Hatzopoulos A K, Regier J C
Proc Natl Acad Sci U S A. 1987 Jan;84(2):479-83. doi: 10.1073/pnas.84.2.479.
Discrete changes in silkmoth choriogenesis have occurred during evolution, as exemplified in the present report in Antheraea polyphemus and Hyalophora cecropia. At the level of morphology, the chorion of A. polyphemus has surface structures, called aeropyle crowns, that are absent from H. cecropia. Aeropyle crowns form during the very late period of choriogenesis and consist of two substructures--lamellae and filler. Filler is present in H. cecropia in greatly reduced amounts. At the level of protein synthesis, overall similarities in the two species are maintained until the very late period of choriogenesis, when synthesis of aeropyle crown components is maximal. In H. cecropia, very late period-specific proteins are reduced in number and abundance. Several of these minor proteins are candidates for E1 and E2, the components of filler. E1 and E2 RNAs are about 35 times more abundant in A. polyphemus, despite very similar gene copy numbers and times of expression in the two species. These results support the hypothesis that evolutionary changes in chorion morphology have resulted from regulatory changes in the expression of chorion genes, either at the level of transcription or mRNA decay. The hypothesis that evolutionary changes in chorion morphology are based on terminal addition onto a preexisting developmental program is discussed.
蚕蛾卵壳发生过程中的离散变化在进化过程中已经出现，如本报告中多音天蚕（Antheraea polyphemus）和樗蚕（Hyalophora cecropia）的例子所示。在形态学水平上，多音天蚕的卵壳具有称为气室冠的表面结构，而樗蚕的卵壳则没有。气室冠在卵壳发生的非常后期形成，由两个亚结构——薄片和填充物组成。填充物在樗蚕中的含量大大减少。在蛋白质合成水平上，这两个物种在卵壳发生的非常后期之前保持总体相似性，此时气室冠成分的合成达到最大值。在樗蚕中，非常后期特异性蛋白质的数量和丰度都有所减少。这些次要蛋白质中的几种是填充物成分E1和E2的候选者。尽管这两个物种的基因拷贝数和表达时间非常相似，但E1和E2 RNA在多音天蚕中的丰度大约高35倍。这些结果支持了这样一种假设，即卵壳形态的进化变化是由卵壳基因表达的调控变化引起的，无论是在转录水平还是mRNA降解水平。本文还讨论了卵壳形态的进化变化基于在预先存在的发育程序上进行末端添加的假设。
