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  • 1
    ISSN: 1570-7458
    Keywords: Cereal aphids ; Rhopalosiphum padi ; Sitobion avenae ; rate of increase ; fecundity ; alate ; apterous ; clone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Cette étude a eu pour but d'évaluer l'importance de facteurs intrinsèques (clone et morphe) sur les paramètres du taux d'accroissement de Sitobion avenae (F.) et Rhopalosiphum padi (L.). Pour chaque espèce, trois clones originaires de régions océaniques françaises ont été comparés à 20 °C pour les morphes exules ailés et exules aptères. L'effet du clone est significatif sur l'âge reproducteur (durée comprise entre la naissance du puceron et le début de sa phase de reproduction) et sur le taux intrinsèque d'accroissement naturel. Il est plus faible que celui du morphe avec lequel il intéragit dans le cas de R. padi. Les différences interspécifiques relevées mettent en évidence les capacités d'accroissement supérieures de R. padi par rapport à celles de S. avenae, dans le cas des ailés comme dans celui des aptères. Enfin, différents modèles ont été appliqués aux données de reproduction journalière des pucerons. Le type et la qualité des ajustements varient essentiellement en fonction du morphe.
    Notes: Abstract This study aimed at evaluating the influence of intrinsic factors (clone, morph) on the parameters of the intrinsic rate of increase of Sitobion avenae (F.) and Rhopalosiphum padi (L.). For each species, apterous and alate exules of three clones originating from French oceanic regions were compared at 20 °C. The clonal factor had a significant effect on both time from birth until onset of reproduction (TBR) and intrinsic rate of increase (r). This effect was lower than that of the morph. Moreover, in the case of R. padi, a strong clone-morph interaction was observed. Both apterous and alate morphs were shown to have a higher rate of increase in R. padi than in S. avenae. Various models were fitted to aphid daily rate of reproduction. Both types of model and quality of fit depended mainly on the morph.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2012-11-13
    Description: Background: The sequencing of the genome of the pea aphid Acyrthosiphon pisum revealed an unusual expansion of the miRNA machinery, with two argonaute-1, two dicer-1 and four pasha gene copies. In this report, we have undertaken a deeper evolutionary analysis of the phylogenetic timing of these gene duplications and of the associated selective pressures by sequencing the two copies of ago-1 and dcr-1 in different aphid species of the subfamily Aphidinae. We have also carried out an analysis of the expression of both copies of ago-1 and dcr-1 by semi-quantitative PCR in different morphs of the pea aphid life cycle. Results: The analysis has shown that the duplication of ago-1 occurred in an ancestor of the subfamily Aphidinae while the duplication of dcr-1 appears to be more recent. Besides, it has confirmed a pattern of one conserved copy and one accelerated copy for both genes, and has revealed the action of positive selection on several regions of the fast-evolving ago-1b. On the other hand, the semi-quantitative PCR experiments have revealed a differential expression of these genes between the morphs of the parthenogenetic and the sexual phases of Acyrthosiphon pisum. Conclusions: The discovery of these gene duplications in the miRNA machinery of aphids opens new perspectives of research about the regulation of gene expression in these insects. Accelerated evolution, positive selection and differential expression affecting some of the copies of these genes suggests the possibility of a neofunctionalization of these duplicates, which might play a role in the display of the striking phenotypic plasticity of aphids.
    Electronic ISSN: 1471-2148
    Topics: Biology
    Published by BioMed Central
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