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RNA interference (RNAi) is a useful tool to assess gene function by knocking down expression of a target gene and has been used successfully in domestic and laboratory organisms. However, the use of RNAi for functional genomics has not fully extended into ecological model organisms in natural environments. Assessment of gene function in the wild is important because gene function can be environmentally and context dependent. Here, we present a case study using RNAi to assess gene function in wild paper wasps Polistes metricus, to test roles for two candidate genes ( NADH dehydrogenase ( NADHdh) and retinoid and fatty acid binding protein ( RfaBp)) in the development of reproductive castes. Previous studies have shown that these genes are upregulated in larvae that become queens compared to workers, but this pattern was reversed in the laboratory, making field-based studies necessary. We orally administered dsRNA to larvae in field colonies and found evidence of a short-term knockdown followed by a compensatory rebound in expression for RfaBp. We also observed the predicted worker-like decrease in lipid stores in NADHdh dsRNA treated wasps, suggesting a possible role for NADHdh in caste development. We discuss our results in the context of challenges for using RNAi for functional genomics in ecological model organisms in the field. [ABSTRACT FROM AUTHOR]

Eucalyptus globulus subsp. globulus Labill. (Tasmanian Blue Gum), native to southeast Australia, is a benchmark species for the pulp and paper industry. We genotyped 397 trees from 16 populations of E. globulus representing the native diversity in Australia using 24 microsatellite loci. Eight genetically distinct groups were detected, consistent with genetic groupings detected in previous quantitative and molecular studies. A sample of 29 Portuguese individuals was added to help clarify the origin of the Portuguese landrace. The results suggest a southern and eastern Tasmania origin for the Portuguese landrace. This genetic framework will enable researchers to investigate the provenance of individuals of unknown pedigree and assess the levels of representation of E. globulus natural variation in the Portuguese landrace. [ABSTRACT FROM AUTHOR]

The article presents lists of papers published in the August 2013 and September 2013 issue which include papers on topics such as genome size diversity in sponges, distribution of transposable element the genome of the domestic cow Bos taurus, and genome size diversity patterns in bats.

The article lists the research papers related to genetics, published in the August 2013 and September 2013 issue of the journal.

Transposable elements (TEs) are DNA sequences that possess the ability to move from one genomic location to another. These sequences contribute to a significant fraction of the genomes of most eukaryotes and can impact their architecture and regulation. In this paper, we present the first data related to the identification and characterization of TEs present in the transcriptome of Anticarsia gemmatalis. Approximately, 835 transcripts showed significant similarity to TEs and (or) characteristic domains. Retrotransposons accounted for 71.2% (595 sequences) of the identified elements, while DNA transposons were less abundant, with 240 annotations (28.8%). TEs were classified into 30 superfamilies, with SINE3/5S and Gypsy being the most abundant. Based on the sequences of TEs found in the transcriptome, we were able to locate conserved regions in the chromosomes of this species. The analysis of differential expression of TEs in susceptible and resistant strains, challenged and not challenged with Bacillus thuringiensis (Bt) from in silico analysis, indicated that exposure to Bt can regulate the transcription of mobile genetic elements in the velvetbean caterpillar. Thus, these data contribute significantly to the knowledge of the structure and composition of these elements in the genome of this species, and suggest the role of stress on their expression. [ABSTRACT FROM AUTHOR]

Polygonatum cyrtonema Hua is a traditional Chinese herb medicine, and it is widely distributed in China. The intrageneric taxonomy and phylogenetic relationships within Polygonatum have long been controversial due to their morphological similarity and lacking special DNA barcodes. In this paper, the complete chloroplast genome is a relatively conserved quadripartite structure including a large single copy region of 84 711 bp, a small single copy region of 18 210 bp, and a pair of inverted repeats region of 26 142 bp. A total of 342 simple sequence repeats were identified, and most of them were found to be composed of A/T, including 126 mono-nucleotides and 179 di-nucleotides. Nucleotide diversity was analyzed and eight highly variable regions (psbl∼trnT-CGU, atpF∼atpH, trnT-GGU∼psbD, psaJ∼rps20, trnL-UAG∼ndhD, ndhG∼ndhl, ndhA, and rpl32∼ccsA) were identified as potential molecular markers. Phylogenetic analysis based on the whole chloroplast genome showed that P. cyrtonema, within the family Asparagaceae, is closely related to Polygonatum sibiricum and Polygonatum kingianum. The sequence matK, trnT-GGU & ccsA, and ndhG∼ndhA were identified as three DNA barcodes. The assembly and comparative analysis of P. cyrtonema complete chloroplast genome will provide essential molecular information about the evolution and molecular biology for further study. [ABSTRACT FROM AUTHOR]

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Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the bias (the difference between the expectation (mean) of an estimator and its true value) of genetic distances for small samples. Exact results on this bias have not received much attention in genetic mapping literature. We show that bias drops quickly with increasing sample size for both a backcross population and an F2 in coupling. By contrast, bias may be substantial even for larger sample size for an F2 when markers are in repulsion. It is concluded that Karlin’s map function should be used with care when mapping is done using an F2 population. The same note of caution applies to other map functions such as Haldane’s and Kosambi’s. Finite-sample bias of these latter functions cannot be assessed because of the nonexistence of an expected value, but their median bias is similar to that of Karlin’s function. Ce travail examine le biais (i.e., la différence entre la valeur attendue (moyenne) d’un estimateur et sa vraie valeur) dans la mesure de distances génétiques au moyen de petits effectifs. Des résultats exacts concernant ce biais n’ont pas reçu beaucoup d’attention dans la littérature portant sur la cartographie génétique. Les auteurs montrent que le biais diminue rapidement avec l’accroissement de la taille de l’effectif, tant chez des populations issues d’un rétrocroisement que chez une F2 en couplage. Par contre, ce biais peut être substantiel, même avec de grands effectifs, pour une F2 lorsque les marqueurs sont en répulsion. Les auteurs en concluent qu’il faut être prudent lorsqu’on utilise la fonction de Karlin sur une population F2. La même prudence est de mise lorsqu’on utilise d’autres fonctions comme celles de Haldane ou de Kosambi. Dans ces derniers cas, le biais occasionné par la taille finie de l’effectif ne peut être mesuré en raison de l’absence d’une valeur attendue, mais leur biais médian est semblable à celui obtenu avec la fonction de Karlin. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article announces the winners of the 2020 Genome Publication Awards, including papers on plant genetic resources, the role of epigenetic inheritance on plant evolution, and modular gene regulatory sequence organisation.

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The estimation of recombination frequencies is a crucial step in genetic mapping. For the construction of linkage maps, nonadditive recombination fractions must be transformed into additive map distances. Two of the most commonly used transformations are Kosambi's and Haldane's mapping functions. This paper reports on the calculation of the bias associated with estimation of recombination fractions, Kosambi's distances, and Haldane's distances. I calculated absolute and relative biases numerically for a wide range of recombination fractions and sample sizes. I assumed that the ratio of recombinant gametes to the total number of gametes can be adequately represented by a binomial function. I found that the bias in recombination fraction estimates is negative, i.e., the estimator is an underestimate. However, significant values were only obtained when recombination fractions were large and sample sizes were small. The relevant estimates of recombination fractions were, therefore, nearly unbiased. Haldane's and Kosambi's distances were found to be strongly biased, with positive bias for the most interesting values of recombination fractions and sample sizes. The bias of Kosambi's distance was considerably smaller than the bias of Haldane's distance. L'estimation de la fréquence de recombinaison est une étape cruciale lors de la cartographie génétique. Lors de la construction de cartes génétiques, des fractions non-additives de recombinants sont transformées en distances génétiques additives. Deux des transformations parmi les plus employées sont les fonctions cartographiques de Kosambi et de Haldane. Ce travail porte sur la détermination des biais survenant lors de l'estimation des fractions de recombinants, des distances de Kosambi et des distances de Haldane. L'auteur a calculé les biais numériques absolus et relatifs pour une grande gamme de fractions de recombinants et de tailles d'échantillons. L'auteur a présumé que le ratio de gamètes recombinants versus le nombre total de gamètes était adéquatement représenté par une fonction binomiale. L'auteur a observé que les biais dans l'estimation des fractions de recombinants étaient négatifs, c'est-à-dire que l'estimateur était sous-évalué. Cependant, des valeurs significatives ont été obtenues seulement lorsque les fractions de recombinants étaient grandes et que les échantillons étaient de petite taille. Les estimés des fractions de recombinants sont donc généralement presque sans biais. Les distances de Kosambi et de Haldane présentaient de forts biais, des biais positifs étant observés pour les valeurs les plus intéressantes en matière de fractions de recombinants et de taille des échantillons. Le biais pour la distance de Kosambi était considérablement plus petit que le biais pour la distance de Haldane. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We comment on a recent paper by Rama Singh, who concludes that Mendel deserved to be called the father of genetics, and Darwin would not have understood the significance of Mendel's paper had he read it. We argue that Darwin should have been regarded as the father of genetics not only because he was the first to formulate a unifying theory of heredity, variation, and development - Pangenesis, but also because he clearly described almost all genetical phenomena of fundamental importance, including what he called 'prepotency' and what we now call 'dominance' or 'Mendelian inheritance'. The word 'gene' evolved from Darwin's imagined 'gemmules', instead of Mendel's so-called 'factors'. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Responses to allopolyploidy include unequal expression of duplicated genes, gene silencing, and sometimes genomic rearrangements. In plants, the relationship between allelic expression differences arising from changes in regulatory regions and the resulting phenotype is poorly understood because of the complexity of their genomes and lack of efficient methodology to identify regulatory variation. Identifying functionally important regulatory variation in crops such as hexaploid wheat (Triticum aestivum) is in its infancy. More knowledge is required about the contribution of participatory genomes to its transcriptome. In this paper, we demonstrate the use of allelic imbalance assays to quantify relative expression levels across tissues and growth regimes of homoeologous transcripts of the A, B, and D genomes. Polymorphisms in the type I thionins have been used as an example. We show that expression levels vary markedly and interactively over all factors. For this gene, the B genome is the smallest contributor to the transcriptome and the D genome the largest. As additional sequence information is accumulated across genomes, this assay will allow the simple study of relative expression across multiple homeologous loci. Les changements observés en réponse à l’allopolyploïdie comprennent une expression inégale des gènes dupliqués, l’inactivation génique et, parfois, des réarrangements génomiques, Chez les plantes, les relations entre les différences d’expression allélique en réponse à des changements dans les régions régulatrices et le phénotype qui en résulte sont peu connus en raison de la complexité de leurs génomes et de l’absence de méthode efficace pour identifier la variation dans la régulation. L’identification de la variation dans la régulation qui est importante sur le plan fonctionnel chez des espèces cultivées comme le blé hexaploïde (Triticum aestivum) en est à ses tout premiers débuts. Davantage de connaissances sur la participation des génomes à l’élaboration du transcriptome sont nécessaires. Dans ce travail, les auteurs illustrent l’utilisation d’analyses de déséquilibre allélique pour quantifier les niveaux d’expression relative des transcrits homéologues des génomes A, B et D selon les tissus et les conditions de croissance. Les polymorphismes au sein des thionines de type I sont employés pour les fins de l’exemple. Les auteurs montrent que les niveaux d’expression varient de façon marquée et interactive pour l’ensemble des conditions. Pour ce gène, le génome B est le plus faible contributeur au transcriptome tandis que le génome D est le plus important. Avec l’accumulation d’informations additionnelles sur des séquences chez l’ensemble des génomes, cette analyse permettra d’étudier aisément l’expression relative sur de multiples locus homéologues. [ABSTRACT FROM AUTHOR]

Copyright of Genome is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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The DOPA decarboxylase gene (Ddc) belongs to the “early-late” class of ecdysone-inducible genes in Drosophila melanogaster. Its expression is up-regulated in epidermal tissues by the ecdysone receptor acting through a response element, EcRE. In this paper, we show that another member of the nuclear receptor superfamily, DHR38, may act as a repressor of epidermal Ddc while inducing Ddc expression in neuronal cells. DHR38 does not behave as a classical co-repressor of the ecdysone receptor though, since the site through which DHR38 acts is distinct from the EcRE. Ectopic expression of a Dhr38 cDNA from a heat-shock promoter completely repressed transcription from the endogenous Ddc promoter and from an intact reporter construct in the hypoderm and in imaginal discs. Ectopic DHR38 had no effect on the transcription of a reporter driven by a Ddc fragment missing the DHR38 binding site. Neither reporter expression nor endogenous Ddc transcript levels were affected in a Dhr38 mutant background. Because most mutant organisms pupariate apparently normally and many of these survive to eclose, we believe that some functional redundancy exists within the Dhr38 regulatory network operating in epidermal tissues. In contrast to its apparent repressor function in epidermal tissues, DHR38 may act as a positive regulator of neural Ddc expression. Ectopic expression of DHR38 throughout the CNS induced as much as a 20-fold increase in Ddc transcripts in the set of neurons in which DDC normally appears. Le gène codant pour la décarboxylase DOPA (Ddc) appartient à la classe « tôt-tard » des gènes inductibles par l’ecdysone chez le Drosophila melanogaster. Son expression est accrue dans les tissus épidermiques grâce au récepteur d’ecdysone, lequel agit via un élément cis, EcRE. Dans ce travail, les auteurs montrent qu’un autre membre de la superfamille de récepteurs nucléaires, DHR38, agirait comme répresseur de l’expression épidermique de Ddc, tout en induisant l’expression de Ddc dans les cellules neuronales. DHR38 ne se comporte pas comme un co-répresseur classique du récepteur d’ecdysone puisque le site via lequel agit DHR38 est différent de l’élément EcRE. L’expression ectopique d’un ADNc de Dhr38 à partir d’un promoteur induit par les chocs thermiques a complètement réprimé la transcription du promoteur endogène de Ddc ainsi que d’un gène rapporteur dans l’hypoderme et les disques imaginaux. L’expression ectopique de DHR38 n’a eu aucun effet sur la transcription d’un rapporteur sous le contrôle d’un fragment de Ddc dépourvu du site de liaison de DHR38. Ni l’expression du rapporteur, ni celle de la copie endogène de Ddc n’a été affectée chez un mutant Dhr38. Puisque la plupart des mutants complètent leur pupaison normalement et que plusieurs survivent jusqu’à l’éclosion, les auteurs concluent qu’une redondance fonctionnelle existe au sein de circuit de régulation de Dhr38 dans les tissus épidermiques. Contrairement à son rôle apparent de répresseur dans les tissus épidermiques, DHR38 agirait comme régulateur positif de l’expression neuronale de Ddc. L’expression ectopique de DHR38 dans l’ensemble du CNS induirait une augmentation jusqu’à 20 fois du transcrit Ddc au sein des neurones dans lesquels DDC apparaît normalement. [ABSTRACT FROM AUTHOR]

This paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus. Cet article décrit une étude portant sur les gènes d’ARN ribosomique 5S (ADNr 5S) chez un groupe de 6 espèces appartenant à 4 genres au sein des mugilidés. Chez ces 6 espèces, les répétitions relativement courtes d’ADNr 5S, dont la taille des produits amplifiés par PCR varie entre 219 et 257 pb, présentent une grande homogénéité intragénomique tant au sein des régions codantes qu’au sein des espaceurs (NTS-I). Des reconstructions phylogénétiques sur la base de ces données mettent en relief la plus grande diversité phylogénétique et génétique chez le Mugil cephalus et l’Oedalechilus labeo par rapport aux genres Liza et Chelon. Des analyses comparées de séquences ont révélé une conservation significative des répétitions courtes d’ADNr 5S au sein des genres Chelon et Liza. De plus, une seconde classe d’ADNr 5S, dont la taille variait entre environ 800 et 1100 pb, a été observée chez les échantillons des genres Chelon et Liza. Seules des répétitions courtes ont été trouvées chez le M. cephalus et l’O. labeo. Les séquences de ces longues répétitions d’ADNr 5S, obtenues chez le Chelon labrosus et le Liza ramada, diffèrent en raison de la présence de deux grandes insertions/délétions (indels) dans les espaceurs (NTS-II) et montrent une très grande similarité avec les espaceurs NTS-I. La variation interspécifique de la séquence des espaceurs NTS-II, en dehors des indels, est faible. Les résultats d’hybridations Southern suggèrent la présence au sein d’un même locus chromosomique des répétitions courtes et longues entremêlées. [ABSTRACT FROM AUTHOR]