AmSUT1, a sucrose transporter in collection and transport phloem of the putative symplastic phloem loader Alonsoa meridionalis

A sucrose (Suc) transporter cDNA has been cloned from Alonsoa meridionalis, a member of the Scrophulariaceae. This plant species has an open minor vein configuration and translocates mainly raffinose and stachyose in addition to Suc in the phloem (C. Knop, O. Voitsekhovskaja, G. Lohaus [2001] Planta 213: 80-91). These are typical properties of symplastic phloem loaders. For functional characterization, AmSUT1 cDNA was expressed in bakers' yeast (Saccharomyces cerevisiae). Substrate and inhibitor specificities, energy dependence, and Km value of the protein agree well with the properties measured for other Suc transporters of apoplastic phloem loaders. A polyclonal antiserum against the 17 N-terminal amino acids of the A. meridionalis Suc transporter AmSUT1 was used to determine the cellular localization of the AmSUT1 protein. Using fluorescence labeling on sections from A. meridionalis leaves and stems, AmSUT1 was localized exclusively in phloem cells. Further histological characterization identified these cells as companion cells and sieve elements. p-Chloromercuribenzenesulfonic acid affected the sugar exudation of cut leaves in such a way that the exudation rates of Suc and hexoses decreased, whereas those of raffinose and stachyose increased. The data presented indicate that phloem loading of Suc and retrieval of Suc in A. meridionalis are at least partly mediated by the activity of AmSUT1 in addition to symplastic phloem loading.     

Normal immune system development in mice lacking the Deltex-1 RING finger domain

The Notch signaling pathway controls several cell fate decisions during lymphocyte development, from T-cell lineage commitment to the peripheral differentiation of B and T lymphocytes. Deltex-1 is a RING finger ubiquitin ligase which is conserved from Drosophila to humans and has been proposed to be a regulator of Notch signaling. Its pattern of lymphoid expression as well as gain-of-function experiments suggest that Deltex-1 regulates both B-cell lineage and splenic marginal-zone B-cell commitment. Deltex-1 was also found to be highly expressed in germinal-center B cells. To investigate the physiological function of Deltex-1, we generated a mouse strain lacking the Deltex-1 RING finger domain, which is essential for its ubiquitin ligase activity. Deltex-1(Delta/Delta) mice were viable and fertile. A detailed histological analysis did not reveal any defects in major organs. T- and B-cell development was normal, as were humoral responses against T-dependent and T-independent antigens. These data indicate that the Deltex-1 ubiquitin ligase activity is dispensable for mouse development and immune function. Possible compensatory mechanisms, in particular those from a fourth Deltex gene identified during the course of this study, are also discussed.     

Mitochondrial targeting signals and mature peptides of 3-methylcrotonyl-CoA carboxylase

Inherited deficiency of 3-methylcrotonyl-CoA carboxylase (MCC), an enzyme of leucine degradation, is an organic acidemia detectable by expanded newborn screening with a variable phenotype that ranges from asymptomatic to death in infancy. Here, we show that the two subunits of the enzyme (MCCalpha; MCCbeta) are imported into the mitochondrial matrix by the classical pathway involving cleavable amino-terminal targeting presequences. We identified the cleavage sites (Tyr41/Thr42 and Ala22/Tyr23 for MCCalpha and MCCbeta, respectively) of the targeting signals and the amino-termini of the mature polypeptides of MCC and propionyl-CoA carboxylase, a mitochondrial paralog. The amino-termini containing 39 (MCCalpha) or 20 amino acids (MCCbeta) were both necessary and sufficient for targeting. Structural requirements for mitochondrial import were defined by site-directed mutagenesis. Our studies provide the prerequisite to understand the impact of specific mutations on the clinical phenotype of MCC deficiency.     

Bacterial dynamics in spring water of alpine karst aquifers indicates the presence of stable autochthonous microbial endokarst communities

Spring water of two alpine karst aquifers differing in hydrogeology but of nearby catchments were investigated for their bacterial population dynamics. Dolomite karst aquifer spring 1 (DKAS 1) represents a dolomitic-limestone karst aquifer spring showing high average water residence time and relative constant flow. Limestone karst aquifer spring 2 (LKAS 2) constitutes a typical limestone karst aquifer spring with a dynamic hydrological regime and discharge. Dolomite karst aquifer spring 1 yielded constantly lower cell counts and biomasses (median of 15 x 10(6) cells l(-1) and 0.22 microg C l(-1)) as the LKAS 2 (median of 63 x 10(6) cells l(-1) and 1.1 microg C l(-1)) and distribution of morphotypes and mean cell volumes was also different between the considered systems, indicating the influence of hydrogeology on microbial spring water quality. Molecular bacterial V3 16S-rDNA profiles revealed remarkable constancy within each spring water throughout the investigation period. Time course analysis of a flood event in LKAS 2 further supported the trend of the temporal constancy of the microbial community. Except for one case, retrieval of partial and full length 16S rDNA gene sequences from the relative constant DKAS 1 revealed similarities to presently known sequences between 80% to 96%, supporting the discreteness of the microbial populations. The gathered results provide first evidence for the presence of autochthonous microbial endokarst communities (AMEC). Recovery of AMEC may be considered of relevance for the understanding of alpine karst aquifer biogeochemistry and ecology, which is of interest as many alpine and mountainous karst springs are important water resources throughout the world.     

Genetic covariance between indices of body condition and immunocompetence in a passerine bird

Background  

Condition-dependence is a ubiquitous feature of animal life histories and has important implications for both natural and sexual selection. Mate choice, for instance, is typically based on condition-dependent signals. Theory predicts that one reason why condition-dependent signals may be special is that they allow females to scan for genes that confer high parasite resistance. Such explanations require a genetic link between immunocompetence and body condition, but existing evidence is limited to phenotypic associations. It remains unknown, therefore, whether females selecting males with good body condition simply obtain a healthy mate, or if they acquire genes for their offspring that confer high immunocompetence.     

Design and synthesis of a novel, achiral class of highly potent and selective, orally active neurokinin-1 receptor antagonists

The discovery of a novel, achiral pyridine class of potent and orally active neurokinin-1 (NK(1)) receptor antagonists is described. The evaluation of this class is briefly outlined, leading to the identification of netupitant 21 and befetupitant 29, two new proprietary chemical entities with high affinity and excellent CNS penetration.     

Evolution of the vertebrate ParaHox clusters

The ParaHox cluster contains three Hox-related homeobox genes. The evolution of this sister of the Hox-gene clusters has been studied extensively in metazoans with a focus on its early evolution. Its fate within the vertebrate lineage, and in particular following the teleost-specific genome duplication, however, has not received much attention. Three of the four human ParaHox loci are linked with PDGFR family tyrosine kinases. We demonstrate that these loci arose as duplications in an ancestral vertebrate and trace the subsequent history of gene losses. Surprisingly, teleost fishes have not expanded their ParaHox repertoire following the teleost-specific genome duplication, while duplicates of the associated tyrosine kinases have survived, supporting the hypothesis of a large-scale duplication followed by extensive gene loss.     

Fragrep： An Efficient Search Tool for Fragmented Patterns in Genomic Sequences

Many classes of non-coding RNAs （ncRNAs; including Y RNAs, vault RNAs, RNase P RNAs, and MRP RNAs, as well as a novel class recently discovered in Dictyostelium discoideum） can be characterized by a pattern of short but well-conserved sequence elements that are separated by poorly conserved regions of sometimes highly variable lengths. Local alignment algorithms such as BLAST are therefore ill-suited for the discovery of new homologs of such ncRNAs in genomic sequences. The Fragrep tool instead implements an efficient algorithm for detecting the pattern fragments that occur in a given order. For each pattern fragment, the mismatch tolerance and bounds on the length of the intervening sequences can be specified separately. Furthermore, matches can be ranked by a statistically well-motivated scoring scheme.     

Alignments of mitochondrial genome arrangements: applications to metazoan phylogeny

Mitochondrial genomes provide a valuable dataset for phylogenetic studies, in particular of metazoan phylogeny because of the extensive taxon sample that is available. Beyond the traditional sequence-based analysis it is possible to extract phylogenetic information from the gene order. Here we present a novel approach utilizing these data based on cyclic list alignments of the gene orders. A progressive alignment approach is used to combine pairwise list alignments into a multiple alignment of gene orders. Parsimony methods are used to reconstruct phylogenetic trees, ancestral gene orders, and consensus patterns in a straightforward approach. We apply this method to study the phylogeny of protostomes based exclusively on mitochondrial genome arrangements. We, furthermore, demonstrate that our approach is also applicable to the much larger genomes of chloroplasts.