Figure 4 SPTF-1 function in ASJ and conservation of the ASJ motif among C. elegans species. (A) Transgenic animals expressing GFP under control of the
sptf-1 promoter and TRX-1::DsRed under control of the
trx-1 promoter demonstrate ASJ colocalization (yellow color in the merged + bright-fieldimage). Bar, 20 um. (B, top) GFP expressed under control of the
sptf-1 promoter is found exclusively in ASJ neurons. (Bottom) ASJ, ASH, and ASK neurons are stained with the fluorescent DiI dye. Bar, 5 mm. (C) GFP expressed under control of the
sptf-1 promoter is found in other cell types such aspharyngeal cells, rectal cells, intestine, seam cells, and vulval cells. Bar, 20 mm (top and middle) and 100 mm (bottom). (D) RNAi downregulation of the endogenous
sptf-1 gene in a
rrf-3(
pk1426) sensitized background demonstrates that SPTF-1 is autoregulated. Bar, 20 um. (E)
sptf-1 RNAi downregulationdoes not interfere with ASJ neurogenesis while it impacts the expression of genes required for DiI uptake. Bar, 10 um. (F) Sequence alignment of the predicted ASJ motif found in the promoters of the
trx-1,
ssu-1 and
sptf-1 genes of several Caenorhabditis species define the ASJ motif, which is composed of two well-conserved 6 bp elements separated by a 3 bp more divergent linker sequence.