Apoptosis controls the speed of looping morphogenesis in XXXX male terminalia.

@entity717 @entity4998 @entity238 @entity34206
In metazoan development, the precise mechanisms that regulate the completion of morphogenesis according to a developmental timetable remain elusive. The @entity238 male terminalia is an asymmetric looping organ; the internal @entity4998 (spermiduct) loops dextrally around the hindgut. Mutants for apoptotic signaling have an orientation defect of their male terminalia, indicating that apoptosis contributes to the looping morphogenesis. However, the physiological roles of apoptosis in the looping morphogenesis of male terminalia have been unclear. Here, we show the role of apoptosis in the organogenesis of male terminalia using time-lapse imaging. In normal flies, @entity717 accelerated as development proceeded, and completed a full 360   rotation. This acceleration was impaired when the activity of caspases or @entity34206 or PVF/PVR signaling was reduced. Acceleration was induced by two distinct subcompartments of the A8 segment that formed a ring shape and surrounded the male @entity4998 : the inner ring rotated with the @entity4998 and the outer ring rotated later, functioning as a 'moving walkway' to accelerate the inner @entity717 . A quantitative analysis combining the use of a FRET-based indicator for caspase activation with single-cell tracking showed that the timing and degree of apoptosis correlated with the movement of the outer ring, and upregulation of the apoptotic signal increased the speed of @entity717 . Therefore, apoptosis coordinates the outer ring movement that drives the acceleration of @entity717 , thereby enabling the complete morphogenesis of male @entity4998 within a limited developmental time frame.
