Search results for "ductio"
showing 10 items of 13327 documents
Virus epidemics can lead to a population-wide spread of intragenomic parasites in a previously parasite-free asexual population
2014
Sexual reproduction is problematic to explain due to its costs, most notably the twofold cost of sex. Yet, sex has been suggested to be favourable in the presence of proliferating intragenomic parasites given that sexual recombination provides a mechanism to confine the accumulation of deleterious mutations. Kraaijeveld et al. compared recently the accumulation of transposons in sexually and asexually reproducing lines of the same species, the parasitoid wasp Leptopilina clavipes. They discovered that within asexually reproducing wasps, the number of gypsy-like retrotransposons was increased fourfold, whereas other retrotransposons were not. Interestingly, gypsy-like retrotransposons are cl…
Molecular markers linked to breeding system differences in segregating and natural populations of the cereal aphid Rhopalosiphum padi L.
1999
The aphid Rhopalosiphum padi shows coexistence of sexual and asexual populations, providing an opportunity to study the evolution of breeding system variation in the context of theories on the origin and maintenance of sex. However, assessments of the distribution of sexual and asexual lineages of this aphid are complicated by the difficulties in rapidly characterizing their breeding system. To facilitate this task and to gain insight into the genetic relatedness between sexual and asexual genotypes, molecular markers linked to breeding system differences were recently developed. In this study, we have successfully converted a random amplified polymorphic DNA (RAPD) marker associated with l…
EVALUATION OF ELEVATED PLOIDY AND ASEXUAL REPRODUCTION AS ALTERNATIVE EXPLANATIONS FOR GEOGRAPHIC PARTHENOGENESIS IN EUCYPRIS VIRENS OSTRACODS
2009
Transitions from sexual to asexual reproduction are often coupled with elevations in ploidy. As a consequence, the importance of ploidy per se for the maintenance and spread of asexual populations is unclear. To examine the effects of ploidy and asexual reproduction as independent determinants of the success of asexual lineages, we sampled diploid sexual, diploid asexual, and triploid asexual Eucypris virens ostracods across a European wide range. Applying nuclear and mitochondrial markers, we found that E. virens consists of genetically highly differentiated diploid sexual populations, to the extent that these sexual clades could be considered as cryptic species. All sexual populations wer…
The asexual enchytraeid worm Cognettia sphagnetorum (Oligochaeta) has increased Cu resistance in polluted soil
2001
We studied Cu resistance in the asexual (reproduction through fragmentation) enchytraeid worms (Cognettia sphagnetorum, Oligochaeta) originating from two sites: one uncontaminated, and another contaminated by heavy metals. Adult worms were smaller and population density was lower at the polluted site. However, adults from the contaminated site had better survival in Cu-contaminated soil, but lower survival as juveniles (fragments). As we do not know the genetic basis of Cu resistance of the worms, it may have been reached by acclimatization via induced Cu regulation. Because fragmentation is the only mode of reproduction, all phenotypic properties (including resistance) of a parental genera…
Introduction of Mysis relicta (Mysida) reduces niche segregation between deep-water Arctic charr morphs
2019
This is a post-peer-review, pre-copyedit version of an article published in Hydrobiologia. The final authenticated version is available online at https://doi.org/10.1007/s10750-019-3953-4. Niche diversification of polymorphic Arctic charr can be altered by multiple anthropogenic stressors. The opossum-shrimp (Mysis relicta) was introduced to compensate for reduced food resources for fish following hydropower operations in Lake Limingen, central Norway. Based on habitat use, stomach contents, stable isotopes (δ13C, δ15N) and trophically transmitted parasites, the zooplanktivorous upper water-column dwelling ‘normal’ morph was clearly trophically separated from two sympatric deep-water morphs…
A morphological and mitochondrial assessment of Apis mellifera from Palermo, Italy
1998
A characterization of the honey bees from western Sicily (Palermo, Italy) is presented. Mor- phological comparisons to A. m. ligustica were made using data taken from honey bee populations from southeastern (Bari) and central (Emilia Romagna) Italy. The honey bees of the Palermo area have distinct morphological differences compared to the mainland honey bees. The mtDNA haplotype common in subspecies within the African lineage of A. mellifera predominated in the Sicilian honey bee samples (13 out of 16). These results suggest both the potential and the desirability to expend efforts to conserve A. m. sicula. © Inra/DIB/AGIB/Elsevier, Paris
Involvement of plasma membrane proteins in plant defense responses. Analysis of the cryptogein signal transduction in tobacco
1999
International audience; Cryptogein, a 98 amino acid protein secreted by the fungus Phytophthora cryptogea, induces a hypersensitive response and systemic acquired resistance in tobacco plants (Nicotiana tabacum var Xanthi). The mode of action of cryptogein has been studied using tobacco cell suspensions. The recognition of this elicitor by a plasma membrane receptor leads to a cascade of events including protein phosphorylation, calcium influx, potassium and chloride effluxes, plasma membrane depolarization, activation of a NADPH oxidase responsible for active oxygen species (AOS) production and cytosol acidification, activation of the pentose phosphate pathway, and activation of two mitoge…
Acquired resistance triggered by elicitins in tobacco and other plants
1996
Elicitins are a family of proteins excreted byPhytophthora spp. They exhibit high sequence homology but large net charge differences. They induce necrosis in tobacco plants which then become resistant to the tobacco pathogenPhytophthora parasitica var.nicotianae. In stem-treated plants, resistance was not restricted to the site of elicitin application, but could be demonstrated by petiole inoculation at all levels on the stem. Resistance was already maximum after two days and lasted for at least two weeks. It was effective not only towardsP. p. var.nicotianae infection, but also against the unrelated pathogenSclerotinia sclerotiorum. In contrast to dichloroisonicotinic acid, an artificial i…
Type 2 histone deacetylases play a major role in the control of elicitor-induced cell death in tobacco
2011
article addendum : Bourque S, Dutartre A, Hammoudi V, Blanc S, Dahan J, Jeandroz S, Pichereaux C, Rossignol M, Wendehenne D., 2011. Type-2 histone deacetylases as new regulators of elicitorinduced cell death in plants. New Phytologist, 192 (1), 127–139. DOI: 10.1111/j.1469-8137.2011.03788.x; International audience; The cell death which characterizes the onset of the Hypersensitive Response (HR) is a very important weapon evolved by plants to block pathogen development. By the use of numerous plant/avirulent pathogen or plant/elicitor models, we have now obtained detailed signalling pathways allowing, after pathogen or elicitor perception, the control of the expression of specific sets of ge…
Preferential induction of 20S proteasome subunits during elicitation of plant defense reactions: towards the characterization of "plant defense prote…
2003
Plants have evolved efficient mechanisms to resist pathogens. The earliest defense response is the hypersensitive response (HR) considered as the main step leading to plant systemic acquired resistance (SAR) that protects the whole plant against a large spectrum of pathogens. We showed previously that elicitation of defense reactions in tobacco cells by cryptogein, a proteinaceous elicitor of plant defense reactions, leads to a rapid and differential accumulation of transcripts corresponding to genes encoding defense-induced (din) subunits of 20S proteasome: beta1din, alpha3din and alpha6din.Here, expression of these three subunits was investigated by Northern blotting and by Western blotti…