Raff R A, Anstrom J A, Huffman C J, Leaf D S, Loo J H, Showman R M, Wells D E
Nature. 1984;310(5975):312-4. doi: 10.1038/310312a0.
A rich diversity of ancient sea urchin lineages survives to the present. These include several advanced orders as well as the cidaroids, which represent the group ancestral to all other sea urchins. Here we show that all advanced groups of sea urchins examined possess in their eggs a class of maternal messenger RNA (mRNA) encoded by the evolutionarily highly conserved alpha-subtype histone genes. The maternal histone mRNAs are unique in their time of accumulation in oogenesis, their localization in the egg nucleus and their delayed timing of translation after fertilization. Cidaroid sea urchins as well as other echinoderm classes, such as starfish and sea cucumbers, possess the genes but do not have maternal alpha-subtype histone mRNAs in their eggs. Thus, although all the echinoderms examined transcribe alpha-subtype histone genes during embryogenesis, the expression of these genes as maternal mRNAs is confined to advanced sea urchins. The fossil record allows us to pinpoint the evolution of this mode of expression of alpha-histone genes to the time of the splitting of advanced sea urchin lineages from the ancestral cidaroids in a radiation which occurred in a relatively brief interval of time approximately 190-200 Myr ago. The origin of a unique gene regulatory mechanism can thus be correlated with a set of macroevolutionary events.
多种古老的海胆谱系一直存活至今。这些谱系包括几个高等目以及头帕目，头帕目代表了所有其他海胆的祖先类群。在此我们表明，所有接受检测的高等海胆类群，其卵中都有一种由进化上高度保守的α亚型组蛋白基因编码的母源信使核糖核酸（mRNA）。母源组蛋白mRNA在卵子发生过程中的积累时间、在卵细胞核中的定位以及受精后翻译时间的延迟方面都很独特。头帕目海胆以及其他棘皮动物纲，如海星和海参，拥有这些基因，但它们的卵中没有母源α亚型组蛋白mRNA。因此，尽管所有接受检测的棘皮动物在胚胎发育过程中都转录α亚型组蛋白基因，但这些基因作为母源mRNA的表达仅限于高等海胆。化石记录使我们能够确定这种α组蛋白基因表达模式的进化时间，即大约在1.9亿至2亿年前的一个相对短暂的时间间隔内，高等海胆谱系从祖先头帕目中分化出来的时期。因此，一种独特的基因调控机制的起源可以与一系列宏观进化事件联系起来。
