Tubes go apical

Delivery of apical membrane drives tube growth, according to Monn Monn Myat and Deborah Andrew (Johns Hopkins University, Baltimore, MD). Although the initial step of tube formation involves constriction of the apical membrane to allow cell involution, the subsequent expansion of apical membrane supplies the raw material for tube elongation.

The tubes in question are the salivary glands of flies, but Andrew thinks her results extend far beyond fly spit. “I think it's going to be a unifying phenomenon,” she says. “You can do a lot by controlling when and where membrane is delivered.”

Earlier workers had put forward the apical membrane hypothesis. But the Johns Hopkins team has now supplied the field with some handy molecular markers for the process. They found that the patterning gene hairy suppresses both excessive branching and expansion...