Gradients of decapentaplegic (Dpp) pattern Drosophila wing imaginal discs, establishing gene expression boundaries at specific locations. As discs grow, Dpp gradients expand, keeping relative boundary positions approximately stationary. Such scaling fails in mutants for Pentagone (pent), a gene repressed by Dpp that encodes a diffusible protein that expands Dpp gradients. Although these properties fit a recent mathematical model of automatic gradient scaling, that model requires an expander that spreads with minimal loss throughout a morphogen field. Here, we show that Pent’s actions are confined to within just a few cell diameters of its site of synthesis and can be phenocopied by manipulating non-diffusible Pent targets strictly within the Pent expression domain. Using genetics and mathematical modeling, we develop an alternative model of scaling driven by feedback downregulation of Dpp receptors and co-receptors. Among the model’s predictions is a size beyond which scaling fails—something we observe directly in wing discs.

Decapentaplegic（Dpp）模式果蝇翅假想盘的渐变，在特定位置建立基因表达边界。随着光盘的增长，Dpp梯度会扩大，从而使相对边界位置保持近似固定。这样的缩放在戊五酮（pent）突变体中失败。），由Dpp抑制的基因，其编码可扩散蛋白质的蛋白质，可扩展Dpp梯度。尽管这些属性适合自动梯度缩放的最新数学模型，但该模型需要扩展器，该扩展器在整个形态发生子场中散布的损失最小。在这里，我们表明Pent的作用仅限于其合成位点的几个细胞直径之内，并且可以通过严格地在Pent表达域内操纵不可扩散的Pent靶点进行表型复制。使用遗传学和数学建模，我们开发了由Dpp受体和共受体的反馈下调驱动的缩放的替代模型。在模型的预测中，有一个大小超出了缩放范围，这是我们无法直接在机翼圆盘中观察到的。