Death comes for the salivary gland

As it morphs from a squirming maggot into a buzzing adult, a fruit fly jettisons its juvenile salivary glands. On page 85, Yin et al. show how the insects get rid of a protective protein, allowing the glands to break down at the right time. The research helps clarify how certain tissues prepare themselves to die.

During metamorphosis, a larva's obsolete internal organs degenerate, and replacements sprout. Surging quantities of the steroid hormone ecdysone spur the salivary glands and other juvenile structures to melt away. Researchers have mapped out some of the molecular details of this deterioration. Ecdysone cranks up several genes, including one called reaper, that trigger salivary gland cells to perish. But getting rid of the glands requires one more change: elimination of a...