1,720,972 research outputs found
Rickettsia Symbionts Cause Parthenogenetic Reproduction in the Parasitoid Wasp Pnigalio soemius (Hymenoptera: Eulophidae)
No full textBacteria in the genus Rickettsia are intracellular symbionts of disparate groups of organisms. Some Rickettsia strains infect vertebrate animals and plants, where they cause diseases, but most strains are vertically inherited symbionts of invertebrates. In insects Rickettsia symbionts are known to have diverse effects on hosts ranging from influencing host fitness to manipulating reproduction. Here we provide evidence that a Rickettsia symbiont causes thelytokous parthenogenesis ( in which mothers produce only daughters from unfertilized eggs) in a parasitoid wasp, Pnigalio soemius (Hymenoptera: Eulophidae). Feeding antibiotics to thelytokous female wasps resulted in production of progeny that were almost all males. Cloning and sequencing of a fragment of the 16S rRNA gene amplified with universal primers, diagnostic PCR screening of symbiont lineages associated with manipulation of reproduction, and fluorescence in situ hybridization ( FISH) revealed that Rickettsia is always associated with thelytokous P. soemius and that no other bacteria that manipulate reproduction are present. Molecular analyses and FISH showed that Rickettsia is distributed in the reproductive tissues and is transovarially transmitted from mothers to offspring. Comparison of antibiotic-treated females and untreated females showed that infection had no cost. Phylogenetic analyses of 16S rRNA and gltA gene sequences placed the symbiont of P. soemius in the bellii group and indicated that there have been two separate origins of the parthenogenesis-inducing phenotype in the genus Rickettsia. A possible route for evolution of induction of parthenogenesis in the two distantly related Rickettsia lineages is discussed
Ruolo di batteri simbionti nella riproduzione partenogenetica telitoca di Leptocybe invasa (Hymenoptera: Eulophidae)
No full textNo evidence of parthenogenesis-inducing bacteria involved in Thripoctenus javae thelytoky: an unusual finding in Chalcidoidea
No full textAll Hymenoptera have a haplodiploid mode of sex determination. Although most species reproduce by arrhenotokous parthenogenesis, there are many thelytokous species, in which unfertilized eggs develop into diploid females. Thelytoky can be genetic or due to microbial infection. In the large Chalcidoidea superfamily, thelytokous parthenogenesis is almost always associated with infection of endosymbionts of the genera Wolbachia, Cardinium, and Rickettsia. Thripoctenus javae (Girault) (Hymenoptera: Eulophidae) is a larval parasitoid of the greenhouse thrips Heliothrips haemorrhoidalis (Bouche) (Thysanoptera: Thripidae), an important worldwide pest. Both the host and its parasitoid reproduce by thelytokous parthenogenesis. The main goal of this study was to test whether endosymbiotic bacteria, either those known to induce thelytokous parthenogenesis or other sex-manipulators, are responsible for thelytoky of two geographically distinct populations of T. javae. We used sequencing of ribosomal ITS2 and 28S-D2 and mitochondrial COI genes to molecularly characterize the two populations, antibiotic and heat treatments, and FISH of ovaries, for thelytoky studies. It was impossible to revert thelytokous individuals back to sexual reproduction and no evidence of bacterial infection was found in parthenogenetic T. javae females. This makes T. javae the second chalcidoid in which thelytokous reproduction appears not to be associated with the presence of bacterial endosymbionts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
FUNGAL GENES INVOLVED IN PENTACHLOROPHENOL DEGRADATION
No full textHighly toxic compounds, as petroleum and its derivatives, solvents, alkanes, polycyclic
aromatic hydrocarbons (PAHs), pesticides, fertilizers, and heavy metals, released
constantly in the environment due to industrial andagricultural activities, are often highly
persistent and accumulate in the environment. Several strategies have been studied to
remediate polluted environments, based on physical, chemical, or biological methods
(Bioremediation). Well-known bioremediation agents include plants and microorganisms,
as well as their metabolites and enzymes. They have the potential to be exploited in
biotechnological application for bioremediation in a broad range of habitats and conditions.
Associations between diverse organisms may improve results significantly. Within our
collection, we selected a strain of the fungus Byssochlamys niveafor its ability to grow on
pentachlorophenol-contaminated soil. The use of this and other taxonomically related fungi
is strongly limited by the lack of biochemical and transcriptomic data on degradation
processes of recalcitrant organic pollutants. In addition, limited genomic reference data
discourage investigation on structural and functional diversity allowing this species to
interact with contaminants. In order to overpass the hole of sequence data to study genetic
basis of diversity in B. nivea, we generated a 3’-cDNA library and deeply sequenced it
using a Next Generation Sequencing approach. Assembling of reads resulted in 33,000
contigs and 37% of them showed a BLAST hit in the NCBI “nonredundant protein
sequence database”. The provided library is expected to encourage the use of B. niveaas a
model species for structural and functional investigation in genomics. Particularly, this
cDNA library could benefit biotechnological approaches aimed at investigating catabolic
processes involved in degradation of recalcitrant organic pollutants for development of
innovative bioremediation systems
Integration of molecular, ecological, morphological and endosymbiont data for species delimitation within the Pnigalio soemius complex (Hymenoptera: Eulophidae)
No full textIntegrative taxonomy is a recently developed approach that uses multiple lines of evidence such as molecular, morphological, ecological and geographical data to test species limits, and it stands as one of the most promising approaches to species delimitation in taxonomically difficult groups. The Pnigalio soemius complex (Hymenoptera: Eulophidae) represents an interesting taxonomical and ecological study case, as it is characterized by a lack of informative morphological characters, deep mitochondrial divergence, and is susceptible to infection by parthenogenesis-inducing Rickettsia. We tested the effectiveness of an integrative taxonomy approach in delimiting species within the P. soemius complex. We analysed two molecular markers (COI and ITS2) using different methods, performed multivariate analysis on morphometric data and exploited ecological data such as hostplant system associations, geographical separation, and the prevalence, type and effects of endosymbiont infection. The challenge of resolving different levels of resolution in the data was met by setting up a formal procedure of data integration within and between conflicting independent lines of evidence. An iterative corroboration process of multiple sources of data eventually indicated the existence of several cryptic species that can be treated as stable taxonomic hypotheses. Furthermore, the integrative approach confirmed a trend towards host specificity within the presumed polyphagous P. soemius and suggested that Rickettsia could have played a major role in the reproductive isolation and genetic diversification of at least two species
A revision of the Encarsia pergandiella species complex (Hymenoptera: Aphelinidae) shows cryptic diversity in parasitoids of whitefly pests
No full textEncarsia pergandiella Howard, described from North America (USA), and Encarsia tabacivora Viggiani, described from South America (Brazil) (Hymenoptera: Aphelinidae), are two formally recognized taxonomic entities, that have been treated by several authors as synonyms due to lack of strong diagnostic characters. Taxonomy of these species is further complicated because several populations, geographically separated and differing in their biology, have been included under the concept of E. pergandiella. Among these, a population originally collected in Brazil and introduced to North America reproduces by thelytokous parthenogenesis and is infected by the symbiont Cardinium, while a morphologically indistinguishable population, naturally occurring in Texas, is biparental and infected by a related strain of Cardinium that induces cytoplasmic incompatibility. A third population known from California and introduced to the Old World is biparental and uninfected by intracellular symbionts. While adult females of the first two populations have entirely light yellow bodies and pupate face up (light form), those of the third population have largely brown bodies and pupate face down (dark form). Other dark form populations are known from Texas, Florida and New York. Because these parasitoids are economically important biological control agents of cosmopolitan whitefly pests, it is critical to characterize them correctly. In this study, we integrated molecular and morphometric analyses to substantiate observed differences in biological traits, and resolve the complicated taxonomy of this species complex. We sequenced the mitochondrial cytochrome c oxidase subunit I gene and the D2 region of the ribosomal 28S gene for individuals of both light form (from Texas and Brazil) and dark form (from California, Texas, Italy and Canary Islands) originating from laboratory cultures or collected in the field. Phylogenetic analysis unambiguously distinguished three well-supported groups corresponding to the Texas light form, the Brazil light form and the dark form. Individuals of these three groups, in combination with all available type material (E. pergandiella, its synonym Encarsia versicolor Girault and E. tabacivora) and additional museum specimens of the dark form from New York and Italy, were subjected to multivariate morphometric analyses using Burnaby principal component analysis followed by a linear discriminant analysis, and multivariate ratio analysis. Overall, the analyses showed that: (i) E. pergandiella and E. tabacivora are two distinct species; (ii) the thelytokous Brazil light form corresponds to E. tabacivora; (iii) the biparental Texas light form is a new species formally described here as Encarsia suzannae sp.n.; (iv) two new biparental species can be referred to the dark form, one described as Encarsia gennaroi sp.n. including the populations sampled in California, Texas, Italy and Canary Islands, and the other corresponding to the population from New York described as Encarsia marthae sp.n. A dichotomous key for both sexes of the species of the E. pergandiella complex is provided for identification
- …
