Data from: Intra-organ growth coordination in Drosophila is mediated by systemic ecdysone signaling

Regulation of final organ size is a complex developmental process that
involves the integration of systemic and organ-specific processes.
Previously, we have shown that in developing Drosophila, perturbing the
growth of one imaginal disc – the parts of a holometabolous larva that
become the external adult organs – retards growth of other discs and
delays development, resulting in tight inter-organ growth coordination and
the generation of a correctly proportioned adult. Whether different parts
of the same imaginal disc similarly coordinate their growth to generate a
functioning adult organ is, however, unclear. In this study, we use the
wing imaginal disc in Drosophila to study and identify mechanisms of
intra-organ growth coordination. We generate larvae in which the two
compartments of the wing imaginal disc have ostensibly different growth
rates (wild-type or growth-perturbed). We find that there is tightly
coordinated growth between the wild-type and growth-perturbed
compartments, where growth of the wild-type compartment is retarded to
match that of the growth-perturbed compartment. Crucially, this
coordination is disrupted by application of exogenous 20-hydroxyecdysone
(20E), which accelerates growth of the wild-type compartment. We further
elucidate the role of 20E signaling in growth coordination by showing that
in wild-type discs, compartment-autonomous up-regulation of 20E signaling
accelerates compartment growth and disrupts coordination. Interestingly,
growth acceleration through exogenous application of 20E is inhibited with
suppression of the Insulin/Insulin-like Growth Factor Signaling (IIS)
pathway. This suggests that an active IIS pathway is necessary for
ecdysone to accelerate compartment growth. Collectively, our data indicate
that discs utilize systemic mechanisms, specifically ecdysone signaling,
to coordinate intra-organ growth.