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. 2015 Jan 6;142(2):291–302. doi: 10.1242/dev.115147

Fig. 8.

Fig. 8.

MRG-1 sets up a threshold for proliferation and differentiation. White and grey bars represent hypothetical levels of GLD-1 GLD-2 pathway activity in the distal and proximal germ line, respectively. Dashed lines indicate a hypothetical threshold set by MRG-1 and the corresponding activity of factors controlled by MRG-1. Differentiation occurs if GLD-1 GLD-2 pathway levels are above the MRG-1 threshold and proliferation occurs if the pathway levels are below the threshold. In the wild type and in permissive glp-1(ar202gf) conditions, GLD-1 GLD-2 pathway levels are sufficient to promote differentiation in the proximal germ line, but not in the distal germ line, even though GLD-1 GLD-2 pathway levels are likely to be lower in glp-1(ar202gf) animals. In rfp-1(ok572) glp-1(ar202gf) animals, MRG-1 levels increase (due to decreased degradation), raising the threshold, such that proliferation occurs in the proximal end. In mrg-1(lf) animals (M–Z–), the threshold is lowered; therefore, even minimal levels of GLD-1 GLD-2 pathway activity promote differentiation.