In the absence of supplemental zinc, transgenic animals displayed low level, variable
mtl-1::GFP expression in the pharynx and no detectable GFP expression in intestinal cells. By contrast, in the presence of 200 uM supplemental zinc, worms displayed strong GFP expression in intestinal cells, whereas pharyngeal expression levels were not altered. Quantitative analysis using qRT-PCR showed that GFP mRNA levels were increased ~70-fold in response to 200 uM supplemental zinc compared to 0 uM supplemental zinc.