Int. J. Dev. Biol. 52: 913 - 923 (2008)

https://doi.org/10.1387/ijdb.082576jy

Vol 52, Issue 7

Maternal RNAs encoding transcription factors for germline-specific gene expression in Drosophila embryos

Original Article | Published: 1 September 2008

Jun Yatsu^1,2, Makoto Hayashi^1,2, Masanori Mukai³, Kayo Arita⁴, Shuji Shigenobu^1,5 and Satoru Kobayashi^1,2,*

¹Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, Higashiyama, Myodaiji, Okazaki, ²Department of Basic Biology, School of Life Science, Graduate University for Advanced Studies, Myodaiji, Okazaki, ³Department of Biology, Faculty of Science and Engineering, Konan University, Kobe, ⁴Clinical Research Center for Blood Diseases, National Hospital Organization Nagoya Medical Center, Nagoya and ⁵Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan

Abstract

In early Drosophila embryos, germ plasm is localized to the posterior pole region and is partitioned into the germline progenitors, known as pole cells. Germ plasm contains the maternal factors required for germline development. It has been proposed that germline-specific gene expression is initiated by the function of maternal factors that are enriched in the germ plasm. However, such factors have remained elusive. Here, we describe a genome-wide survey of maternal transcripts that encode for transcription factors and are enriched in the germ plasm. We isolated pole cells from blastodermal embryos by fluorescence-activated cell sorting (FACS) and then used these isolated cells in a microarray analysis. Among the 835 genes in the Gene Ontology (GO) category “transcription regulator activity” listed in FlyBase, 68 were found to be predominantly expressed in pole cells as compared to whole embryos. As the early pole cells are known to be transcriptionally quiescent, the listed transcripts are predicted to be maternal in origin. Our in situ hybridization analysis revealed that 27 of the 68 transcripts were enriched in the germ plasm. Among the 27 transcripts, six were found to be required for germline-specific gene expression of vasa and/or nanos by knockdown experiments using RNA interference (RNAi). The identified transcripts encode a transcriptional activator (ovo), components of the transcriptional initiation complexes (Trf2, bip2 and Tif-IA), and the Ccr4-Not complex (CG31716 and l(2)NC136). Our study demonstrates that germ plasm contains maternal transcripts encoding transcriptional regulators for germline-specific gene expression in pole cells.

Keywords

germ line, germ plasm, pole cell, transcription factor, Drosophila