Fig. 1. PAL-1 immunolocalization in par and mex-3 single and double mutant embryos. Strains mutant for the gene indicated above each column were injected with dsRNA as indicated to the left of each row (see Fig. 2A for quantitative summary of staining experiments). (A) Wild-type four-cell embryos express PAL-1 in the two posterior blastomeres. (B) par-3 embryos express PAL-1 in variable patterns, including in all four blastomeres, as shown. (C) par-1 and (D) par-4 embryos do not express PAL-1. (E-H) PAL-1 is expressed in all blastomeres of all double mutants that include mex-3(RNAi). We observed that par-4; mex-3 embryos often failed to complete early cell cycle events normally, including nuclear division and cytokinesis. (I) par-1; par-3(RNAi) embryos and (J) par-4; par-3(RNAi) embryos do not express PAL-1. (K) Working model for control of PAL-1 expression. par-3 restricts par-1 and par-4 activities to the posterior, where they inhibit mex-3 repression of PAL-1. In this and all subsequent figures, embryos are oriented anterior left and dorsal upwards when it is possible to determine polarity. Scale bar: 10 µm.
