Molecular biologist Sebastian Alvarado of Stanford University in Palo Alto, California, and colleagues suspected that the mechanism involves DNA methylation: the addition of a chemical to DNA. Cells typically use DNA methylation to shut down the activity of specific genes, and past studies have suggested it alters growth in social insects.
The researchers wanted to nail down which genes dictate the ants’ size. They measured the activity of several growth-controlling genes and found that the one whose activity increased the most in minor workers was the epidermal growth factor receptor (EGFR), suggesting it was responsible for their daintiness. Sure enough, the researchers found that blocking EGFR with a drug produces larger workers.
This discovery “takes the field leaps and bounds forward,” says entomologist Andrew Suarez of the University of Illinois, Urbana-Champaign, who wasn’t connected to the study. “It’s providing a better understanding of how genes interact with the environment to generate diversity.”