Figure 1: Overview of key concepts in egg chamber elongation.

(a) Illustration of an ovariole, a developmental array of egg chambers. Egg chambers are spherical when they bud from the germarium and then lengthen along their anterior–posterior axes as they develop. (b) Blowup of the boxed region in a highlighting the apical–basal axis of the follicle cell epithelium. (c) The ‘molecular corset’ consists of parallel arrays of actin bundles at the basal epithelial surface (stage nine) and fibril-like structures in the adjacent basement membrane (stage seven). Laser-scanning confocal images. Scale bar, 10 μm. (d) Transverse section through a stage seven egg chamber, as shown by the dashed line in a. The egg chamber rotates within the surrounding basement membrane (illustration adapted from ref. 32).