Fig. 2. The mnk mutation suppresses zygotic gene transcription and Cdc2-phosphorylation defects in grp mutant embryos. (A,B) Whole-mount in situ hybridization of the segmentation gene runt (A) and the cellularization gene serendipity- (B). (A) Control (w¹¹¹⁸) and mnk-null mutant embryos show seven-stripe runt transcript expression during interphase 14. The runt gene is never expressed at high levels in grp-null mutant embryos. By contrast, seven-stripe runt expression is clearly observed in mnk grp double-null mutant embryos. (B) serendipity- is required for cellularization and is expressed at high levels during interphase 14 in both wild-type (w¹¹¹⁸) and mnk mutant embryos, but not in grp mutant embryos. Expression of serendipity- is also restored in mnk grp double mutants. (C) In control (w¹¹¹⁸) and mnk mutants, inhibitory tyrosine phosphorylation of Cdc2 dramatically increases at the MBT, between 2 and 4 hours post-egg-deposition. This dramatic increase in Cdc2 phosphorylation is not observed in grp mutant embryos. In mnk grp double-mutant embryos, however, essentially wild-type Cdc2 phosphorylation is restored (at 2-3 and 3-4 hours). Western blots of embryonic lysates were probed with antibodies against phospho-Cdc2 (Tyrosine 15), and -Tubulin was used as the loading control. Embryo age in hours is indicated (0-1,1-2, 2-3 and 3-4). Scale bars: 100 µm.