Heritable Endosymbionts of Drosophila

Abstract

Although heritable microorganisms are increasingly recognized as widespread in insects, no systematic screens for such symbionts have been conducted in Drosophila species (the primary insect genetic models for studies of evolution, development, and innate immunity). Previous efforts screened relatively few Drosophila lineages, mainly for Wolbachia. We conducted an extensive survey of potentially heritable endosymbionts from any bacterial lineage via PCR screens of mature ovaries in 181 recently collected fly strains representing 35 species from 11 species groups. Due to our fly sampling methods, however, we are likely to have missed fly strains infected with sex ratio-distorting endosymbionts. Only Wolbachia and Spiroplasma, both widespread in insects, were confirmed as symbionts. These findings indicate that in contrast to some other insect groups, other heritable symbionts are uncommon in Drosophila species, possibly reflecting a robust innate immune response that eliminates many bacteria. A more extensive survey targeted these two symbiont types through diagnostic PCR in 1225 strains representing 225 species from 32 species groups. Of these, 19 species were infected by Wolbachia while only 3 species had Spiroplasma. Several new strains of Wolbachia and Spiroplasma were discovered, including ones divergent from any reported to date. The phylogenetic distribution of Wolbachia and Spiroplasma in Drosophila is discussed.

The Molecular Basis of Host Adaptation in Cactophilic Drosophila: Molecular Evolution of a GlutathioneS-Transferase Gene (GstD1) inDrosophila mojavensis

“…No sex-specific dispersal rates were previously observed in D. mojavensis, but this was examined only in one of the four populations (Markow and Castrezana 2000). Spiroplasma endosymbionts have been found in D. mojavensis (Mateos et al 2006), although the nature of this interaction has not been resolved. These discrepancies in results between nuclear and mitochondrial genes warrant future examination.…”

The 19 Genomes of Drosophila: A BAC Library Resource for Genus-Wide and Genome-Scale Comparative Evolutionary Research

“…and Spiroplasma spp.) at least five adult fly DNA samples from each species were screened with established protocols (Mateos et al 2006). Finally, species identity was confirmed by both morphological and molecular approaches.…”

Male killing Spiroplasma protects Drosophila melanogaster against two parasitoid wasps

“…To identify potential heritable endosymbionts of these flies, at least three females per isoline were subjected to sterile ovary dissection and DNA extraction as described in Mateos et al (2006). Three sets of universal polymerase chain reaction (PCR) primer screenings were then conducted on the DNA extracts: (1) primers for bacterial 16S rRNA gene (10F-1507R); (2) primers for bacterial 16S rRNA gene (27F-1495R); and (3) primers for 16S-23S rRNA gene fragment (559F-35R).…”