Current Biology
Volume 8, Issue 4, 12 February 1998, Pages 243-246
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Regulation of zygotic gene expression in Drosophila primordial germ cells

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Abstract

Activation of the zygotic genome is a prerequisite for the transition from maternal to zygotic control of development. The onset of zygotic transcription has been well studied in somatic cells, but evidence suggests that it is controlled differently in the germline. In Drosophila, zygotic transcription in the soma has been detected as early as one hour after egg laying (AEL) [1]. In the germline, general RNA synthesis is not detected until 3.5 hours AEL (stage 8) [2] and poly(A)-containing transcripts are not observed in early germ cell nuclei [3]. However, rRNA gene expression has been demonstrated at this time [4]. Therefore, either there is a general, low level activation of the genome in early germ cells, or specific classes of genes, such as those transcribed by RNA polymerase (RNAP) II, are repressed. We addressed this issue by localizing the potent transcriptional activator Gal4–VP16 to the germline, and we find that Gal4–VP16-dependent gene expression is repressed in early germ cells. In addition, localization of germ plasm to the anterior reveals that it is sufficient to repress Bicoid-dependent gene expression. Thus, even in the presence of known transcriptional activators, RNAP II dependent gene expression is actively repressed in early germ cells. Furthermore, once the germ cell genome is activated, we find that vasa is expressed specifically in germ cells. This expression does not require proper patterning of the soma, indicating that it is likely to be controlled by the germ plasm.

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MV Doren, AL Williamson and R Lehmann, Skirball Institute and Howard Hughes Medical Institute, NYU Medical Center, 540 1st Avenue, New York, New York 10016, USA.

Present address for AL Williamson, Incyte Pharmaceuticals, Inc., 3174 Porter Drive, Palo Alto, California 94304, USA.

E-mail address for R Lehmann (corresponding author): [email protected].