Averof M, Akam M
Wellcome/CRC Institute, Cambridge, UK.
Nature. 1995 Aug 3;376(6539):420-3. doi: 10.1038/376420a0.
Crustaceans and insects share a common origin of segmentation, but the specialization of trunk segments appears to have arisen independently in insects and various crustacean subgroups. Such macroevolutionary changes in body architecture may be investigated by comparative studies of conserved genetic markers. The Hox genes are well suited for this purpose, as they determine positional identity along the body axis in a wide range of animals. Here we examine the expression of four Hox genes in the branchiopod crustacean Artemia franciscana, and compare this with Hox expression patterns from insects. In Artemia the three 'trunk' genes Antp, Ubx and abdA are expressed in largely overlapping domains in the uniform thoracic region, whereas in insects they specify distinct segment types within the thorax and abdomen. Our comparisons suggest a multistep process for the diversification of these Hox gene functions, involving early differences in tissue specificity and the later acquisition of a role in defining segmental differences within the trunk. We propose that the branchiopod thorax may be homologous to the entire pregenital (thoracic and abdominal) region of the insect trunk.
甲壳类动物和昆虫有着共同的分节起源，但躯干节段的特化似乎是在昆虫和各种甲壳类动物亚群中独立出现的。身体结构的这种宏观进化变化可以通过对保守遗传标记的比较研究来进行探究。Hox基因非常适合用于此目的，因为它们在广泛的动物中决定了沿身体轴的位置身份。在这里，我们研究了鳃足类甲壳动物卤虫中四个Hox基因的表达，并将其与昆虫的Hox表达模式进行比较。在卤虫中，三个“躯干”基因Antp、Ubx和abdA在均匀的胸部区域中表达于大部分重叠的区域，而在昆虫中，它们在胸部和腹部指定不同的节段类型。我们的比较表明，这些Hox基因功能多样化涉及一个多步骤过程，包括组织特异性的早期差异以及后来在定义躯干内节段差异中发挥作用。我们提出，鳃足类动物的胸部可能与昆虫躯干的整个生殖前（胸部和腹部）区域同源。
