GAP-JUNCTIONS IN OVARIAN FOLLICLES OF DROSOPHILA-MELANOGASTER - INHIBITION AND PROMOTION OF DYE-COUPLING BETWEEN OOCYTE AND FOLLICLE CELLS

The analysis of chimeras has shown that communication between germ-lin e and soma cells plays an important role during Drosophila oogenesis. We have therefore investigated the intercellular exchange of the fluor escent tracer molecule, Lucifer yellow, pressure-injected into the ooc yte of vitellogenic follicles of Drosophila. The dye reached the nurse cells via cytoplasmic bridges and entered, via gap junctions, the som atic follicle cells covering the oocyte. The percentage of follicles s howing dye-coupling between oocyte and follicle cells was found to inc rease with the developmental stage up to stage 11, but depended also o n the status of oogenesis, i.e., the stage-spectrum, in the respective ovary. During late stage 10B and stage 11, dye-coupling was restricte d to the follicle cells covering the anterior pole of the oocyte. No d ye-coupling was observed from stage 12 onwards. During prolonged incub ation in vitro, the dye was found to move from the follicle cells back into the oocyte; this process was suppressable with dinitrophenol. Dy e-coupling was inhibited when prolonged in vitro incubation preceded t he dye-injection. Moreover, dye-coupling was inhibited with acidic pH, low [K+], high intracellular [Ca2+], octanol, dinitrophenol, and NaN3 , but not with retinoic acid, basic pH, or high extracellular [Ca2+]. Dye-coupling was stimulated with a juvenile hormone analogue and with 20-hydroxyecdysone. Thus, gap junctions between oocyte and follicle ce lls may play an important role in intercellular communication during o ogenesis. We discuss the significance of our findings with regard to t he electrophysiological properties of the follicles, and to the coordi nated activities of the different cell types during follicle developme nt and during the establishment of polarity in the follicle.