A Developmental Perspective on the Evolution of Insect Wings and Imaginal Discs

0091005JockuschINSECT机翼和想象盘是两项关键创新，它们为它们所描述的分支的壮观成功做出了贡献。然而，这些特征起源的发育基础仍然知之甚少。这里提出的工作是对两种昆虫的翅膀发育进行比较分析，这两种昆虫在形态上保留了更多的祖先的翅膀发育模式，甲虫和美洲血吸虫，以及一种原始的无翅六足动物--天牛的翅膀发育的平行分析。这些比较将被用来解决昆虫进化中的两个重要问题：想象盘的起源是否需要原基分配和盘图案的重大变化，还是源于更有限的发育变化？翅膀是否与祖先节肢动物腿的背侧分支同源，或者它们是从背侧胸腔重新产生的？目前，大多数已知的关于翅膀发育的知识来自单一物种，果蝇黑腹果蝇。在形态水平上，果蝇的翅膀发育是起源的。这项资助建议使用比较分子数据来确定果蝇翅膀在哪些方面是通过保留的祖先机制发展起来的，以及通过可能与想象盘的进化和早期分配有关的新机制在多大程度上发展起来的。这项工作有三个具体目标：(1)通过对基因表达和功能的研究，了解果蝇附属物分配机制在其他昆虫中的保守(部分涉及无翼、蜕皮瘫痪和远端无翼基因之间的相互作用)；(2)比较四个在果蝇翅膀发育中重要的基因--蜗牛、蜗牛、无翅和无翼--在血吸虫和小鼠的翅膀发育中的表达，以及在温热属植物的胸叶中的表达，以确定形成翅膀图案的机制是否广泛保守；(3)结合谱系追踪和激光消融技术确定这些物种翅膀细胞的胚胎来源。

0091005JockuschInsect wings and imaginal discs are two key innovations that have contributed to the spectacular success of the clades that they characterize. However, the developmental basis for the origins of these traits remains poorly understood. The work proposed here is a comparative analysis of wing development in two species of insects that retain morphologically more ancestral modes of wing development, the beetle Tribolium castaneum and the grasshopper Schistocerca americana, and a parallel analysis in one primitively wingless hexapod, the thysanuran Thermobia domestica. These comparisons will be used to address two significant questions in insect evolution: Did the origin of imaginal discs require major changes in both primordium allocation and disc patterning or did it result from more limited developmental changes? Are wings homologous to dorsal branches of ancestral arthropod legs or did they arise de novo from the dorsal thorax? Presently, most of what is known about wing development comes from a single species, the fruit fly Drosophila melanogaster. At a morphological level, wing development in Drosophila is derived. This grant proposes to use comparative molecular data to determine in what respects Drosophila wings develop by retained ancestral mechanisms and to what extent by novel mechanisms that may be related to the evolution and early allocation of imaginal discs. This work has three specific aims: (1) to examine the conservation of the Drosophila appendage allocation mechanism (involving, in part, interactions among the genes wingless, ecapentaplegic, and distal-less) in other insects using studies of gene expression and function; (2) to compare the expression of four genes important in Drosophila wing development- snail, escargot, apterous and wingless- in the developing wings of Schistocerca and Tribolium, and in the thoracic lobes of Thermobia to establish whether the mechanisms that pattern the wing are broadly conserved; (3) to identify the embryonic source of wing cells in these species using a combination of lineage tracing and laser ablation techniques.