In insects, imaginal discs control the transition from larva to adult. The discs must grow and differentiate in order to form an adult of reasonable size with all of its normal legs and wings. Truman et al. (see the Perspective by Léopold and Layalle) now analyze the processes controlling disc growth and differentiation in the Manduca larva. Cellular proliferation in the discs depends on how well fed the larva was, whereas differentiation into adult structures is managed by juvenile hormone, the presence of which represses differentiation.
J. W. Truman, K. Hiruma, J. P. Allee, S. G. B. MacWhinnie, D. T. Champlin, L. M. Riddiford, Juvenile hormone is required to couple imaginal disc formation with nutrition in insects. Science 312, 1385-1388 (2006). [Abstract] [Full Text]