How the Gene Works: Stop Eating and Grow Up!
"In insects, the larval period is exclusively devoted to growth," says Thummel. "Insects are pests because, in their larval form, they consume many times their body weight in food, which can include our crops. ?When babies are born, they are 7 or 8 pounds. By the time they are entering puberty, they are about 80 pounds. That's about a 10-fold increase in weight. Innocent childhood is a period essentially dedicated to growth, much like insects."
But while human teenagers often are voracious, fruit fly larvae wander away from food and stop eating when it's time to mature into pupae.
The scientists concluded that the DHR4 gene controls the timing of metamorphosis and its initial stages by coordinating how hormones respond when a fruit fly larva has gained enough weight ?and stored enough food ?to begin the transformation to adulthood.
When the gene was deactivated, larvae did not know whether or not they had gained enough weight, so they entered metamorphosis one day early and began adulthood as prepupae that were 40 percent lighter than normal and 60 percent to 90 percent of normal length.
Thummel concludes: "Our life cycle consists of embryonic development, growth, maturation, aging and then death. We have a good handle on how embryonic development and aging work at a molecular level. But the transition from growth to maturation is poorly understood. If we can study this further in insects using them as a model for humans, because they have so many components that also are present in humans, we can gain some insights into how these processes ?the timing of maturation and maturation itself ?work in all higher organisms, including people."