Wang D, Marsh J L, Ayala F J
Developmental Biology Center, University of California, Irvine, CA 92717, USA.
Proc Natl Acad Sci U S A. 1996 Jul 9;93(14):7103-7. doi: 10.1073/pnas.93.14.7103.
The hypothesis that morphological evolution may largely result from changes in gene regulation rather than gene structure has been difficult to test. Morphological differences among insects are often apparent in the cuticle structures produced. The dopa decarboxylase (Ddc) and alpha-methyldopa hypersensitive (amd) genes arose from an ancient gene duplication. In Drosophila, they have evolved nonoverlapping functions, including the production of distinct types of cuticle, and for Ddc, the production of the neurotransmitters, dopamine and serotonin. The amd gene is particularly active in the production of specialized flexible cuticles in the developing embryo. We have compared the pattern of amd expression in three Drosophila species. Several regions of expression conserved in all three species but, surprisingly, a unique domain of expression is found in Drosophila simulans that does occur in the closely related (2-5 million years) Drosophila melanogaster or in the more remote (40-50 million years) Drosophila virilis. The "sudden" appearance of a completely new and robust domain of expression provides a glimpse of evolutionary variation resulting from changes in regulation of structural gene expression.
形态进化可能主要源于基因调控而非基因结构变化这一假说一直难以验证。昆虫之间的形态差异通常在其产生的表皮结构中很明显。多巴脱羧酶（Ddc）和α-甲基多巴超敏（amd）基因起源于古老的基因复制。在果蝇中，它们已经进化出不重叠的功能，包括产生不同类型的表皮，对于Ddc来说，还包括产生神经递质多巴胺和血清素。amd基因在发育中的胚胎中产生特殊的柔性表皮时特别活跃。我们比较了三种果蝇物种中amd基因的表达模式。在所有三个物种中都有几个表达区域是保守的，但令人惊讶的是，在拟果蝇中发现了一个独特的表达域，而在亲缘关系较近（200 - 500万年）的黑腹果蝇或更远缘（4000 - 5000万年）的果蝇中并未出现。一个全新且强大的表达域的“突然”出现，让人得以一窥结构基因表达调控变化所导致的进化变异。
