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A natural population of Drosophila melanogaster was sampled twice over a 5-year interval from the same French locality in the same season. Reaction norms of wing and thorax length and wing/thorax ratio, according to growth temperature (12-31 °C) were analysed in ten isofemale lines for each sample. Reaction norms were very similar between years, showing not only a remarkable stability of the average size but also of the reactivity to temperature. Wing and thorax length reaction norms were characterized by the co-ordinates of their maxima (MV = maximum value of character; TMV = temperature of maximum value). The wing/thorax ratio, which exhibited a decreasing sigmoid norm, was characterized by the co-ordinates of the inflexion point. Again, these characteristic values were found to be very similar for samples between years. The results were further analysed by pooling the 20 lines into a single data set. Heritability was significantly variable according to temperature, but in a fairly irregular way with lowest values at extreme temperatures. Genetic variance of the three traits exhibited more regular variation with a minimum at intermediate temperatures and maxima at extreme high or low temperatures. Such was also the case of evolvability, i.e. the genetic coefficient of variation. Heritability and evolvability were found to be slightly but negatively correlated, showing that they provide independent biological information. The temporal stability of a natural population over the years suggests some stabilizing selection for both mean body size and plasticity. For laboratory evolution experiments, the natural origin population might be useful as a genetic control over time. © Inra/Elsevier, Paris

Plasticite phenotypique de la pigmentation corporelle chez Drosophila: variations correlees entre segments. La plasticite phenotypique de la pigmentation corporelle (trois derniers segments abdominaux et mesothorax) a ete etudiee en fonction de la temperature chez Drosophila melanogaster et Drosophila simulans. Pour chaque espece, deux populations ont ete analysees, provenant de deux localites francaises ayant des conditions climatiques differentes. Pour chaque population, dix lignees isofemelles ont ete elevees a des temperatures comprises entre 14 et 31°C. Deux methodes ont ete utilisees et comparees pour estimer les correlations genetiques (r g ) entre segments, une methode simple utilisant directement les valeurs moyennes des familles (r m ) et une methode theoriquement meilleure, corrigeant les variances et les covariances par la taille de la famille (r c ). Les deux methodes ont produit des donnees similaires mais la premiere (r m ) a ete preferee, car elle permet une estimation dans tous les cas. Les correlations genetiques et phenotypiques diminuent quand on compare des segments plus distants, revelant un gradient autero-posterieur. L'extension de la pigmentation noire est determinee par des systemes genetiques de plus en plus differents dans des segments plus eloignes. Les correlations genetiques sont significativement superieures aux correlations phenotypiques, ce qui est en opposition avec la conjecture de Cheverud, bien que les deux valeurs soient hautement correlees.

Embryonic stem cells (ES cells) are able to differentiate into any cell type, and therefore represent an excellent source for cellular replacement therapies in the case of widespread diseases, for example heart failure, diabetes, Parkinson's disease and spinal cord injury. A major prerequisite for their efficient and safe clinical application is the availability of pure populations for direct cell transplantation or tissue engineering as well as the immunological compatibility of the transplanted cells. The expression of human surface markers under the control of cell type specific promoters represents a promising approach for the selection of cardiomyocytes and other cell types for therapeutic applications. The first human clinical trial using ES cells will start in the United States this year.

La longueur des spermatozoides mesures chez 27 especes de Drosophilides est etudiee au niveau de l'ensemble de la famille (75 especes)