Microevolutionary support for a developmental hourglass:: gene expression patterns shape sequence variation and divergence in Drosophila
Microevolutionary support for a developmental hourglass:: gene expression patterns shape sequence variation and divergence in Drosophila
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DOI：
10.1111/j.1525-142x.2008.00273.x
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发表时间：
2008-09-01
影响因子：
2.9
通讯作者：
Wade, Michael J.
中科院分区：
文献类型：
--
作者：
Cruickshank, Tami;Wade, Michael J.
进化发育生物学（Evo-Devo）的中心目标是综合比较分子发育遗传学及其对基因型和表型之间动态关系的描述与群体遗传学的微进化过程（突变、随机漂移和选择）。为此，我们分析了五个基因类别的序列变异，这些基因类别依次作用于塑造果蝇早期胚胎发育：母性基因、间隙基因、配对规则基因、片段极性基因和片段同一性基因。我们发现了两种相关的模式：（1）微进化模式，其中母体效应基因的物种内相对序列变异比任何其他基因类别高 2 至 3 倍； (2)宏观进化模式，其中物种间母体效应基因的相对序列差异比任何其他基因类别大2至4倍。这两种模式在定性和定量上都与微进化理论的预测一致。我们的研究结果将种内遗传变异与种间差异联系起来，并揭示了有关“发育沙漏”存在的争议，即胚胎中期阶段比早期或晚期阶段在进化上受到更多限制。由于母体效应基因相对于合子效应基因经历了宽松的选择性约束，因此它们探索了更广泛的突变和表型空间。因此，早期作用的母体效应基因在不同的分类群中差异更大，从而扩大了发育沙漏的基础。相比之下，后来起作用的合子基因在跨类群的多样化方面相对受到更多限制，从而缩小了发育沙漏的腰部。这种模式被具有母体和合子表达的基因所掩盖，这些基因经历了最强的进化限制。
A central goal of evolutionary developmental biology (Evo-Devo) is to synthesize comparative molecular developmental genetics and its description of the dynamic relationship between genotype and phenotype with the microevolutionary processes (mutation, random drift, and selection) of population genetics. To this end, we analyzed sequence variation of five gene classes that act sequentially to shape early embryo development in Drosophila: maternal, gap, pair-rule, segment polarity, and segment identity genes. We found two related patterns: (1) a microevolutionary pattern, wherein relative sequence variation within species is 2- to 3-fold higher for maternal-effect genes than for any other gene class; and, (2) a macroevolutionary pattern, wherein the relative sequence divergence among species for maternal-effect genes is 2- to 4-fold greater than for any other gene class. Both patterns are qualitatively and quantitatively consistent with the predictions of microevolutionary theory. Our findings connect within-species genetic variation to between-species divergence and shed light on the controversy over the existence of a "developmental hourglass," where mid-embryonic stages are more evolutionarily constrained than either earlier or later stages. Because maternal-effect genes experience relaxed selective constraint relative to zygotic-effect genes, they explore a wider mutational and phenotypic space. As a result, early acting maternal-effect genes diverge more widely across taxa and thereby broaden the base of the developmental hourglass. In contrast, later acting zygotic genes are relatively more constrained and limited in their diversification across taxa, narrowing the waist of the developmental hourglass. This pattern is obscured by genes with both maternal and zygotic expression, which experience the strongest evolutionary constraint.