate, are their social medium.
The behavior of the mutants changed dramatically.
Like the jumping ants, the Ooceraea biroi mutants became antisocial. ‘‘Suddenly these ants aren’t really social any more. They wander off, they don’t join the colony,’’ Kronauer said.
