Translational control determines spatial distribution of E74A protein.

<p>Tissues at the onset of metamorphosis were dissected and imaged to detect <i>E74A</i> mRNA (in red, first column), E74A protein (in red, second through fifth columns) or Belle protein (in green, fifth column). Although ecdysone-induced transcription of <i>E74A</i> mRNA appears to be ubiquitously expressed (first column), E74A protein is not (second column). This spatial distribution of E74A protein is disrupted in <i>bel^psg9</i> mutant animals (third column) and becomes ubiquitous after expression of E74A protein from the <i>hs-E74A</i> transgene (fourth column). E74A protein is detected in the large cells of the proventriculus (G) and <i>repo</i>-positive glial cells in the ventral nerve cord (L and data not shown), but absent in the entire imaginal wing discs (B), the imaginal ring of the proventriculus (G) and neurons in the ventral nerve cord (L). Endogenous Belle protein, visualized with the <i>bel^GFP-ZCL1911</i> exon trap, is expressed in all cells including those that do not express E74A protein (fifth column). Staining with antibodies directed to Belle protein show identical expression patterns (data not shown). For <i>in situ</i> hybridizations, tissues were dissected from animals a few hours before puparium formation (clear gut stage) when <i>E74A</i> mRNA levels are their highest. For E74A protein and BEL-GFP imaging, tissues were dissected at puparium formation when E74A protein levels are at their highest. DAPI costained nuclei in blue. WD: imaginal wing discs, PV: proventriculus, VNC: ventral nerve cords.