Les Pseudholaster (Echinoidea,Holasteroida) du Crétacé de France

In the order of Holasteroida, the fossil record highlights a contradiction between the genus Pseudholaster that appears in the Aptian, whose plastron is prostostern close to the Jurassic ancestors and the genus Holaster, which appears in the Valanginian, whose meridostern plastron appears more derived. This inconsistency can be explained by the ignorance of the plastronal architecture on the part of the early authors. A review of the species of Pseudholaster from the Cretaceous period of France was therefore carried out. The objective was to statistically determine the discriminating morphological characters, and to study the modifications of the architecture of the interambulacrum 5 of the French species belonging to this genus, as well as to the species included in the genus Holaster incorrectly by earlier authors. This review of the species of the genus Pseudholaster begins with a study of the ontogeny of the species Holaster intermedius Münster in Goldfuss, 1826–1833, first representative of the genus Pseudholaster, which appears in the Hauterivian in the Parisian and Rhodano-vocontian basins. The modifications during growth concern the overall shape, but also the plastron architecture: the number of plastron plates increases while the number of plates located between the peristome and the periproct remains fixed. The plastron of this species is protosternal and not meridosternal as Lambert pointed out. The labrum is cupuliform in contact with the second sternal 5a2 by a narrow digitation. However, this arrangement differs from that observed on a protosternal breastplate. This apomorphism of the plastron plate pattern, called “labrotaxienne”, is found in all the Pseudholaster studied, and the study of the architecture of the interambulacrum 5 also reveals a gradual decrease in the number of preanal plates between the oldest (Hauterivian) and the younger (Cenomanian-Lower Turonian) species studied. Most of the French species have been revised, with some synonyms. A new species, P. neraudeaui, is the last known Pseudholaster dated from the upper Cenomanian and lower Turonian of southwestern France. Our study illustrates the evolution of the genus Pseudholaster between the Hauterivian and the early Turonian in France. The interest of the study is to show that the appearance of the genus Pseudholaster is older than that of the genus Holaster. Pseuholaster intermedius, of Hauterivian age, possesses a derived protostern plastron called here “labrotaxien” and not meridostern as defined historically by Lambert, and to reveal that the number of preanals decreases over geological time. This data is essential for future phylogenetic studies. On a palaeobiogeographical level, the study reveals the expansion of the genus Pseudholaster during early Cretaceous in western Europe, with diversification during the Albian, its disappearance during late Cenomanian in the Paris basin while it still persists in the Aquitain basin, its predilection for circalitoral environments.     

Characterization of newly established colorectal cancer cell lines: correlation between cytogenetic abnormalities and allelic deletions associated with multistep tumorigenesis

We have established a series of 20 colorectal cancer cell lines and performed cytogenetic and RFLP analyses to show that the recurrent genetic abnormalities of chromosomes 1, 5, 17 and 18 associated with multistep tumorigenesis in colorectal cancer, and frequently detected as recurrent abnormalities in primary tumours, are also retained in long-term established cell lines. Earlier studies by us and other investigators showed that allelic losses of chromosomes 1 and 17 in primary colorectal cancers predicted poorer survival for the patients (P = 0.03). We utilized the cell lines to identify specific chromosomal sites or gene(s) on chromosomes 1 and 17 which confer more aggressive phenotype. Cytogenetic deletions of chromosome 1p were detected in 14 out of the 20 (70%) cell lines, whereas allelic deletions for 1p using polymorphic markers were detected in 13 out of 18 (72%) informative cell lines for at least one polymorphic marker. We have performed Northern blotting, immunohistochemical staining (p53 mRNA, protein) and RFLP analysis using several probes including p53 and nm23. RFLP analysis using a total of seven polymorphic markers located on 17p and 17q arms showed allelic losses aroundthe p53 locus in 16 out of the 20 cell lines (80%), four of which were losses of thep53 locus itself. In addition, seven cell lines (out of nine informative cases) also showed losses of thenm23 gene, four with concurrent losses of thep53 locus, while the remaining three were homozygous. In addition, five out of seven cell lines withnm23 deletions were derived from hepatic metastatic tumours, and one cell line was obtained from recurrent tumour. A comparison between allelic deletions of 1p and functional loss ofnm23 gene revealed a close association between these two events in cell lines derived from hepatic metastasis. Following immunohistochemical staining, nine out of the twenty cell lines showed high levels (25–80%) of mutant p53, four showed intermediate levels (>20%), and seven had undetectable levels of the protein. Of these seven, four showed complete absence of mRNA. Of the remaining three cell lines one showed aberrant mRNA due to germline rearrangement of thep53 gene, whereas in two cell lines normal levels of mRNA were present. Nineteen of the 20 cell lines had normal germline configurations for thep53 gene, while one showed a rearrangement. These data suggest that functional loss ofp53 andnm23 genes accomplished by a variety of mechanisms may be associated with poor prognosis and survival. In addition, concurrent deletions of chromosome regions 17p, 17q and 1p were closely associated with high-stage hepatic metastatic disease. These cell lines with well-characterized genetic alterations and known clinical history provide an invaluable source of material for various biological and clinical studies relating to multistep colorectal tumorigenesis.     

Influence of genetic architecture on contemporary local evolution in the soapberry bug,Jadera haematoloma: artificial selection on beak length

Little is known about the influence of genetic architecture on local adaptation. We investigated the genetic architecture of the rapid contemporary evolution of mouthparts, the flight polymorphism and life history traits in the soapberry bug Jadera haematoloma (Hemiptera) using laboratory selection. The mouthparts of these seed‐feeding bugs have adapted in 40–50 years by decreasing in length following novel natural selection induced by a host switch to the seeds of an introduced tree with smaller fruits than those of the native host vine. Laboratory selection on beak length in both an ancestral population feeding on the native host and a derived population feeding on the introduced host reveals genetic variance allowing a rapid response (heritabilities of 0.51–0.87) to selection for either longer or shorter beaks. This selection resulted in reverse evolution by restoring long beaks in the derived population and forward evolution by re‐creating short beaks in the ancestral bugs. There were strong genetic correlations (0.68–0.84) in both populations between beak lengths and the frequency of flight morphs, with short beaks associated with short wings. The results reveal a genetically interrelated set of adaptive multivariate traits including both beak length and flight morph. This suite of traits reflects host plant patchiness and seeding phenology. Weaker evidence suggests that egg mass and early egg production may be elements of the same suite. Reversible or forward evolution thus may occur in a broad set of genetically correlated multivariate traits undergoing rapid contemporary adaptation to altered local environments.     

Fractal root system of Melica przewalskyi along different aspect in degraded grassland

Aims Fractal root system is phenotypic plasticity result of plant root architecture to respond to environmental heterogeneity, may reflect the growth strategy of plants to adapt to environmental conditions. Our objective was to explore the relationship between root fractal dimension and fractal abundance of fractal root system of Melica przewalskyi population in response to aspect variation in the northwest of China. Methods The study site was located in a degraded alpine grassland on the northern slope in Qilian Mountains, Gansu Province, China. Survey and sampling were carried out at 40 plots which were set up along four slope aspects transects with 20 m distance between adjacent plots. Handheld GPS was used to determine the elevation, longitude and latitude of each plot. ArcGIS was used to set up digital elevation model (DEM). Community traits were investigated and six individuals roots of M. przewalskyi were collected randomly at each plot. The samples were cleaned and divided into different organs, then scanning the root with the Win-RHIZO for measurements of fractal dimension and fractal abundance in laboratory, and their biomass were then measured after being dried at 80 °C in an oven. Important findings With the slope aspect turned from north to east, west, and south, the density, height and soil moisture content of the plant community displayed a pattern of initial decline, the height, density, root fractal abundance of M. przewalskyi increased and the root fractal dimension decreased. The root fractal dimension was negatively associated with the fractal abundance in all aspects, but the relationship varied along the slope aspects gradient; there was a highly significant negative correlation (p < 0.01) between the root fractal dimension and fractal abundance at north slope and south slope aspect, whereas the correlation only reached a significant level (p < 0.05) at the east slope aspect and west slope aspect; indicating that there is a trade-off between the root fractal dimension and fractal abundance. In addition, when the slope aspect changed from north to east, west and south, the standardized major axis (SMA) slope of the regression equation in the scaling relationships between root fractal dimension and fractal abundance increased (p < 0.05), indicating that the roots of M. przewalskyi at the droughty southern slope have less branch and more sparse in the same soil volume of root exploitation and utilization. Consequently, the resource allocation pattern on reasonable trade-off between root fractal dimension and fractal abundance in different slope aspect of M. przewalskyi, reflects the relationship between the income and the cost of construction of plant root architecture.     

Module-based construction of plasmids for chromosomal integration of the fission yeast Schizosaccharomyces pombe

Integration of an external gene into a fission yeast chromosome is useful to investigate the effect of the gene product. An easy way to knock-in a gene construct is use of an integration plasmid, which can be targeted and inserted to a chromosome through homologous recombination. Despite the advantage of integration, construction of integration plasmids is energy- and time-consuming, because there is no systematic library of integration plasmids with various promoters, fluorescent protein tags, terminators and selection markers; therefore, researchers are often forced to make appropriate ones through multiple rounds of cloning procedures. Here, we establish materials and methods to easily construct integration plasmids. We introduce a convenient cloning system based on Golden Gate DNA shuffling, which enables the connection of multiple DNA fragments at once: any kind of promoters and terminators, the gene of interest, in combination with any fluorescent protein tag genes and any selection markers. Each of those DNA fragments, called a ‘module’, can be tandemly ligated in the order we desire in a single reaction, which yields a circular plasmid in a one-step manner. The resulting plasmids can be integrated through standard methods for transformation. Thus, these materials and methods help easy construction of knock-in strains, and this will further increase the value of fission yeast as a model organism.     

Mitotic drug targets

Mitosis is the key event of the cell cycle during which the sister chromatids are segregated onto two daughter cells. It is well established that abrogation of the normal mitotic progression is a highly efficient concept for anti‐cancer treatment. In fact, various drugs that target microtubules and thus interfere with the function of the mitotic spindle are in clinical use for the treatment of various human malignancies for many years. However, since microtubule inhibitors not only target proliferating cells severe side effects limit their use. Therefore, the identification of novel mitotic drug targets other than microtubules have gained recently much attention. This review will summarize the latest developments on the identification and clinical evaluation of novel mitotic drug targets and will introduce novel concepts for chemotherapy that are based on recent progress in our understanding how mitotic progression is regulated and how anti‐mitotic drugs induce tumor cell death. J. Cell. Biochem. 111: 258–265, 2010. © 2010 Wiley‐Liss, Inc.     

Water use efficiency as a function of leaf age and position within the cotton canopy

The gas exchange properties of whole plant canopies are an integral part of crop productivity and have attracted much attention in recent years. However, insufficient information exists on the coordination of transpiration and CO₂ uptake for individual leaves during the growing season. Single-leaf determinations of net photosynthesis (Pn), transpiration (E) and water use efficiency (WUE) for field-grown cotton (Gossypium hirsutum L.) leaves were recorded during a 2-year field study. Measurements were made at 3 to 4 day intervals on the main-stem and first three sympodial leaves at main-stem node 10 from their unfolding through senescence. Results indicated that all gas exchange parameters changed with individual main-stem and sympodial leaf age. Values of Pn, E and WUE followed a rise and fall pattern with maximum rates achieved at a leaf age of 18 to 20 days. While no significant position effects were observed for Pn, main-stem and sympodial leaves did differ in E and WUE particularly as leaves aged beyond 40 days. For a given leaf age, the main-stem leaf had a significantly lower WUE than the three sympodial leaves. WUE's for the main-stem and three sympodial leaves between the ages of 41 to 50 days were 0.85, 1.30, 1.36 and 1.95 μmol CO₂ mmol⁻¹ H₂O, respectively. The mechanisms which mediated leaf positional differences for WUE were not strictly related to changes in stomatal conductance (g_s·H₂O) since decreases in g_s·H₂O with leaf age were similar for the four leaves. However, significantly different radiant environments with distance along the fruiting branch did indicate the possible involvement of mutual leaf shading in determining WUE. The significance of these findings are presented in relation to light competition within the plant canopy during development.     

Conopy architecture of Larrea tridentata (DC.) Cov., a desert shrub: foliage orientation and direct beam radiation interception

Summary At sites in the United States, creosote bushes (Larrea tridentata (DC.) Cov.) orient foliage clusters predominantly toward the southeast. Foliage of bushes at the southernmost distribution extreme in Mexico shows no predominant orientation. Clusters at all sites are inclined between 33° and 71° from the horizontal. Inclinations are steeper in the drier and hotter Mojave Desert than in the Chihuahuan Desert. Individual leaflets, though not measured, appear more randomly oriented than foliage clusters. In several populations studied, branches were shorter in the southeastern sectors of the crown, reducing self-shading early in the morning. Measurements of direct beam radiation interception by detached branches, using digital image processing, indicated that foliage clusters oriented toward the southeast exhibited less self-shading during spring mornings than clusters oriented northeast. This effect was not apparent at the summer solstice. This type of canopy architecture may tend to minimize self-shading during the morning hours when conditions are more favorable for photosynthesis, resulting in an improved daily water use efficiency.     

Analysis of the biomacromolecular architecture of eukaryotic and prokaryotic serine proteases

Summary We have been developing computational approaches to increase our ability to analyze the growing body of three-dimensional structural data with applications centered on the serine proteases and their natural inhibitors and substrates. It is essential that these approaches emphasize the comparison of these macromolecules at the separate levels of secondary, tertiary and quaternary structure. We assume in our analysis that in functionally related macromolecules (i.e., a family of evolutionarily related enzymes), regions of structural and/or physicochemical similarity will exhibit functional similarity; regions that are different in structure and/or physicochemical properties will function differently and, therefore, be the source of observed specificity. It is the intent of our research to encapsulate such knowledge in a form which is capable of observing patterns which may serve as generalizable rules for macrostructural analysis (Liebman, M.N. 1986. Enzyme 36: 150–163), and to serve as the essential tools for the rational design of modified serine proteases and/or their natural inhibitors by the methods available through genetic engineering.