Kelsh R, Weinzierl R O, White R A, Akam M
Wellcome/CRC Institute, Cambridge, United Kingdom.
Dev Genet. 1994;15(1):19-31. doi: 10.1002/dvg.1020150104.
To investigate what role homeotic genes may play in morphological evolution, we are comparing homeotic gene expression in two very different insects, Drosophila (Diptera) and Schistocerca (Orthoptera). In this paper we describe a monoclonal antibody, FP6.87, that recognizes the products of both the Ultrabithorax (Ubx) and abdominal-A (abd-A) genes in Drosophila, via an epitope common to the carboxy terminal region of these two proteins. This antibody recognizes nuclear antigens present in the posterior thorax and abdomen of Schistocerca. We infer that it recognizes the Schistocerca homolog of UBX protein, and probably also of ABD-A. As the distribution of Schistocerca ABD-A protein is already known, we can use this reagent to map the expression of Schistocerca UBX in the thorax and anterior abdomen, where ABD-A is not expressed. Both the general domain, and many of the details, of UBX expression are remarkably conserved compared with Drosophila. Thus UBX expression extends back from T2 in the ectoderm (including the CNS), but only from A1 in the mesoderm. As noted for other bithorax complex genes in Schistocerca, expression begins in the abdomen, at or shortly before the time of segmentation. It only later spreads anteriorly to the thorax. For much of embryogenesis, the expression of UBX in the thoracic epidermis is largely restricted to the T3 limb. In this limb, UBX is strikingly regulated, in a complex pattern that reflects limb segmentation. Reviewing these and earlier observations, we conclude that evolutionary changes affect both the precise regulation of homeotic genes within segments, and probably also the spectrum of downstream genes that respond to homeotic gene expression in a given tissue. Overall domains of homeotic gene expression appear to be well conserved between different insect groups, though a change in the extent and timing of homeotic gene expression may underlie the modification of the posterior abdomen in different insect groups.
为了研究同源异型基因在形态进化中可能发挥的作用，我们正在比较两种截然不同的昆虫——果蝇（双翅目）和沙漠蝗（直翅目）——中的同源异型基因表达情况。在本文中，我们描述了一种单克隆抗体FP6.87，它通过果蝇中Ultrabithorax（Ubx）基因和腹部A（abd - A）基因产物羧基末端区域的一个共同表位，识别这两个基因的产物。该抗体识别沙漠蝗后胸和腹部中存在的核抗原。我们推断它识别的是UBX蛋白的沙漠蝗同源物，可能还有ABD - A的同源物。由于沙漠蝗ABD - A蛋白的分布已经为人所知，我们可以使用这种试剂来绘制沙漠蝗UBX在胸和前腹部的表达图谱，因为ABD - A在这些部位不表达。与果蝇相比，UBX表达的总体区域以及许多细节都显著保守。因此，UBX在外胚层（包括中枢神经系统）中的表达从T2向后延伸，但在中胚层中仅从A1开始。正如在沙漠蝗中其他双胸复合体基因所观察到的那样，表达始于腹部，在分节时或分节前不久开始。它只是后来向前扩散到胸部。在胚胎发育的大部分时间里，UBX在胸表皮中的表达主要局限于T3肢体。在这个肢体中，UBX受到显著调控，其模式复杂，反映了肢体分节情况。回顾这些以及早期的观察结果，我们得出结论，进化变化既影响同源异型基因在节段内的精确调控，也可能影响给定组织中对同源异型基因表达作出反应的下游基因谱。尽管同源异型基因表达的范围和时间变化可能是不同昆虫类群后腹部形态改变的基础，但同源异型基因表达的总体区域在不同昆虫类群之间似乎保守性良好。
