Additional file 6: Figure S5.

Last phase of segmentation: from double (primary Delta) to single-segment periodicity (engrailed and secondary Delta). In a 34 LBS embryo (A)Delta still appears at double segment periodicity (large blue arrowheads); intercalated Delta stripes defining the single segment periodicity appear only slightly later, that is, more anteriorly, as the segment pattern matures (small blue arrowheads). engrailed expression (magenta arrowheads) appears yet slightly later than intercalated Delta, overlapping with the segmental stripes of Delta as these fade. engrailed is then expressed persistently in the whole maturing germ band anterior of the segment addition zone. In a 36 LBS embryo (B), the single segment intercalation of Delta appears just after the earliest resolved Delta band; engrailed expression appears closer to this first Delta stripe. By the 43 LBS stage (C), only a single stripe of Delta transcript persists. The transcription of engrailed initiates at a position just one segment anterior to this Delta stripe, but Delta expression has already faded from this anterior region. Scale bar in A1, B1, C1: 100 μm, in A2-C2: 50 μm.

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Brena and Akam BMC Biology 2013 11:112   doi:10.1186/1741-7007-11-112