FIGURE 5.

miRNAs motifs are sufficient for let-7 expression. (A) In vivo reporter assays demonstrate that m3a is sufficient for seam cell GFP reporter (and thus miRNA) expression in adult worms. Of note, 52% of adult worms with wild-type (WT) let-7 enhancer transgene show GFP expression in the seam cells whereas no expression is seen with a control plasmid possessing no enhancer. The wild-type enhancer transgene was mutated uniquely for motif m2, m3a, and m3b or for motifs m3a and m3b together or jointly for all three motifs. Means with different letters are significantly different from each other (Wilcoxon sum rank tests P < 0.05). Error bars indicate ±1 standard error. (B) Example images show positive seam cell GFP expression in the wild-type enhancer strain (top) and m2 mutant strain (center), and negative seam cell GFP expression in a triple mutant (m2, m3a, m3b) strain. Maximum intensity projections of a Z series of fluorescent images are shown with (left column) or without (right column) a single DIC slice overlay. Seam cell GFP is shown in green; muscle mCherry signal (a co-injection marker) is shown in red.