Figure 5. Characterization of
mex-5(T186A);
mex-6(RNAi) and PLK-1::sGFP Embryos(A) Schematic of MEX-5(T186A).(B-D) GFP::POS-1 localization (B), relative concentration along the A/P axis (C), and FRAP curves (D) in embryos of the indicated genotype. GFP::POS-1 FRAPcurves are similar in control RNAi and
mex-6(RNAi) embryos (see Figure S5A).(E) Mean
t1/2 for the indicated FRAP experiments.(F) PLK-1::sGFP localization in WT and
mex-5/6(RNAi) embryos. Top: duplicate images with different intensity normalizations (dim and bright). The centrosomaland chromosomal signals in the bright images are saturated. Bottom: the concentration of PLK-1::sGFP in the cytoplasm is not affected by
mex-5/6(RNAi).(G) Relative concentration of PLK-1::sGFP along the A/P axis (normalized to the posterior end).(H) FRAP curves for PLK-1::sGFP in wild-type and
mex-5/6(RNAi) embryos.(I) Working model. MEX-5 (red) and POS-1 (green) exist in fast-diffusing complexes and slow-diffusing complexes. The interaction of both MEX-5 and POS-1 withslow-diffusing complexes depends on their ability to bind RNA. PAR-1 phosphorylation of MEX-5 (depicted as ''+P'') inhibits the formation of slow-diffusing MEX-5complexes in the posterior, leading to their enrichment in the anterior. PLK-1 phosphorylation of POS-1 inhibits the formation of slow-diffusing POS-1 complexes inthe anterior, where PLK-1 most likely accumulates in slow-diffusing RNA complexes due to its interaction with MEX-5, which was shown by yeast two hybrid [23]. Asa consequence, slow-diffusing POS-1 complexes accumulate in the posterior, giving rise to the POS-1 concentration gradient. PLK-1 is depicted as inhibitingPOS-1 association with slow-diffusing complexes for simplicity, but it could also promote POS-1 dissociation from slow-diffusing complexes.See also Figures S3 and S5 and Table S1.