FGF4 is a limiting factor controlling the proportions of primitive endoderm and epiblast in the ICM of the mouse blastocyst

The primitive endoderm (PE) and epiblast (EPI) are two lineages derived from the inner cell mass (ICM) of the E3.5 blastocyst. Although it has been shown that FGF signaling is necessary and sufficient for PE specification in the ICM, it is unknown what mechanisms control the PE/EPI proportion in the embryo. Because modulation of FGF signaling alone is sufficient to convert all ICM cells to either PE or EPI, a model has been proposed in which the amount of FGF in the embryo controls the PE/EPI proportion. To test this model, we reduced the amount of FGF4, the major FGF in the preimplantation embryo, using various genotypes of Fgf4 mutants. We observed a maternal contribution of Fgf4 in PE specification, but it was dispensable for development. In addition, upon treatment of Fgf4 mutant embryos with exogenous FGF4, we observed a progressive increase of PE proportions in an FGF4 dose dependent manner, regardless of embryo genotype. We conclude that the amount of FGF4 is limited and regulates PE/EPI proportions in the mouse embryo.     

Leaf anatomical studies of Chamaecrista subsect. Baseophyllum (Leguminosae, Caesalpinioideae): new evidence for the up-ranking of the varieties to the species level

This study aims to determine whether morphoanatomical characters of the leaves of the species of Chamaecrista sect. Absus subsection Baseophyllum could be used to support an up-ranking of C. cytisoides varieties to the species level as previously defined by molecular studies. The significance of anatomical adaptive strategies to arid environments is also discussed. Standard light microscopy techniques and histochemical tests were used for both morphoanatomical and histochemical characterization of the leaves. All the species studied share a single-layered epidermis, actinodromous–camptodromous–brochidodromous type of venation, vascular bundles surrounded by layers of fibers bounded externally by a sheath of cells containing solitary crystals, enlarged tracheids at the vein endings, vascular petiole/rachis tissue with a parenchymatous pith, accessory vascular bundles, mucilage idioblasts and hypodermis in the mesophyll, colleters, and non-secretory trichomes. The position and type of stomata, type of mesophyll, number of palisade and spongy parenchyma layers, position of mucilage idioblasts in the mesophyll, and the number of accessory vascular bundles of petiole/rachis provided useful characters for discriminating the eight species of the subsect. Baseophyllum. Histochemical tests reveal the presence of total polysaccharides, pectins, mucilage and phenolic compounds in the idioblasts. Other xeromorphic characters such as thickened outer periclinal cell walls, compact mesophyll, mucilage idioblasts and hypodermis in the mesophyll may help enable the studied species to survive in exposed sunny areas.     

Association of sardine fishery, Sardinella aurita (Teleostei: Clupeidae) and environmental variability of the coastal upwelling ecosystem of Nueva Esparta, Venezuela

The present research is an analysis of Spanish sardine fishing (Sardinella aurita) associated with some climatic and meteorologic parameters of the ecosystem from El Morro Nueva Esparta, Venezuela. The catch and environmental data from the area were taken in the period 1996-2000. Catch data as a function of wind speed, sea surface temperature, air temperature and rain were analyzed by means of simple lineal regression and multiple models. We found a positive correlation of catch with wind speed, and a negative correlation with sea surface temperature, air temperature, and rain. The multiple regression model with intercept had a poor fit, therefore, we made a model without intercept, which improve greatly the fit. A selection of the variables using the forward procedure verified that the independent variables "wind speed" and "air temperature" have a significant relation with catch (p < 0.001) at real time. This method suggests that sea surface temperature and rain have little influence on the catch, and suggests a major availability of resources in the months with low air temperature and the highest wind speed (January-June). Rev.     

Elucidating a history of invasion: population genetics of pirarucu (Arapaima gigas,Actinopterygii, Arapaimidae) in the Madeira River

Hydrobiologia - The spread of non-native fish species is increasing globally and threatening aquatic ecosystems. Identifying the origins, the pathways, and vectors is crucial for managing...     

Isogenic Strains of PHYCOMYCES BLAKESLEEANUS Suitable for Genetic Analysis

The progeny of crosses between wild-type strains of Phycomyces usually do not exhibit all of the expected genotypes from meiosis. By backcrossing, we have isolated a new (+) mating-type strain, A56, which is nearly isogenic with the (-) wild-type NRRL1555 commonly used in Phycomyces research. Tetrad analysis of the backcrosses shows that meiosis becomes more regular as the parental (+) and (-) strains become more isogenic. In our two-factor crosses with unlinked markers, the regularity of meiosis is measured as the percent of reciprocal ditypes plus tetratypes in the progeny. We have shown that this percentage increases from about 15% for crosses between nonisogenic parents to 90% in the eighth backcross. The results indicate that routine, reliable recombination analyses are possible in P. blakesleeanus.     

Complete genome sequence of Corynebacterium pseudotuberculosis strain Cp267, isolated from a llama

In this work we report the genome of Corynebacterium pseudotuberculosis strain 267, isolated from a llama. This pathogen is of great veterinary and economic importance, as it is the cause of caseous lymphadenitis in several livestock species around the world and causes significant losses due to the high cost of treatment.     

Complete Genome Sequence of Corynebacterium pseudotuberculosis Strain 1/06-A, Isolated from a Horse in North America

Corynebacterium pseudotuberculosis causes disease in several animal species, although distinct biovars exist that appear to be restricted to specific hosts. In order to facilitate a better understanding of the differences between biovars, we report here the complete genome sequence of the equine pathogen Corynebacterium pseudotuberculosis strain 1/06-A.     

A gene for carotene cleavage required for pheromone biosynthesis and carotene regulation in the fungus Phycomyces blakesleeanus

Mating and sexual development in fungi are controlled by molecular mechanisms that are specific for each fungal group. Mating in Phycomyces blakesleeanus and other Mucorales requires pheromones derived from β-carotene. Phycomyces mutants in gene carS accumulate large amounts of β-carotene but do not enter the sexual process. We show that carS encodes a β-carotene-cleaving oxygenase that catalyzes the first step in the biosynthesis of a variety of apocarotenoids, including those that act as pheromones. Therefore carS mutants cannot stimulate their sexual partners, although they respond to them. CarS catalyzes the biosynthesis of a β-ring-containing apocarotenoid that inhibits the activity of the carotenogenic enzyme complex in vegetative cells and provides a feedback regulation for the β-carotene pathway. The carS gene product is a keystone in carotenogenesis and in sexual reproduction.     

X-ray crystal structure of the passenger domain of plasmid encoded toxin(Pet), an autotransporter enterotoxin from enteroaggregative Escherichia coli (EAEC)

Autotransporters (ATs) represent a superfamily of proteins produced by a variety of pathogenic bacteria, which include the pathogenic groups of Escherichia coli (E. coli) associated with gastrointestinal and urinary tract infections. We present the first X-ray structure of the passenger domain from the Plasmid-encoded toxin (Pet) a 100 kDa protein at 2.3 Å resolution which is a cause of acute diarrhea in both developing and industrialized countries. Pet is a cytoskeleton-altering toxin that induces loss of actin stress fibers. While Pet (pdb code: 4OM9) shows only a sequence identity of 50% compared to the closest related protein sequence, extracellular serine protease plasmid (EspP) the structural features of both proteins are conserved. A closer structural look reveals that Pet contains a β-pleaded sheet at the sequence region of residues 181–190, the corresponding structural domain in EspP consists of a coiled loop. Secondary, the Pet passenger domain features a more pronounced beta sheet between residues 135 and 143 compared to the structure of EspP.     

Amplification of an alternate transporter gene suppresses the avirulent phenotype of glucose transporter null mutants in Leishmania mexicana

A glucose transporter null mutant of the parasitic protozoan Leishmania mexicana , in which three linked glucose transporter genes have been deleted by targeted gene replacement, is unable to replicate as amastigote forms within phagolysomes of mammalian host macrophages and is avirulent. Spontaneous suppressors of the null mutant have been isolated that partially restore replication of parasites within macrophages. These suppressor mutants have amplified the gene for an alternative hexose transporter, the LmGT4 permease (previously called the D2 permease), on a circular extrachromosomal element, and they overexpress LmGT4 mRNA and protein. The suppressors have also regained the ability to transport hexoses, and they have reverted other phenotypes of the null mutant exhibiting enhanced resistance to oxidative killing, heat shock and starvation for nutrients, as well as augmented levels of the storage carbohydrate β-mannan, increased cell size and increased growth as insect stage promastigotes compared with the unsuppressed mutant. Complementation of the null mutant with the LmGT4 gene on a multicopy episomal expression vector also reverted these phenotypes, confirming that suppression results from amplification of the LmGT4 gene. These results underscore the importance of hexose transporters for the infectious stage of the parasite life cycle.