Construction and expression of the <i>r-opsin1::egfp-f2a-ntr transgene</i>.

<p>(A) Schematized generation of the <i>r-opsin1::egfp-f2a-ntr</i> construct. The <i>egfp-f2a-ntr</i> cassette was recombined into the <i>Platynereis </i><i>r-opsin1</i> locus by homologous recombination. 8kbps of the surrounding genomic locus plus cassette were PCR amplified and subcloned into the mariner transposon vector used for transgenesis. (B-D) Co-expression of <i>egfp</i> and <i>ntr</i> in the adult eye photoreceptors of <i>r-opsin1::egfp-f2a-ntr</i> stable transgenic worms. (B) eGFP fluorescence demarcating the adult eye photoreceptors and their projections in stable <i>r-opsin1::egfp-f2a-ntr</i> transgenic worms. (C) Expression of <i>nitroreductase</i> (red) in the same cell type as visualized by whole mount in situ hybridization (WMISH) using <i>nitroreductase</i> antisense riboprobe. (D) Co-staining with <i>nitroreductase</i> (detected in red) and <i>egfp</i> (detected in blue) riboprobes results in purple color, indicative of faithful co-expression of both genes in the adult eye photoreceptors. ae- adult eyes; arrowheads point at expressing cells; arrow points at axonal projection of PRCs; asterisks- head pigment cells which show autofluorescence in the channel used for eGFP documentation. Scale bar: 20µm.