Tyrosine phosphorylation accompanying the cellularization of the syncytial blastoderm of Drosophila.

At an early stage in embryogenesis, the Drosophila blastoderm is a syncytium in which approximately 6000 nuclei align under the plasma membrane. During the interphase of nuclear cycle 14, a wave of membrane formation descends from the blastoderm surface to enclose each nucleus in an intact cell membrane. We show by immunofluorescence microscopy that the membrane-formation process is closely accompanied in space and time by a wave of tyrosine phosphorylation, suggesting that one or more tyrosine kinases and phosphatases are active in the process.