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 15min after temperature-mediated induction, but Gal4 RNA decays rapidly. The Gal4 protein was found to be quite stable, as functional Gal4, which was detectable 1.5h after heat shock (HS), persisted for at least 13h. myc-notch1a-intra RNA is expressed approximately 1.5h after HS, but unlike the Gal4 RNA, it was found to be very stable; it continues to accumulate during the succeeding 17h after HS. Fully penetrant phenotypic effects are obtained after a relatively long activator induction with a 30-min HS.