Title:
Molecular mechanism of biological timer to determine pupation timing during the prepupal period inDrosophila

Hitoshi Ueda
Laboratory of Molecular Mechanism of Developmental Control, The Graduate School of Natural Science and Technology, Okayama University, Japan

Abstract:
Occasionally, living organisms somehow determine the precise timing of their particular developmental events by measuring the period between two events during the process of their development. However, molecular mechanisms of time measuring systems by organisms are largely unknown, except for so-called clock systems. Determination mechanism of developmental timing regulated by ecdysone in fruit fly Drosophila provides one of the excellent model systems. At the onset of metamorphosis in D. melanogaster , a large pulse of ecdysone causes puparium formation, an event that larva suddenly transform its outside shape to pupa, and the following small ecdysone pulse induces pupation. At our standard rearing condition, pupation occurs 12 hours after puparium formation, suggesting that the fly is endowed with a biological timer to measure the time for pupation.
During the process to analyze how ecdysone signal transfers to developmental events at the prepupal period, we got evidences to show that two ecdysone inducible transcription factors Blimp-1 and FTZ-F1 play key roles in the process to determine pupation timing by controlling the timing of ecdysone pulse just before pupation. Furthermore, we found unique regulation mechanism of Blimp-1 expression to determine the precise timing of pupation. I will also discuss the importance of this time measuring system for the development of Drosophila .

References:
K. Akagi and H. Ueda, Regulatory mechanisms of ecdysone-inducible Blimp-1 encoding a transcriptional repressor that is important for the prepupal development in Drosophila. Dev Growth Differ. 53 697-703 (2011) .

Y. Agawa, M. Sarhan, Y. Kageyama, K. Akagi, M. Takai, K. Hashiyama, T. Wada, H. Handa, A. Iwamatsu , S. Hirose and H. Ueda, Drosophila Blimp-1 is a transient transcriptional repressor that controls timing of the ecdysone-induced developmental pathway. Mol. Cell. Biol. 27, 8739-8747 (2007)