Oogenesis in the suppressor2of Hairy‐wing mutant of Drosophila melanogaster. II. Nucleolar morphology and in vitro studies of RNA protein synthesis

Abstract

Cytological studies of ovaries from Drosophila melanogaster homozygous for the third chromosomal, female sterile gene, suppressor2 of Hairy‐wing (su2‐Hw), demonstrate that the nurse cell components of the egg chambers are primarily affected. Both chromosomes and nucleoli show qualitative and quantitative differencies from wild type. The in vitro culturing of mutant and wild type ovaries in the presence of labeled RNA and protein precursors were examined using liquid scintillation counting and autoradiography. The results of the scintillation experiments showed the mutant ovary to be nearly equivalent to wild type in the synthesis of RNA, but only half as active in protein synthesis. The autoradiographic analysis revealed that during very short incubation periods, the mutant ovary was more active than wild type in the production of RNA but that the mutant RNA was unstable. The lowered protein synthesis by mutant ovaries was also apparent using autoradiography. Morphometric measurements of mutant and wild type nurse nucleoli indicate a severe reduction in su2‐Hw compared to wild type. These findings suggest that the instability of mutant RNA may be due to some deficiency of the ribosomes produced in the absence of the su2‐Hw+ allele. On the other hand, the autoradiographic studies using H3‐uridine revealed the presence of an extranuclear label in the mutant nucleus not apparent in wild type. The possibility exists, therefore, that the unstable mutant RNA is of extranucleolar or…