Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Rapid cold hardening (RCH) is a form of thermal acclimation that allows ectotherms to fine-tune their physiological state to match rapid changes in thermal environment. Despite progress in recent years, there is still a considerable uncertainty regarding the physiological basis of RCH in insects. Here we investigated the physiological response of adult Drosophila melanogaster to a gradual reduction of temperature from 25 to 0°C followed by 1h at 0°C. As expected, this RCH treatment promoted cold tolerance, and so we hypothesized that this change could be detected at the proteomic level. Using 2D-DIGE, we found that only a few proteins significantly changed in abundance, and of these, we identified a set of four proteins of particular interest. These were identified as two different variants of glycogen phosphorylase (GlyP) of which three spots were up-regulated and another was down regulated. In subsequent experiments, we quantified upstream events by measuring the GlyP mRNA amount, but we found no marked effect of RCH. We also examined downstream events by measuring GlyP activity and the level of free sugars. We found no effect of RCH on GlyP activity. On the other hand, screening of whole animal sugar contents revealed a small increase in glucose levels following RCH while trehalose content was unaltered. This study highlights a complex regulation of GlyP in relation to RCH where we found associations between the cold tolerance, the protein abundance and the metabolite concentrations but no changes in mRNA expression and enzyme activity. These data stress the necessity of combining the hypothesis-generating power of an 'Omics' approach with subsequent targeted validations across several levels of the biological organization. We discuss reasons why different biological linked levels do not necessarily change stoichiometrically.
ISSN: 0022-1910

hal-00991032
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00991032
DOI : 10.1016/j.jinsphys.2014.01.009
PUBMED : 24508557

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Thermal acclimation drastically alters thermotolerance of ectotherms, but the mechanisms determining this plastic response are not fully understood. The present study investigates the proteomic response (2D-DIGE) of adult Drosophila melanogaster acclimated at 11, 25 or 31 C. As expected 11 C-acclimation improved cold tolerance and 31 C-acclimation improved heat tolerance. We hypothesized that the marked organismal responses to acclimation could be detected at the proteomic level assuming that changes in the abundance of specific proteins are linked to the physiological changes underlying the phenotypic response. The 31 C-acclimated flies displayed a particular divergent proteomic profile where molecular chaperones made up a large number of the proteins that were modulated during heat acclimation. Many other proteins showed significant modulation during acclimation including proteins involved in iron ion and cell redox homeostasis, carbohydrate and energy metabolism, chromatin remodeling and translation, and contractile machinery. Interestingly the changes in protein abundance were often unrelated to transcriptional activity of the genes coding for the proteins, except for the most strongly expressed proteins (e.g. Hsp70). The 11 C-acclimation evoked weak proteomic response despite the marked effect on the organismal phenotype. Thus the acquired cold tolerance observed here may involve regulatory process such as posttranslational regulation rather than de novo protein synthesis.
ISSN: 0965-1748

hal-00826939
https://hal.archives-ouvertes.fr/hal-00826939
DOI : 10.1016/j.ibmb.2013.01.006
PUBMED : 23416132

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The common endosymbiotic Wolbachia bacteria influence arthropod hosts in multiple ways. They are mostly recognized for their manipulations of host reproduction, yet, more recent studies demonstrate that Wolbachia also impact host behavior, metabolic pathways and immunity. Besides their biological and evolutionary roles Wolbachia are new potential biological control agents for pest and vector management. Importantly, Wolbachia-based control strategies require controlled symbiont transfer between host species and predictable outcomes of novel Wolbachia-host associations. Theoretically, this artificial horizontal transfer could inflict genetic changes within transferred Wolbachia populations. This could be facilitated through de novo mutations in the novel recipient host or changes of haplotype frequencies of polymorphic Wolbachia populations when transferred from donor to recipient hosts. Here we show that Wolbachia resident in the European cherry fruit fly, Rhagoletis cerasi, exhibit ancestral and cryptic sequence polymorphism in three symbiont genes, which are exposed upon microinjection into the new hosts Drosophila simulans and Ceratitis capitata. Our analyses of Wolbachia in microinjected D. simulans over 150 generations after microinjection uncovered infections with multiple Wolbachia strains in trans-infected lines that had previously been typed as single infections. This confirms the persistence of low-titer Wolbachia strains in microinjection experiments that had previously escaped standard detection techniques. Our study demonstrates that infections by multiple Wolbachia strains can shift in prevalence after artificial host transfer driven by either stochastic or selective processes. Trans-infection of Wolbachia can claim fitness costs in new hosts and we speculate that these costs may have driven the shifts of Wolbachia strains that we saw in our model system.
ISSN: 1932-6203

hal-01544765
https://hal.archives-ouvertes.fr/hal-01544765
DOI : 10.1371/journal.pone.0082402

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Le territoire d’Aysen, au sud du Chili, officiellement dénommé « Région XI », possède le charme discret d’une Patagonie oubliée. Cette région mythique n’a cessé de hanter l’imaginaire fécond des découvreurs et voyageurs en tout genre. Aujourd’hui, ces derniers sont autant des pêcheurs à la mouche fortunés que des routards européens ou israéliens, et de plus en plus des Chiliens venus des classes moyennes et du nord du pays. La Patagonie est un formidable terrain de jeu, et plus encore un vaste espace d’utopie, hier comme aujourd’hui, pour nombre de voyageurs et rêveurs.Le « charme » est indéniable, il suffit de contempler la nature qui domine ici la culture, et la région n’est pas un paradis pour les photographes par hasard ; quant au caractère « discret », il est également évident, comme en témoignent de nombreux touristes en quête de leur propre expérience “into the wild” et qui s’émerveillent en foulant ces sentiers non battus de la Patagonie. Terre de jeu pour aventuriers, lieu de science pour les chercheurs, espace de refuge pour de riches expatriés, territoire d’expérimentation sinon de rite de passage pour quelques jeunes et sportifs, marcheurs, cyclistes ou flâneurs, la Patagonie chilienne est désormais surtout devenue un enjeu, économique et donc politique, essentiel pour le pays.Cet article, fruit d’un travail en cours, apporte quelques éléments pour tenter de comprendre comment se fabrique et s’établit, dans le temps et dans l’espace, « une destination non touristique » qui, depuis ces dernières années, à la faveur des médias, mais pas seulement, a le vent en poupe. Avec ou sans le consentement des Patagons/Patagoniens ? C’est tout le véritable défi à venir.
The territory of Aysen in southern Chile, officially called "Region XI" has the discreet charm of a forgotten Patagonia. This legendary region has haunted the fertile imagination of explorers and travelers of all kinds. Today, they are so many rich fly fishermen that European or Israeli backpackers, and always more Chileans coming from the middle class and from the north of the country. Patagonia is a wonderful playground, and even more a vast space of utopia, then as now, for many travelers and dreamers.The "charm" is undeniable, simply contemplate the fabulous nature clearly dominating culture here, and the area is not a paradise for photographers by chance. As to the character "discrete", it is also clear, as evidenced by many tourists in search of their own experience "into the wild" and marvel treading the beaten path not of Patagonia. Playground for adventurers, place of science for researchers, refuge area for fortunate expatriates testing ground if not some rite of passage for young athletes, walkers, cyclists or loafers, Chilean Patagonia is now mostly become an issue, and therefore economic policy, rather essential for the country.This article, the first result of a work in progress, brings some elements to try to understand how to manufacture and settled in time and space, "a non-tourist destination", which, in recent years, the for the media but not only has the wind in its sails. With or without the consent of all the habitants of Patagonia? This is the real challenge ahead.
Chili

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.7402
http://journals.openedition.org/etudescaribeennes/7402