The role of binding site cluster strength in Bicoid-dependent patterning in Drosophila

Amanda Ochoa-Espinosa, Gozde Yucel, Leah Kaplan, Adam Pare, Noel Pura, Adam Oberstein, Dmitri Papatsenko, Stephen Small

Research output: Contribution to journalArticle

Abstract

The maternal morphogen Bicoid (Bcd) is distributed in an embryonic gradient that is critical for patterning the anterior-posterior (AP) body plan in Drosophila. Previous work identified several target genes that respond directly to Bcd-dependent activation. Positioning of these targets along the AP axis is thought to be controlled by cis-regulatory modules (CRMs) that contain clusters of Bcd-binding sites of different "strengths." Here we use a combination of Bcd-site cluster analysis and evolutionary conservation to predict Bcd-dependent CRMs. We tested 14 predicted CRMs by in vivo reporter gene assays; 11 show Bcd-dependent activation, which brings the total number of known Bed target elements to 21. Some CRMs drive expression patterns that are restricted to the most anterior part of the embryo, whereas others extend into middle and posterior regions. However, we do not detect a strong correlation between AP position of target gene expression and the strength of Bed site clusters alone. Rather, we find that binding sites for other activators, including Hunchback and Caudal correlate with CRM expression in middle and posterior body regions. Also, many Bcd-dependent CRMs contain clusters of sites for the gap protein Kruppel, which may limit the posterior extent of activation by the Bed gradient. We propose that the key design principle in AP patterning is the differential integration of positive and negative transcriptional information at the level of individual CRMs for each target gene.

Original languageEnglish (US)
Pages (from-to)4960-4965
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number14
DOIs
StatePublished - Apr 5 2005

Keywords

  • Morphogen
  • Network
  • Transcription

ASJC Scopus subject areas

  • General

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