Revision 1

Accepted · first revision · record

Title: Mechanism of morphogen gradient scaling in growing tissue
Plain: The signaling molecule Dpp forms a concentration gradient across the fly wing, and its decay length grows in proportion to the wing as it grows. Which chemistry keeps this proportion is disputed.
Precise: In the Drosophila wing disc, the Dpp gradient decay length $\lambda$ scales with disc length $L$ during growth, $\lambda/L \sim \mathrm{constant}$ (Wartlick and co-workers, 2011). Identify which parameter in $\lambda = \sqrt{D/k}$ ($D$ = effective diffusion constant, $k$ = degradation rate) is regulated and by which feedback (expander-repressor via Pentagone, intracellular recycling of Dpp, dilution by growth, receptor regulation), with a model that predicts $\lambda(L)$ in mutants.
Settled by: Measurement of $D$ and $k$ versus disc size in wild type and feedback mutants, showing which one changes to keep $\lambda / L$ fixed.
Kind: well-posed
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: 2011