Fig. 3.

Start1 is expressed in nurse cells of ovaries and the prothoracic cells of the ring gland. Whole-mount RNA in situ hybridization using digoxygenin-labeled Start1 antisense RNA as a probe is shown. (A) Ovariol with egg chambers; nurse cells of stage 10 egg chambers show staining. (B) Praeblastoderm. (C) Blastoderm. (D) Embryo, stage 16; the strongly stained cells are the presumed precursor cells of the PG. (E-J) Brain/ring gland complexes from first larval instar (E) and second larval instar (F). (G-I) third larval instar of different stages: freshly hatched larva (G), feeding larva (H), nonfeeding/crawling larva (I), and white prepupa (J). The difference in expression between the second larva (F) and the young third larva (G) indicates that Start1 transcription is shut off during hatching. Staining conditions were kept constant for all larval stages. No staining was obtained for the sense RNA probes (data not shown). rg, ring gland; b, brain; vg, ventral ganglion. Arrowhead in I indicates unstained corpus allatum cells. (Bar, 40 μm.)