An empirical demonstration of the ideal free distribution: Little Grebes Tachybaptus ruficollis breeding in intensive agricultural landscapes

The ideal free distribution (IFD) model predicts that a density‐dependent mechanism operates to regulate habitat selection and reproductive performance. We studied a Little Grebe Tachybaptus ruficollis population, which breeds on irrigation ponds in the Vega Baja Valley (southeastern Spain) to test the premises of the IFD model. These ponds are highly dynamic because they are managed according to agricultural requirements, and are subject to different levels of disturbance, which can change the quality of individual ponds across the landscape. Surveys were carried out during the breeding season from 2002 to 2006, with reproduction performance estimated during two consecutive breeding seasons, 2003 and 2004. Occupation frequency differed from random, indicating preference for some ponds over others. Habitat features such as pond construction and design, the presence of submerged vegetation, vegetation along the shore and reed beds, and pond area correlated with occupation frequency and might be considered to be indicators of pond quality. Ponds were occupied sequentially from best to worst. Thus, when the population size increased, the number of low‐quality ponds occupied also increased. High‐quality ponds held more breeding pairs than low‐quality ones, resulting in the mean reproductive success per breeding pair being independent of pond quality. Little Grebes therefore occupy ponds in a manner consistent with the expectations of the IFD model.     

Control of arg gene expression in Salmonella typhimurium by the arginine repressor from Escherichia coli K-12

Summary The regulation of synthesis of arg enzymes in Salmonella typhimurium by the arginine repressor of Escherichia coli K-12 has been reevaluated using a strain of S. typhimurium in which the argR gene was rendered nonfunctional by inserting the translocatable tetracyclineresistance element Tn10 into the argR gene. In contrast to previous studies, the introduction of the argR ⁺ allelle of E. coli on an F-prime factor to the argR::Tn10 S. typhimurium strain reduced the synthesis of arg enzymes to essentially wild-type levels. The elevated levels of arg enzymes observed in other hybrid merodiploids may have been the consequence of the formation of hybrid repressor molecules. The readily scoreable phenotype of tetracycline resistance facilitated establishing linkage of cod and argR (0.6% cotransduction) by P22 phage-mediated transduction.     

The phytochrome gene family in grasses (Poaceae): a phylogeny and evidence that grasses have a subset of the loci found in dicot angiosperms

The phytochrome nuclear gene family encodes photoreceptor proteins that mediate developmental responses to red and far red light throughout the life of the plant. From studies of the dicot flowering plant Arabidopsis, the family has been modeled as comprising five loci, PHYA- PHYE. However, it has been shown recently that the Arabidopsis model may not completely represent some flowering plant groups because additional PHY loci related to PHYA and PHYB of Arabidopsis apparently have evolved independently several times in dicots, and monocot flowering plants may lack orthologs of PHYD and PHYE of Arabidopsis. Nonetheless, the phytochrome nucleotide data were informative in a study of organismal evolution because the loci occur as single copy sequences and appear to be evolving independently. We have continued our investigation of the phytochrome gene family in flowering plants by sampling extensively in the grass family. The phytochrome nuclear DNA data were cladistically analyzed to address the following questions: (1) Are the data consistent with a pattern of differential distribution of phytochrome genes among monocots and higher dicots, with homologs of PHYA, B, C, D, and E present in higher dicots, but of just PHYA, B, and C in monocots, and (2) what phylogenetic pattern within Poaceae do they reveal? Results of these analyses, and of Southern blot experiments, are consistent with the observation that the phytochrome gene family in grasses comprises the same subset of loci detected in other monocots. Furthermore, for studies of organismal phylogeny in the grass family, the data are shown to provide significant support for relationships that are just weakly resolved by other data sets.      

Rapid evolution in a conserved gene family. Evolution of the actin gene family in the sea urchin genus Heliocidaris and related genera

Camarodont sea urchins possess a rapidly evolving actin gene family whose members are expressed in distinct cell lineages in a developmentally regulated fashion. Evolutionary changes in the actin gene family of echinoids include alterations in number of family members, site of expression, and gene linkage, and a dichotomy between rapidly and slowly evolving isoform-specific 3' untranslated regions. We present sequence comparisons and an analysis of the actin gene family in two congeneric sea urchins that develop in radically different modes, Heliocidaris erythrogramma and H. tuberculata. The sequences of several actin genes from the related species Lytechinus variegatus are also presented. We compare the features of the Heliocidaris and Lytechinus actin genes to those of the the actin gene families of other closely related sea urchins and discuss the nature of the evolutionary changes among sea urchin actins and their relationship to developmental mode.      

Deuterostome phylogeny and the sister group of the chordates: evidence from molecules and morphology

Complete coding regions of the 18S rRNA gene of an enteropneust hemichordate and an echinoid and ophiuroid echinoderm were obtained and aligned with 18S rRNA gene sequences of all major chordate clades and four outgroups. Gene sequences were analyzed to test morphological character phylogenies and to assess the strength of the signal. Maximum- parsimony analysis of the sequences fails to support a monophyletic Chordata; the urochordates form the sister taxon to the hemichordates, and together this clade plus the echinoderms forms the sister taxon to the cephalochordates plus craniates. Decay, bootstrap, and tree-length distribution analyses suggest that the signal for inference of dueterostome phylogeny is weak in this molecule. Parsimony analysis of morphological plus molecular characters supports both monophyly of echinoderms plus enteropneust hemichordates and a sister group relationship of this clade to chordates. Evolutionary parsimony does not support chordate monophyly. Neighbor-joining, Fitch-Margoliash, and maximum-likelihood analyses support a chordate lineage that is the sister group to an echinoderm-plus-hemichordate lineage. The results illustrate both the limitations of the 18S rRNA molecule alone for high- level phylogeny inference and the importance of considering both molecular and morphological data in phylogeny reconstruction.      

丙型肝炎病毒NS3/4A丝氨酸蛋白酶瞬时表达小鼠模型的建立

目的:建立丙型肝炎病毒NS3/4A丝氨酸蛋白酶体内活性评价模型。方法:利用NS4A/B是NS3/4A丝氨酸蛋白酶作用底物的特性,构建融合基因NS3/NS4A/B-SEAP,底物片段NS4A/B插在NS3/4A和人分泌性碱性磷酸酶(SEAP)之间,融合基因表达后SEAP的分泌依赖于有活性的NS3/4A在NS4A/B位点的切割。将含融合基因的质粒NS3/4A(△4AB)SEAP通过水动力转染技术转染到小鼠体内,检测小鼠血清中SEAP的活性,高活性的SEAP是该评价体系成立的证据。结果与结论:在瞬时表达NS3/4A的小鼠血清中检测到了高活性的SEAP,建立了可用于评价抗NS3/4A的小鼠体内瞬时模型。     

Molecular cloning and characterization of an alpha1,3 fucosyltransferase, CEFT-1, from Caenorhabditis elegans

We report on the identification, molecular cloning, and characterization of an alpha1,3 fucosyltransferase (alpha1,3FT) expressed by the nematode, Caenorhabditis elegans . Although C. elegans glycoconjugates do not express the Lewis x antigen Galbeta1-- >4[Fucalpha1-->3]GlcNAcbeta-->R, detergent extracts of adult C.elegans contain an alpha1,3FT that can fucosylate both nonsialylated and sialylated acceptor glycans to generate the Lexand sialyl Lexantigens, as well as the lacdiNAc-containing acceptor GalNAcbeta1-->4GlcNAcbeta1-- >R to generate GalNAcbeta1-->4 [Fucalpha1-->3]GlcNAcbeta1-->R. A search of the C.elegans genome database revealed the existence of a gene with 20-23% overall identity to all five cloned human alpha1,3FTs. The putative cDNA for the C.elegans alpha1,3FT (CEFT-1) was amplified by PCR from a cDNA lambdaZAP library, cloned, and sequenced. COS7 cells transiently transfected with cDNA encoding CEFT-1 express the Lex, but not sLexantigen. The CEFT-1 in the transfected cell extracts can synthesize Lex, but not sialyl Lex, using exogenous acceptors. A second fucosyltransferase activity was detected in extracts of C. elegans that transfers Fuc in alpha1,2 linkage to Gal specifically on type-1 chains. The discovery of alpha-fucosyltransferases in C. elegans opens the possibility of using this well-characterized nematode as a model system for studying the role of fucosylated glycans in the development and survival of C.elegans and possibly other helminths.      

Silica-based cationic bilayers as immunoadjuvants

Background  

Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design.