Figure 1. Flexon-based reagents for tissue-specific expression of TIR1 and for characterizing Cre and Flp recombinase excision patterns: A) A Flexon stop cassette is an artificial exon that contains stop codons and a frameshift generator (***), leading to termination of protein translation and nonsense-mediated decay of the transcript. Triangles represent recombinase target sites and the thin line represents intronic sequences flanking the artificial exon. For further information and considerations about Flexon design and placement see Shaffer and Greenwald (2022). B) TIR1(flexon) is expressed under the control of a strong ubiquitous promoter from
rps-27 (
rps-27p). In the absence of Cre, the Flexon cassette interrupts TIR1 translation after codon 159. In the presence of Cre, the Flexon is excised and the complete TIR1 protein is expressed under the control of
rps-27p. TIR1F79G(flexon) has an identical design to TIR1(flexon). C) The design of Cre and Flp testers was based on the design of arTi361[
rps-27p::GFP(flexon)::H2B::
unc-54 3'UTR] (Shaffer and Greenwald 2022). Nuclearly-localized GFP is expressed under the control of
rps-27p after excision in the presence of an appropriate Cre or Flp driver. H2B represents the sequence of a histone gene,
his-58. All transgenes reported in this study use the neutral
unc-54 3'UTR.