Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands.
Evodevo. 2011 Apr 19;2:9. doi: 10.1186/2041-9139-2-9.
Hox proteins specify segment identity during embryogenesis and have typical associated expression patterns. Changes in embryonic expression and activity of Hox genes were crucial in the evolution of animal body plans, but their role in the post-embryonic development of lineage-specific traits remains largely unexplored. Here, we focus on the insect Hox genes Ultrabithorax (Ubx) and Antennapedia (Antp), and implicate the latter in the formation and diversification of novel, butterfly-specific wing patterns.
First, we describe a conserved pattern of Ubx expression and a novel pattern of Antp expression in wing discs of Bicyclus anynana butterflies. The discrete, reiterated domains of Antp contrast with the typical expression of Hox genes in single continuous regions in arthropod embryos. Second, we show that this pattern is associated with the establishment of the organizing centres of eyespots. Antp upregulation is the earliest event in organizer development described to date, and in contrast to all genes implicated in eyespot formation, is exclusive to those centres. Third, our comparative analysis of gene expression across nymphalids reveals unexpected differences in organizer determination.
We show that the Antp's recruitment for the formation of novel traits in butterfly wing discs involved the evolution of new expression domains, and is restricted to a particular lineage. This study contributes novel insights into the evolution of Antp expression, as well as into the genetic mechanisms underlying morphological diversification. Our results also underscore how a wider representation of morphological and phylogenetic diversity is essential in evolutionary developmental biology.
Hox 蛋白在胚胎发生过程中指定体节的身份，并具有典型的相关表达模式。Hox 基因在胚胎中的表达和活性的变化在动物体节模式的进化中至关重要，但它们在谱系特异性特征的后生发育中的作用在很大程度上仍未得到探索。在这里，我们关注昆虫 Hox 基因 Ultrabithorax（Ubx）和 Antennapedia（Antp），并暗示后者在形成和多样化新的蝴蝶特有的翅膀模式中发挥作用。
首先，我们描述了 Bicyclus anynana 蝴蝶翅膀盘的 Ubx 表达的保守模式和 Antp 表达的新模式。Antp 的离散、重复的表达域与节肢动物胚胎中典型的 Hox 基因在单个连续区域的表达形成鲜明对比。其次，我们表明这种模式与眼斑组织中心的建立有关。Antp 的上调是迄今为止描述的组织中心发育最早的事件，与所有参与眼斑形成的基因不同，它是这些中心所特有的。第三，我们对 nymphalids 中的基因表达进行的比较分析揭示了组织中心决定的出人意料的差异。
我们表明，Antp 被招募用于在蝴蝶翅膀盘形成新特征涉及新表达域的进化，并且仅限于特定的谱系。这项研究为 Antp 表达的进化以及形态多样化的遗传机制提供了新的见解。我们的研究结果还强调了更广泛的形态和系统发育多样性的代表性在进化发育生物学中的重要性。
