TY - JOUR T1 - A re-inducible genetic cascade patterns the anterior-posterior axis of insects in a threshold-free fashion JF - bioRxiv DO - 10.1101/321786 SP - 321786 AU - Alena Boos AU - Jutta Distler AU - Heike Rudolf AU - Martin Klingler AU - Ezzat El-Sherif Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/05/15/321786.abstract N2 - Gap genes mediate the division of the anterior-posterior axis of insects into different fates through regulating downstream hox genes. Decades of tinkering the segmentation gene network of the long-germ fruit fly Drosophila melanogaster led to the conclusion that gap genes are regulated (at least initially) through a threshold-based French Flag model, guided by both anteriorly- and posteriorly-localized morphogen gradients (bicoid and caudal, respectively). In this paper, we show that the expression patterns of gap genes in the intermediate-germ beetle Tribolium castaneum are mediated by a self-regulatory and threshold-free ‘Speed Regulation’ mechanism, guided by a posterior gradient of the transcription factor caudal. We show this by re-inducing the gap gene cascade at arbitrary points in time by simply re-inducing the leading gene in the gap gene cascade (namely, hunchback). This demonstrates that the gap gene network is self-regulatory and is primarily under the control of a posterior morphogen in short- and intermediate-germ insects. ER -