37 research outputs found
Transcriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid
<p>Abstract</p> <p>Background</p> <p>Aphid adaptation to harsh winter conditions is illustrated by an alternation of their reproductive mode. Aphids detect photoperiod shortening by sensing the length of the night and switch from viviparous parthenogenesis in spring and summer, to oviparous sexual reproduction in autumn. The photoperiodic signal is transduced from the head to the reproductive tract to change the fate of the future oocytes from mitotic diploid embryogenesis to haploid formation of gametes. This process takes place in three consecutive generations due to viviparous parthenogenesis. To understand the molecular basis of the switch in the reproductive mode, transcriptomic and proteomic approaches were used to detect significantly regulated transcripts and polypeptides in the heads of the pea aphid <it>Acyrthosiphon pisum</it>.</p> <p>Results</p> <p>The transcriptomic profiles of the heads of the first generation were slightly affected by photoperiod shortening. This suggests that trans-generation signalling between the grand-mothers and the viviparous embryos they contain is not essential. By analogy, many of the genes and some of the proteins regulated in the heads of the second generation are implicated in visual functions, photoreception and cuticle structure. The modification of the cuticle could be accompanied by a down-regulation of the <it>N</it>-ÎČ-alanyldopamine pathway and desclerotization. In <it>Drosophila</it>, modification of the insulin pathway could cause a decrease of juvenile hormones in short-day reared aphids.</p> <p>Conclusion</p> <p>This work led to the construction of hypotheses for photoperiodic regulation of the switch of the reproductive mode in aphids.</p
Facultative Symbiont Infections Affect Aphid Reproduction
Some bacterial symbionts alter their hosts reproduction through various mechanisms that enhance their transmission in the host population. In addition to its obligatory symbiont Buchnera aphidicola, the pea aphid Acyrthosiphon pisum harbors several facultative symbionts influencing several aspects of host ecology. Aphids reproduce by cyclical parthenogenesis whereby clonal and sexual reproduction alternate within the annual life cycle. Many species, including the pea aphid, also show variation in their reproductive mode at the population level, with some lineages reproducing by cyclical parthenogenesis and others by permanent parthenogenesis. While the role of facultative symbionts has been well studied during the parthenogenetic phase of their aphid hosts, very little is known on their possible influence during the sexual phase. Here we investigated whether facultative symbionts modulate the capacity to produce sexual forms in various genetic backgrounds of the pea aphid with controlled symbiont composition and also in different aphid genotypes from natural populations with previously characterized infection status and reproductive mode. We found that most facultative symbionts exhibited detrimental effects on their hosts fitness under sex-inducing conditions in comparison with the reference lines. We also showed that the loss of sexual phase in permanently parthenogenetic lineages of A. pisum was not explained by facultative symbionts. Finally, we demonstrated that Spiroplasma infection annihilated the production of males in the host progeny by inducing a male-killing phenotype, an unexpected result for organisms such as aphids that reproduce primarily through clonal reproduction
Transcriptome Analysis of the Arabidopsis Megaspore Mother Cell Uncovers the Importance of RNA Helicases for Plant Germline Development
Germ line specification is a crucial step in the life cycle of all organisms. For sexual plant reproduction, the megaspore mother cell (MMC) is of crucial importance: it marks the first cell of the plant âgermlineâ lineage that gets committed to undergo meiosis. One of the meiotic products, the functional megaspore, subsequently gives rise to the haploid, multicellular female gametophyte that harbours the female gametes. The MMC is formed by selection and differentiation of a single somatic, sub-epidermal cell in the ovule. The transcriptional network underlying MMC specification and differentiation is largely unknown. We provide the first transcriptome analysis of an MMC using the model plant Arabidopsis thaliana with a combination of laser-assisted microdissection and microarray hybridizations. Statistical analyses identified an over-representation of translational regulation control pathways and a significant enrichment of DEAD/DEAH-box helicases in the MMC transcriptome, paralleling important features of the animal germline. Analysis of two independent T-DNA insertion lines suggests an important role of an enriched helicase, MNEME (MEM), in MMC differentiation and the restriction of the germline fate to only one cell per ovule primordium. In heterozygous mem mutants, additional enlarged MMC-like cells, which sometimes initiate female gametophyte development, were observed at higher frequencies than in the wild type. This closely resembles the phenotype of mutants affected in the small RNA and DNA-methylation pathways important for epigenetic regulation. Importantly, the mem phenotype shows features of apospory, as female gametophytes initiate from two non-sister cells in these mutants. Moreover, in mem gametophytic nuclei, both higher order chromatin structure and the distribution of LIKE HETEROCHROMATIN PROTEIN1 were affected, indicating epigenetic perturbations. In summary, the MMC transcriptome sets the stage for future functional characterization as illustrated by the identification of MEM, a novel gene involved in the restriction of germline fate
Deep sequencing on genome-wide scale reveals the unique composition and expression patterns of microRNAs in developing pollen of Oryza sativa
Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species
Background: The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M. persicae clonal lineages can colonise distantly related plants. This remarkable ability makes M. persicae a highly destructive pest of many important crop species. Results: To investigate the exceptional phenotypic plasticity of M. persicae, we sequenced the M. persicae genome and assessed how one clonal lineage responds to host plant species of different families. We show that genetically identical individuals are able to colonise distantly related host species through the differential regulation of genes belonging to aphid-expanded gene families. Multigene clusters collectively upregulate in single aphids within two days upon host switch. Furthermore, we demonstrate the functional significance of this rapid transcriptional change using RNA interference (RNAi)-mediated knock-down of genes belonging to the cathepsin B gene family. Knock-down of cathepsin B genes reduced aphid fitness, but only on the host that induced upregulation of these genes. Conclusions: Previous research has focused on the role of genetic adaptation of parasites to their hosts. Here we show that the generalist aphid pest M. persicae is able to colonise diverse host plant species in the absence of genetic specialisation. This is achieved through rapid transcriptional plasticity of genes that have duplicated during aphid evolution
4. -Améliorer la prévision locale des inondations : une démarche pragmatique de valorisation par les communes de l'information diffusée par les centres d'annonce des crues
L'amĂ©lioration de la prĂ©vision des crues et inondations pour la prise de dĂ©cision cm niveau de chaque commune demande que lâinformation soit adaptĂ©e aux caractĂ©ristiques locales.
La dĂ©marche de "valorisation de l'information" assure lâadĂ©quation entre ce besoin et l'information Ă©mise par les Services d' Annonce des Crues.
Cette démarche se concrétise par :
-la validation ou l'amélioration des caractéristiques de l'information diffusée par les services de l'Etat, qu'elles soient intrinsÚques (contenu des messages...) ou externes (présentation, vitesse de transmission...),
-l'Ă©laboration dâ "outils" permettant aux communes de prĂ©voir l'ampleur de l'inondation locale Ă partir des informations qui leur sont transmises.
Elle repose sur un processus de coopĂ©ration conjuguant les connaissances locales des communes, le savoir-faire des Services dâ Annonce des Crues et de Protection civile et l'expertise des hydrologues.
Cette prĂ©sentation sâappuie sur une expĂ©rience de terrain initiĂ©e par la DIREN Ile-de-France.Taliercio G., Le Trionnaire Y., Bouysses H., Godon Christine, Odier Michel, Roy Jean-Luc. 4. -AmĂ©liorer la prĂ©vision locale des inondations : une dĂ©marche pragmatique de valorisation par les communes de l'information diffusĂ©e par les centres d'annonce des crues. In: L'Ă©cole française de l'eau au service du dĂ©veloppement mondial. CongrĂšs de la SociĂ©tĂ© Hydrotechnique de France. 25Ăšmes journĂ©es de l'hydraulique. ChambĂ©ry, du 15 au 18 septembre 1996. Tome 1, 1998
POSTER 26 sCD14 in macrophages from patients with cystic fibrosis: Origin and involvement in inflammatory functions
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