Fig. 1

Cre-mediated recombination in the red-to-green reporter line.

(a) Scheme of the recombination event. In the absence of Cre the EF1α promoter drives the expression of DsRed2 but changes to EGFP after successful Cre-mediated recombination. (b) Embryos of the red-to-green reporter line show strong DsRed2 and no EGFP fluorescence. (c) Maternal contribution of the Tg(hsp70:EGFP-Cre) allele results in complete loss of DsRed2 and ubiquitous EGFP expression in double transgenic embryos. (d) Paternal contribution of the Tg(hsp70:EGFP-Cre) allele leads to strong DsRed2 and mosaic EGFP expression in double transgenic embryos. (e) Paternal contribution of the Tg(hsp70:EGFP-Cre) allele and brief heat induction at mid-gastrulation stages results in reduced DsRed2 and strong ubiquitous EGFP expression in double transgenic embryos. (f) Embryos of the Tg(hsp70:EGFP-Cre) line show only weak EGFP fluorescence after brief heat induction at mid-gastrulation stages. b–f Lateral views of live 24 hpf embryos bearing different transgenes. Scale bar, 125 μm.