Indirect flight muscles (IFMs) are the largest muscles in Drosophila and are made up of hundreds of myonuclei. The generation of these giant muscles requires a large pool of wing disc associated adult muscle precursors (AMPs), however the factors that control proliferation to form this myoblast pool are incompletely known. Here, we examine the role of fibroblast growth factor (FGF) signaling in the proliferation of wing disc associated myoblasts. We find that the components of FGF signaling are expressed in myoblasts and surrounding epithelial cells of the wing disc. Next, we show that attenuation of FGF signaling results in a diminished myoblast pool. This reduction in the pool size is due to decreased myoblast proliferation. By contrast, activating the FGF signaling pathway increases the myoblast pool size and restores the proliferative capacity of FGF knockdown flies. Finally, our results demonstrate that the FGF receptor Heartless acts through up-regulating β-catenin/Armadillo signaling to promote myoblast proliferation. Our studies identify a novel role for FGF signaling during IFM formation and uncover the mechanism through which FGF coordinates with Wingless signaling to promote myoblast proliferation.

间接飞行肌 (IFM) 是果蝇中最大的肌肉并且由数百个肌核组成。这些巨大肌肉的产生需要大量与翼盘相关的成体肌肉前体 (AMP)，但控制增殖形成此成肌细胞池的因素尚不完全清楚。在这里，我们检查了成纤维细胞生长因子 (FGF) 信号在翼盘相关成肌细胞增殖中的作用。我们发现 FGF 信号的成分在成肌细胞和翼盘周围的上皮细胞中表达。接下来，我们表明 FGF 信号减弱导致成肌细胞池减少。池大小的这种减少是由于成肌细胞增殖减少。相比之下，激活 FGF 信号通路会增加成肌细胞池的大小并恢复 FGF 敲低果蝇的增殖能力。最后，我们的结果表明，FGF 受体 Heartless 通过上调 β-catenin/Armadillo 信号来促进成肌细胞增殖。我们的研究确定了 FGF 信号在 IFM 形成过程中的新作用，并揭示了 FGF 与 Wingless 信号协同促进成肌细胞增殖的机制。