String of Pearls Encodes Drosophila Ribosomal Protein S2, Has Minute-like Characteristics, and Is Required during Oogenesis

The first allele of string of pearls (sop) was isolated as a recessive female sterile mutant in a P element enhancer trap screen. Oogenesis in homozygous sop females arrests at approximately stage 5. In addition, homozygous flies of both sexes have Minute-like characteristics that include reduced bristles, delayed development and larval lethality. sop maps to 30D/E on chromosome 2L and encodes the Drosophila homolog of eukaryotic ribosomal protein S2. The gene is present in a single copy in the Drosophila genome and the level of mRNA present in mutant animals is reduced. The identification of a mutant allele that blocks development at a mid-stage of oogenesis may indicate that sop has a specific developmental role during oogenesis in addition to its general role in protein synthesis as a component of the small ribosomal subunit.