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-Data were analysed from a divergent selection experiment for an indicator of body composition in the mouse, the ratio of gonadal fat pad to body weight (GFPR). Lines were selected for 20 generations for fat (F), lean (L) or were unselected (C), with three replicates of each. Selection was within full-sib families, 16 families per replicate for the first seven generations, eight subsequently. At generation 20, GFPR in the F lines was twice and in the L lines half that of C. A log transformation removed both asymmetry of response and heterogeneity of variance among lines, and so was used throughout. Estimates of genetic variance and heritability (approximately 50%) obtained using REML with an animal model were very similar, whether estimated from the first few generations of selection, or from all 20 generations, or from late generations having fitted pedigree. The estimates were also similar when estimated from selected or control lines. Estimates from REML also agreed with estimates of realised heritability. The results all accord with expectations under the infinitesimal model, despite the four-fold changes in mean. Relaxed selection lines, derived from generation 20, showed little regression in fatness after 40 generations without selection. Les données provenant d'un programme de sélection divergente ontété analysées pour un indicateur de la composition corporelle des souris : la proportion de tissus adipeux gonadal par rapport au poids corporel (GFPR). Trois répliques de chacune des lignées ontété sélectionnées pendant 20 générations pour l'engraissement (F), la minceur (L), ou non sélectionnées. La sélection fut réalisée dans des familles de pleinfrères, 16 familles par réplique durant les sept premières générations et huit pour les suivantes. A la vingtième génération, le GFPR des lignées (F) et (L)étaient respectivement le double et la moitié de celui de (C). Une transformation logarithmique * Correspondence and reprints E-mail: Victor.Martinez@ed.ac.uk 4 V. Martinez et al.permet de supprimer l'asymétrie de la réponse et l'hétérogénéité des variances entre ces deux lignées. Les estimateurs de la variance génétique et de l'héritabilité (approximativement de 50 %) obtenus par le REML avec un modèle animal sont semblablesà ceux obtenus en utilisant les premières générations de sélection, les 20 générations de sélection ou les dernières en employant l'information sur le pedigree jusqu'à la population de base. De plus, en utilisant les lignées sélectionnées et les lignées de contrôle, les estimateurs sont similaires. Les estimations REML sont conformesà celles de l'héritabilité. Tous les résultats sont conformesà ceux attendus sous un modèle infinitésimal malgré une variation de quatre fois la moyenne. Les lignées soumisesà une pression de sélection plus faibleà la vingtième génération, montrent peu de diminution en engraissement après 40 générations sans sélection.sélection / modèle infinitésimal / variance génétique / composition corporelle / souris

The intracellular facultative bacteria Piscirickettsia salmonis is one of the most important pathogens of the Chilean aquaculture. However, there is a lack of information regarding the whole genomic transcriptional response according to different extracellular environments. We used next generation sequencing (NGS) of RNA (RNA-seq) to study the whole transcriptome of an isolate of P. salmonis (FAVET-INBIOGEN) using a cell line culture and a modified cell-free liquid medium, with or without iron supplementation. This was done in order to obtain information about the factors there are involved in virulence and iron acquisition. First, the isolate was grown in the Sf21 cell line; then, the bacteria were cultured into a cell-free liquid medium supplemented or not with iron. We identified in the transcriptome, genes associated with type IV secretion systems, genes related to flagellar structure assembly, several proteases and sigma factors, and genes related to the development of drug resistance. Additionally, we identified for the first time several iron-metabolism associated genes including at least two iron uptake pathways (ferrous iron and ferric iron uptake) that are actually expressed in the different conditions analyzed. We further describe putative genes that are related with the use and storage of iron in the bacteria, which have not been previously described. Several sets of genes related to virulence were expressed in both the cell line and cell-free culture media (for example those related to flagellar structure; such as basal body, MS-ring, C-ring, proximal and distal rod, and filament), which may play roles in other basic processes rather than been restricted to virulence.

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Aim of study: The aim of the study was to assess the effect of water availability on plastic responses and biomass allocation in early growth traits of Pinus radiata D. Don.Area of study: Seedlings of 69 families of P. radiata belonging to five different sites in Central Chile, ranging from coastal range to fothills of the Andes, were grown in controlled conditions to evaluate differences in response to watering.Material and methods: The seedlings were subjected to two watering regimes: well-watered treatment, in which seedlings were watered daily, and water stress treatment in which seedlings were subjected to three cyclic water deficits by watering to container capacity on 12 days cycles each. After twenty-eight weeks root collar diameter, height, shoot dry weight (stem + needles), root dry weight, total dry weight, height/diameter ratio and root/shoot ratio were recorded. Patterns and amounts of phenotypic changes, including changes in biomass allocation, were analyzed.Main results: Families from coastal sites presented high divergence for phenotypic changes, allocating more biomass to shoots, and those families from interior sites presented low phenotypic plasticity, allocating more biomass to roots at the expense of shoots. These changes are interpreted as a plastic response and leads to the conclusion that the local landrace of P. radiata in Chile originating from contrasting environments possess distinct morphological responses to water deficit which in turn leads to phenotypic plasticity.Research highlights: Families belonging to sandy soil sites must be considered for tree breeding in dry areas, selecting those with high root: shoot ratio.Key words: early testing; environmental interaction; ontogeny; plasticity index; water stress.

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