Synthetic deconstruction of hunchback regulation by Bicoid

5 juil. 2021bioRxiv

DOI : 10.1101/2021.09.06.459125

Auteurs

Goncalo Fernandes, Huy Tran, Maxime Andrieu, Youssoupha Diaw, Carmina Perez-Romero, Cécile Fradin, Mathieu Coppey, Aleksandra M. Walczak, Nathalie Dostatni

Résumé

Abstract

For over 40 years, the Bicoid-hunchback (Bcd-hb) system in the fruit fly embryo has been used as the model to study how positional information in morphogen concentration gradients is robustly translated into step-like responses. A body of quantitative comparisons between theory and experiment have since questioned the initial paradigm that the sharp hb transcription pattern emerges solely from diffusive biochemical interactions between the Bicoid transcription factor and the gene promoter region. Several alternative mechanisms have been proposed, such as additional sources of positional information, positive feedback from Hb proteins or out-of-equilibrium transcription activation.

By using the MS2-MCP RNA-tagging system and analysing in real time, the transcription dynamics of synthetic reporters for Bicoid and/or its two partners Zelda and Hunchback, we show that all the hb expression pattern features and temporal dynamics are compatible with an equilibrium model with a short decay length Bicoid activity gradient as a sole source of positional information. Meanwhile, Bicoid’s partners speed-up the process by different means: Zelda lowers the Bicoid concentration threshold required for transcriptional activation while Hunchback reduces burstiness and increases the polymerase firing rate.

Membres

NATHALIE DOSTATNI

Sorbonne Université

MATHIEU COPPEY

Directeur de recherche CNRS