Cloning and characterization of a gene encoding glutathione-regulated potassium-efflux system protein KefKL from the endosymbiont Wolbachia.

The maternally inherited intracellular symbiont Wolbachia is well known for inducing a variety of reproductive and developmental abnormalities in the diverse arthropod hosts it infects. It has been implicated in causing cytoplasmic incompatibility (CI), parthenogenesis, feminization of genetic males and male killing in different hosts. However, the molecular mechanisms by which this fastidious bacterium causes these abnormalities have not yet been determined. In our study, representational difference analysis (RDA) was used to analyze the genomic difference between different Wolbachia strains. A gene encoding glutathione-regulated potassium-efflux system protein KefKL from Wolbachia in Drosophila simulans Riverside (w Ri) was isolated. The homologous genes from Wolbachia in Drosophila melanogaster yw67c23 (wMel) and Wolbachia in Drosophila melanogaster CantonS (wMelCS) were also cloned and sequenced. Sequence analysis showed that these deduced amino acid sequences contained two important motifs: Na+/H+ antiportor and NAD binding domain, which shared conserved sequences among different strains. Considering the crucial function of KefKL for ionic homeostasis, this gene might play an important role in Wolbachia physiology. Further study indicated that there was no homologue detected from Wolbachia in Drosophila simulans DSW/Mau (wMa) and Wolbachia in Drosophila simulans Noumea (wNo). Whether Wolbachia contained KefKL (or the homologous gene) was consistent with the phylogenetic studies using wsp sequences, which showed that wMa and wNo were grouped into one branch, while w Ri, wMel and wMelCS were more closely related.