Lawrence P A, Johnston P, Macdonald P, Struhl G
Nature. 1987;328(6129):440-2. doi: 10.1038/328440a0.
One of the earliest molecular signs of segmentation in Drosophila embryos is the striped expression of some pair-rule genes during the blastoderm stage. Two of these genes, fushi-tarazu (ftz) and even-skipped (eve) are expressed during this stage in complementary patterns of seven stripes which develop and disappear in concert. Here, we map the cells expressing each of these two pair-rule genes with respect to the 14 stripes of cells expressing the engrailed gene. We find that both ftz and eve generate stripes which have sharp boundaries at the anterior margin, but fade away posteriorly. The anterior boundaries correspond cell by cell with the anterior boundaries of expression of the engrailed gene. We therefore suggest that a key function of early ftz and eve gene activity is the formation of a sharp stable boundary at the anterior margin of each stripe. These boundary lines, rather than the narrowing zonal stripes, would delimit the anterior boundaries of engrailed and other homoeotic genes and thereby subdivide the embryo into parasegments.
果蝇胚胎中最早的分节分子迹象之一是在囊胚期一些成对规则基因的条纹状表达。其中两个基因，腹节基因（ftz）和偶数缺口基因（eve），在这个阶段以七条条纹的互补模式表达，这些条纹协同发育并消失。在这里，我们根据表达engrailed基因的14条细胞条纹，绘制出表达这两个成对规则基因的细胞图谱。我们发现ftz和eve基因都产生条纹，这些条纹在前缘有清晰的边界，但在后缘逐渐消失。前缘边界与engrailed基因表达的前缘边界逐个对应。因此我们认为，早期ftz和eve基因活性的一个关键功能是在每条条纹的前缘形成清晰稳定 的边界线。这些边界线，而不是变窄的带状条纹，将界定engrailed基因和其他同源异型基因 的前缘边界，从而将胚胎细分为副节段
