A quantitative analysis of the kinetics of Gal4 activator and effector gene expression in the zebrafish.

Using a temperature-inducible hsp70:Gal4 activator and UAS:myc-notch1a-intra as effector, we determined quantitatively the kinetics of expression of both transgenes and analysed the effects of varying their expressivity on several phenotypic traits in the developing zebrafish. hsp70:Gal4 is transcribed within 15 min after temperature-mediated induction, but Gal4 RNA decays rapidly. The Gal4 protein was found to be quite stable, as functional Gal4, which was detectable 1.5 h after heat shock (HS), persisted for at least 13 h. myc-notch1a-intra RNA is expressed approximately 1.5 h after HS, but unlike the Gal4 RNA, it was found to be very stable; it continues to accumulate during the succeeding 17 h after HS. Fully penetrant phenotypic effects are obtained after a relatively long activator induction with a 30-min HS.