Expression of cytoplasmic incompatibility in Drosophila simulans and its impact on infection frequencies and distribution of Wolbachia pipientis

The aim of this study is to examine the expression of cytoplasmic incompatibility and investigate the distribution and population frequencies of Wolbachia pipientis strains in Drosophila simulans. Nucleotide sequence data from 16S rDNA and a Wolbachia surface protein coding sequence and cytoplasmic incompatibility assays identify four distinct Wolbachia strains: wHa, wRi, wMa, and wAu. The levels of cytoplasmic incompatibility between six lines carrying these strains of bacteria and three control lines without bacteria are characterized. Flies infected with wHa and wRi are bidirectionally incompatible, and males that carry either strain can only successfully produce normal numbers of offspring with females carrying the same bacterial strain. Males infected with wAu do not express incompatibility. Males infected with the wMa strain express intermediate incompatibility when mated to females with no bacteria and no incompatibility with females with any other Wolbachia strain. We conduct polymerase chain reaction/restriction fragment length polymorphism assays to distinguish the strain of Wolbachia and the mitochondrial haplotype to survey populations for each type and associations between them. Drosophila simulans is known to have three major mitochondrial haplotypes (siI, sill, and siIII) and two subtypes (siIIA and siIIB). All infected lines of the sil haplotype carry wHa, wNo, or both; wMa and wNo are closely related and it is not clear whether they are distinct strains or variants of the same strain. Infected lines with the silIA haplotype harbor wRi and the siIIB haplotype carries wAu. The wMa infection is found in siIII haplotype lines. The phenotypic expression of cytoplasmic incompatibility and its relation to between-population differences in frequencies of Wolbachia infection are discussed.     

Evolution and biogeography of the woody Hawaiian violets (Viola, Violaceae): arctic origins, herbaceous ancestry and bird dispersal

Specialists studying the genus Viola have consistently allied the Hawaiian violets comprising section Nosphinium--most of which are subshrubs or treelets--with putatively primitive subshrubs in certain South American violet groups. Hawaiian violets also possess inflorescences, a floral disposition otherwise found only in other genera of the Violaceae, thus strengthening the hypothesis of a very ancient origin for the Hawaiian species. A survey of phylogenetic relationships among infrageneric groups of Viola worldwide using nuclear rDNA internal transcribed spacer (ITS) sequences revealed a dramatically different biogeographic origin for the Hawaiian violets: A monophyletic Hawaiian clade was placed in a close sister relationship with the amphi-Beringian tundra violet, V. langsdorffii s. 1., in a highly derived position. This remarkable and unforeseen relationship received strong clade support values across analyses, and monophyly of the Hawaiian lineage was further indicated by a unique 26-base-pair deletion in section Nosphinium. The high polyploid base chromosome number (n approximately equal to 40) in the Hawaiian violets relates them to Alaskan and eastern Siberian populations in the polyploid V. langsdorffii complex. More than 50 species of the 260 allochthonous birds wintering in the Hawaiian Islands are found to breed in the Arctic, occupying habitats in which individual birds might have encountered ancestral V. langsdorffii populations and served as dispersers to the central Pacific region. Acquisition of derived morphological traits (e.g., arborescence and inflorescences), significance of a confirmed Arctic origin for a component of the Hawaiian flora, and the likelihood of other "cryptic" Arctic elements in the Hawaiian flora deserving independent molecular phylogenetic corroboration are discussed.     

Mitochondrial DNA variants influence mitochondrial bioenergetics in Drosophila melanogaster

The influence of mitochondrial DNA (mtDNA) mutations on human disease has been extensively studied, but the impact of mutations within the adaptive range is debated. We studied males from lines of Drosophila melanogaster that have a highly standardized nuclear genome but different mtDNA, at two ages. We measured mitochondrial respiration on permeabilized muscle fibers, hydrogen peroxide production of isolated mitochondria and mtDNA copy number of whole individuals. The results show that a small set of naturally occurring mtDNA mutations can have a significant influence on mitochondrial bioenergetics that may change as the organism ages.     

Electrokinetic-enhanced phytoremediation of uranium-contaminated soil using sunflower and Indian mustard

Abstract

Electrokinetic-enhanced phytoremediation is an effective technology to decontaminate heavy metal contaminated soil. In this study, we examined the effects of electrokinetic treatments on plant uptake and bioaccumulation of U from soils with various U sources. Redistribution of uranium in soils as affected by planting and electrokinetic treatments was investigated. The soil was spiked with 100?mg kg^–1 UO₂, UO₃, and UO₂(NO₃)₂. After sunflower and Indian mustard grew for 60 days, 1 voltage of direct-current was applied across the soils for 9 days. The results indicated that U uptake in both plants were significantly enhanced by electrokinetic treatments from soil with UO₃ and UO₂(NO₃)₂. U was more accumulated in roots than in shoots. Electrokinetic treatments were effective on lowering soil pH near the anode region. Overall, uranium (U) removal efficiency reached 3.4–4.3% from soils with UO₃ and uranyl with both plants while that from soil with UO₂ was 0.7–0.8%. Electrokinetic remediation treatment significantly enhanced the U removal efficiency (5–6%) from soils with UO₃ and uranyl but it was 0.8–1.3% from soil with UO₂, indicating significant effects of U species and electrokinetic enhancement on U bioaccumulation. This study implies the potential feasibility of electrokinetic-enhanced phytoremediation of U soils with sunflower and Indian mustard.