Figure 6. LIN-39 is continuously required to control expression of terminal identity genes.

(A) Animals of the lin-39::mNG::3xFLAG::AID; eft-3::TIR1 genotype were either administered ethanol (EtOH) or auxin at the L3 stage. Twenty four hours later, expression of endogenous lin-39 reporter (lin-39::mNG::3xFLAG::AID) is severely reduced in the nuclei of VNC MNs (arrowheads) at the young adult stage (day 1). mNG green fluorescent signal is shown in white for better contrast. White dotted line indicates the boundary of intestinal tissue (gut), which tends to be autofluorescent in the green channel. (B) Quantification of number of MNs expressing the lin-39::mNG::3xFLAG::AID reporter after EtOH (control) and auxin treatment. N > 14. ***p<0.001. (C) Schematic showing time window of auxin administration. (D–F) Auxin or ethanol (control) were administered at larval stage 4 (L4) on unc-3 (n3435); lin-39::mNG::3xFLAG::AID; eft-3::TIR1 animals carrying either the VD marker ser-2::gfp, the VC marker glr-5::gfp, or the VD/VC marker flp-11::gfp. Images were taken at the young adult stage (day 1.6 for ser-2, day 1.8 for glr-5 and day two for flp-11). A significant decrease in the number of MNs expressing the VD marker was evident in the auxin-treated animals compared to EtOH-treated controls. For comparison, quantification of marker expression is also provided in unc-3 (n3435) mutants. We note that hypomorphic effects in the ethanol treated group have been previously reported for other AID-tagged TFs in C. elegans (Kerk et al., 2017). Such effects appear to be target gene-specific, as they were observed for glr-5 and flp-11, but not ser-2 (Figure 6E–F). N > 15. **p<0.01, ***p<0.001, N. S: not significant.