Abstract
Epidermal growth factor receptor (EGFR) plays an important role to the differentiation of cells in the Drosophila development. In stage 8 / 9 of Drosophila oogenesis, oocyte nuclear migrates from posterior to anterodorsal of egg chamber. The oocyte nuclear releases the ligand of EGFR-Gurken, which belongs to the TGF-α family of signaling molecules. Upon binding to the extracellular ligand, the EGFR induces a series of signal transduction, and then drosalizes the anterodorsal follicle cells. We want to screen the gene which acts in EGFR signaling pathway. We screened 756 P lines by X-Gal staining of Drosophila ovaries. We observed X-Gal staining of ovaries at stage 9 / 10. P360, P2319, and P1542 had positive X-Gal stainig in anterodorsal follicle cells at stage 9 / 10. We choose P360 for further study. We used in situ hybridization to prove that P360 RNA expression pattern is the same as X-Gal staining during stage 10. We found expanded P360 staining from stage 10 egg chamber of CY2Gal4 driven UAS-λtop4.2 females. The staining area was expaned to all follicle cells of egg chamber. This ectopic expression demonstrated that P360 is regulated by Egfr. The molecular cloning data of P360 demonstrated that P360 encoded an opening reading frame (ORF)-small transcript. The ORF is behind 308 bp of P360 insertion site. We received HS-small transcript fly which inserted {CaSpeR-hs} from Yang et al.,1999. Heat shock to this fly adult at 37℃can induce small transcript overexpression. We collected the eggs laid after heat shock and found that the respiratory appendages of the eggs were fused around the anterior of the eggs. This is a characteristic of dorsalization, which demonstrates that small transcript is a positive regulator of EGFR. We also calculated the interval from heat shock to the laid time. The result infers that small transcript is induced at the stage 8 / 9.