Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
Dev Genes Evol. 2020 May;230(3):213-225. doi: 10.1007/s00427-020-00645-w. Epub 2020 Jan 20.
Size and shape constitute fundamental aspects in the description of morphology. Yet while the developmental-genetic underpinnings of trait size, in particular with regard to scaling relationships, are increasingly well understood, those of shape remain largely elusive. Here we investigate the potential function of the Notch signaling pathway in instructing the shape of beetle horns, a highly diversified and evolutionarily novel morphological structure. We focused on the bull-headed dung beetle Onthophagus taurus due to the wide range of horn sizes and shapes present among males in this species, in order to assess the potential function of Notch signaling in the specification of horn shape alongside the regulation of shape changes with allometry. Using RNA interference-mediated transcript depletion of Notch and its ligands, we document a highly conserved role of Notch signaling in general appendage formation. By integrating our functional genetic approach with a geometric morphometric analysis, we find that Notch signaling moderately but consistently affects horn shape, and does so differently for the horns of minor, intermediate-sized, and major males. Our results suggest that the function of Notch signaling during head horn formation may vary in a complex manner across male morphs, and highlights the power of integrating functional genetic and geometric morphometric approaches in analyzing subtle but nevertheless biologically important phenotypes in the face of significant allometric variation.
大小和形状是形态描述的基本方面。然而，尽管关于特征大小的发育遗传基础，特别是关于比例关系，越来越被理解，但形状的基础仍在很大程度上难以捉摸。在这里，我们研究了 Notch 信号通路在指导甲虫角的形状方面的潜在功能，甲虫角是一种高度多样化和进化新颖的形态结构。我们专注于牛头粪甲虫 Onthophagus taurus，因为在该物种的雄性中存在广泛的角大小和形状范围，以便评估 Notch 信号在规范角形状以及与全异比例调节形状变化方面的潜在功能。使用 RNA 干扰介导的 Notch 和其配体的转录耗竭，我们记录了 Notch 信号在一般附肢形成中的高度保守作用。通过将我们的功能遗传方法与几何形态测量分析相结合，我们发现 Notch 信号对 horns 的形状有适度但一致的影响，并且对小、中、大 horns 的影响方式不同。我们的研究结果表明，Notch 信号在头部角形成过程中的功能可能在不同的雄性形态中以复杂的方式变化，并突出了在面对显著的全异比例变化时，整合功能遗传和几何形态测量方法分析微妙但仍然具有生物学重要性的表型的能力。
