Fig. 1

mRNA expression of the pair-rule genes eve (a-a’), odd (b, b′), sob (c-c′), and run (d-d’) in embryos at early and late abdominal segmentation. In the early segmenting germband (44–46 h after egg laying (hAEL)), eve (a), odd (b) and sob (c) all display a similar expression pattern in the anterior growth zone (GZ) composed of 4–6 stripes, corresponding to nascent segments. The main difference between the expression pattern of these genes is most notable in the posterior GZ where eve is steadily expressed, whereas odd and sob show weaker and graduated expression. Run (d-d’) expression is very different form the other three genes. It is expressed in two broad stripes corresponding to the anterior and posterior GZ, and in patches in the anterior thoracic and gnathal segments. In late germband stages (50–52 hAEL) (a’- d’) we see striped pattern of eve, odd and sob maintained, but with a smaller number of stripes. Expression of run is decreased to a single broad band in the anterior GZ. In addition, odd, sob and run are expressed in the limb buds. Embryos were chosen from within the aforementioned age range to be as similar as possible in developmental stage, based on size and shape of the germband and growth zone. In all images anterior is to the top. Abbreviations: gz, growth zone; hl, head lobe; md, mandibular segment; mx, maxillary segment; lb., labial segment