Localization of transcripts from the wingless gene in whole Drosophila embryos.

In situ hybridization has been used to detect transcription in whole Drosophila embryos. Improved results have been obtained by incubating the hybridized embryos in liquid emulsion prior to autoradiographic exposure. This technique has been used to map the distribution of transcripts from the segment-polarity gene wingless (wg), which is transcribed in a stripe in each segment of the trunk region. By the extended germband stage additional areas of transcription in the head and caudal regions define a total of 21 domains, comprising the foregut, six regions in the head, three thoracic and ten abdominal segments, and the hindgut. At the end of the extended germband stage, the pattern of wg transcription is no longer uniform in the dorsoventral axis: wg transcripts are absent from the lateral epidermis. This pattern of wg transcription is discussed with particular regard to the segmentation of the terminalia. Also it is suggested that the dorsoventral reorganization could be related to the specification of the imaginal disc primordia.