Diversity, Phylogeny and Expression Patterns of Pou and Six Homeodomain Transcription Factors in Hydrozoan Jellyfish Craspedacusta sowerbyi

Formation of all metazoan bodies is controlled by a group of selector genes including homeobox genes, highly conserved across the entire animal kingdom. The homeobox genes from Pou and Six classes are key members of the regulation cascades determining development of sensory organs, nervous system, gonads and muscles. Besides using common bilaterian models, more attention has recently been targeted at the identification and characterization of these genes within the basal metazoan phyla. Cnidaria as a diploblastic sister group to bilateria with simple and yet specialized organs are suitable models for studies on the sensory organ origin and the associated role of homeobox genes. In this work, Pou and Six homeobox genes, together with a broad range of other sensory-specific transcription factors, were identified in the transcriptome of hydrozoan jellyfish Craspedacusta sowerbyi. Phylogenetic analyses of Pou and Six proteins revealed cnidarian-specific sequence motifs and contributed to the classification of individual factors. The majority of the Craspedacusta sowerbyi Pou and Six homeobox genes are predominantly expressed in statocysts, manubrium and nerve ring, the tissues with sensory and nervous activities. The described diversity and expression patterns of Pou and Six factors in hydrozoan jellyfish highlight their evolutionarily conserved functions. This study extends the knowledge of the cnidarian genome complexity and shows that the transcriptome of hydrozoan jellyfish is generally rich in homeodomain transcription factors employed in the regulation of sensory and nervous functions

Relations entre caractéristiques de retrait et densité du bois chez le pin sylvestre, le sapin pectiné et l'épicéa commun

Des relations entre les caractéristiques de retrait du bois et son infradensité sont recherchées pour le sapin pectiné, l'épicéa commun et le pin sylvestre. Les échantillons utilisés sont des carottes de sondage de 5 mm de diamètre, prélevées sur un ensemble de 928 arbres. Les relations obtenues sont significatives mais restent cependant faibles. Le retrait radial est toujours mieux lié à l'infradensité que le retrait tangentiel. L'introduction d'autres variables telles que la largeur moyenne de cerne, l'âge et la circonférence de l'arbre, n'améliore pas de manière significative les relations mises en évidence.Relationships between wood shrinkage properties and wood density for Scots pine, silver fir and Norway spruce. Relationships between basic wood density, tree circumference, age and wood shrinkage properties were investigated. Increment cores were used from 928 trees; the number of trees sampled for each species is given in table I. The location of the stands in the "Vosges" department is given in figure 1. The shrinkage coefficients, representing the dimensional variation of wood when its moisture content decreases by 1%, were calculated. The compression wood was taken into account as it influences the shrinkage coefficient values (table II). The results of the 3 species were compared (table III): pine wood had the highest values; the values for fir and spruce were identical. The relationship between the different shrinkage coefficients was also investigated (table V). In order to study shrinkage variability, a step-by-step multiple regression was used, with basic density, ring width, age and tree circumference as the parameters. The results are given in table VI and can be summarized as follows: 1) For all species, basic density is the variable which correlates best with all the shrinkage coefficients. Therefore basic density is always the 1st variable in the regression equation; 2) The radial shrinkage coefficient is better correlated with basic density than with volumetric or tangential shrinkage; 3) The other parameters (ring width, age and tree circumference) contribute little to the explanation of shrinkage variability. The correlations between the shrinkage coefficients and basic density are low, especially for fir wood. Figures 3, 4 and 5 show these correlations (each shrinkage coefficient as a function of basic density). All the results are discussed with reference to the literature

La qualité de l'aspect des placages de chênes : mesures de couleur et critères d'appréciation des professionnels français et italiens

L'étude des différentes qualités possibles de l'aspect des placages de chêne (Quercus petraea (Matt) Liebl et Quercus robur L) et des critères qui permettent habituellement aux professionnels de les apprécier a été menée par une enquête (présentation de 53 paires de placage) auprès de 90 professionnels du bois français et italiens, répartis en 71 ateliers ou entreprises. L'objectivité de la démarche a été assurée par le traitement statistique des résultats (analyse factorielle des correspondances et tests du χ2) et par la caractérisation de l'aspect de tous les échantillons présentés par des mesures effectuées dans le système CIELAB de quantification des couleurs. Il ressort des résultats que la différence de couleur (mesurable par ΔE*) entre 2 placages favorise de manière nette la décision de choix. La clarté des placages (mesurable par la luminance L*) est une caractéristique appréciée d'une majorité de professionnels. Le caractère uniforme ou non des placages est également apparu important et bien décrit par la mesure de sL*/mL* (coefficient de variation de la clarté L*). Enfin, la variabilité naturelle des tonalités de couleur (mesurables par l'angle de couleur moyen h*) des placages européens de chêne est largement suffisante pour générer des choix différents, spécifiques de certains groupes professionnels.The quality of appearance of oak veneers: colour measurements and visual appreciation of French and Italian professionals. (Oak logs (Quercus robur L and Quercus petraea (Matt) Liebl) are selected for the wood veneers' industry on the basis of their size, length, circumference, width and regularity of annual rings. After slicing, there are numerous quality indicators used to characterise the appearance of oakwood veneers (colour, figurations of wood, etc). The industrial classification of these different qualities is very complex, normally requiring the evaluation of several criteria. These criteria are descended from empirical and traditional use. The aim of this work was to clearly define these criteria in order to find the best parameters to measure them, using the method of colour measurement CIELAB (1976), developed by the CIE (Commission Internationale de l'Eclairage). For this purpose, an inquiry was carried out, presenting to 90 French and Italian wood professionals a collection of samples of various industrial oak veneers (20 x 22 cm), associated randomly in 53 pairs (fig 1). Each sample had been measured at 20 points using a spectrophotometer (Colorquest Hunterlab), which gives colour values in the CIELAB system. Thus, L* (the lightness), h* (the hue angle) and sL*/mL* (standard deviation for L*, gained from the 20 measures) were obtained. For each pair, an opinion on quality was requested from each professional (preference for sample A, preference for sample B, no preference). It was not revealed to the professionals that the samples had been previously measured for their appearance. Multivariate analysis (Reciprocal Averaging) and χ2 tests, which were used for statistical treatment of data, clearly show that a great difference of colour between 2 veneer samples (measured by the total colour difference ΔE*), is an important factor in the choice of the professionals (fig 2). The first axis of the Reciprocal Averaging (fig 4), is connected with the uniformity of colour of the samples. The second axis shows that natural colour tone variability of European oak veneers is responsible for specific choices depending on different professional groups (fig 4). The standard deviation of the lightness L*, and the hue angle h* appear to be related to these 2 professional criteria which are shown on the first 2 to axis of the analysis (figs 5 and 6). The lightness of oak veneers (closely associated with L*, the lightness) is a very much appreciated characteristic for the majority of professionals (fig 11). In conclusion, it seems that it is possible to obtain some measured parameters which can objectively describe the qualities of the appearance of oak veneers

Modification de couleur du bois de chênes européens exposés à la lumière solaire

L'étude du comportement photochimique du bois d'Abies grandis caractérisé par la quasi-absence de substances extractibles colorées, a permis d'établir un modèle mécanistique capable de rendre compte à l'échelle moléculaire des modifications de couleur du bois exposé à une lumière de type solaire. Ce modèle a été étendu au bois de chênes européens (Quercus robur et petraea), essences riches en substances extractibles colorées et pour lesquelles les caractéristiques de couleur sont un critère de qualité. En plus du jaunissement observé et analysé sur le bois d'Abies grandis, un éclaircissement correspondant à une diminution de l'absorption sur le domaine spectral 500 à 600 nm a été noté. Cette décoloration a pu être imputée, au moins en partie, à la photodégradation des lignines.Wood photodiscoloration of European oak under solar light exposure. A previous study concerning the photochemistry of Abies grandis wood, a species which is characterized by the very low content of colored extractable substances, has made it possible to establish a mechanical model (fig 22) to take into account the discoloration of wood under solar-type light exposure at the molecular level. In this paper, this model was extended to European species of oak (Quercus robur and petraea) with high levels of colored extractable substances and for which the color characteristics are a quality criterion. In addition to the observed and analyzed yellowing in Abies grandis wood, a color lightening corresponding to a lowered absorption over the spectral range (500-600 nm) (figs 2, 6) has been observed. Lignin photodegradation is certainly in part responsible for this decoloration. It has also been shown that oak sapwood and heartwood undergo different kinds of photodecoloration (fig 3). For color photostabilization of oak wood under solar light, the results indicate that it is necessary to use UV absorbers to lower the yellowing due to UV light and antioxidants to inhibit color lightening due to reactions with oxygen

The IICR (inverse instantaneous coalescence rate) as a summary of genomic diversity: insights into demographic inference and model choice

International audienceSeveral inferential methods using genomic data have been proposed to quantify and date population size changes in the history of species. At the same time an increasing number of studies have shown that population structure can generate spurious signals of population size change. Recently, Mazet et al. (2016) introduced, for a sample size of two, a time-dependent parameter, which they called the IICR (inverse instantaneous coalescence rate). The IICR is equivalent to a population size in panmictic models, but not necessarily in structured models. It is characterised by a temporal trajectory that suggests population size changes, as a function of the sampling scheme, even when the total population size was constant. Here, we extend the work of Mazet et al. (2016) by (i) showing how the IICR can be computed for any demographic model of interest, under the coalescent, (ii) applying this approach to models of population structure (1D and 2D stepping stone, split models, two-and three-island asymmetric gene flow, continent-island models), (iii) stressing the importance of the sampling strategy in generating different histories, (iv) arguing that IICR plots can be seen as summaries of genomic information that can thus be used for model choice or model exclusion (v) applying this approach to the question of admixture between humans and Neanderthals. Altogether these results are potentially important given that the widely used PSMC (pairwise sequentially Markovian coalescent) method of Li and Durbin (2011) estimates the IICR of the sample, not necessarily the history of the populations

The IICR and the non-stationary structured coalescent: towards demographic inference with arbitrary changes in population structure

In the last years, a wide range of methods allowing to reconstruct past population size changes from genome-wide data have been developed. At the same time, there has been an increasing recognition that population structure can generate genetic data similar to those produced under models of population size change. Recently, Mazet et al. (Heredity 116:362-371, 2016) showed that, for any model of population structure, it is always possible to find a panmictic model with a particular function of population size changes, having exactly the same distribution of T 2 (the coalescence time for a sample of size two) as that of the structured model. They called this function IICR (Inverse Instantaneous Coalescence Rate) and showed that it does not necessarily correspond to population size changes under non-panmictic models. Besides, most of the methods used to analyse data under models of population structure tend to arbitrarily fix that structure and to minimise or neglect population size changes. Here, we extend the seminal work of Herbots (PhD thesis, University of London, 1994) on the structured coalescent and propose a new framework, the Non-Stationary Structured Coalescent (NSSC) that incorporates demographic events (changes in gene flow and/or deme sizes) to models of nearly any complexity. We show how to compute the IICR under a wide family of stationary and non-stationary models. As an example we address the question of human and Neanderthal evolution and discuss how the NSSC framework allows to interpret genomic data under this new perspective