The SPA1-like proteins SPA3 and SPA4 repress photomorphogenesis in the light

Suppressor of phyA-105 (SPA1) is a phytochrome A-specific signaling intermediate that acts as a light-dependent repressor of photomorphogenesis in Arabidopsis seedlings. SPA1 is part of a small gene family comprising three genes: SPA1-related 2 (SPA2), SPA1-related 3 (SPA3), and SPA1-related 4 (SPA4). Here, we investigate the functions of SPA3 and SPA4, two very closely related genes coding for proteins with 74% identical amino acids. Seedlings with mutations in SPA3 or SPA4 exhibit enhanced photomorphogenesis in the light, but show no phenotype in darkness. While there are small differences between the effects of spa3 and spa4 mutations, it is apparent that SPA3 and SPA4 function to inhibit light responses in continuous far-red, red, and blue light. Phytochrome A is necessary for all aspects of the spa4 mutant phenotype, suggesting that SPA4, like SPA1, acts specifically in phytochrome A signaling. Enhanced photoresponsiveness of spa3 mutants is also fully dependent on phytochrome A in far-red and blue light, but not in red light. Hence, SPA3 function in red light may be dependent on other phytochromes in addition to phytochrome A. Using yeast two-hybrid and in vitro interaction assays, we further show that SPA3 as well as SPA4 can physically interact with the constitutive repressor of light signaling COP1. Deletion analyses suggest that SPA3 and SPA4, like SPA1, bind to the coiled-coil domain of COP1. Taken together, our results have identified two new loci coding for negative regulators that may be involved in fine tuning of light responses by interacting with COP1.     

Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorinating colonies (MK1 and MK2) consisted of rods of different lengths and thicknesses, indicating heterogeneity. Following subcultivation with thiosulfate as alternative electron acceptor and cocultivation with Clostridium celerecrescensT, the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfitobacterium frappieri strain TCP-A was isolated and characterized regarding its taxonomic properties and the spectrum of chlorophenols that it dehalogenated. Four other bacterial strains were coenriched and identified as organisms with closest phylogenetic relatedness to the Clostridium type strains C. indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amplified ribosomal DNA restriction analysis of the original dehalogenating cultures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbial heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectively) was found by dot-blot hybridization, suggesting a relatively low number of the dehalogenating bacterium within the enrichment culture.     

Glucose kinase of Streptomyces coelicolor A3(2): large-scale purification and biochemical analysis

Glucose kinase of Streptomyces coelicolor A3(2) is essential for glucose utilisation and is required for carbon catabolite repression (CCR) exerted through glucose and other carbon sources. The protein belongs to the ROK-family, which comprises bacterial sugar kinases and regulators. To better understand glucose kinase function, we have monitored the cellular activity and demonstrated that the choice of carbon sources did not significantly change the synthesis and activity of the enzyme. The DNA sequence of the Streptomyces lividans glucose kinase gene glkA was determined. The predicted gene product of 317 amino acids was found to be identical to S. coelicolor glucose kinase, suggesting a similar role for this protein in both organisms. A procedure was developed to produce pure histidine-tagged glucose kinase with a yield of approximately 10 mg/l culture. The protein was stable for several weeks and was used to raise polyclonal antibodies. Purified glucose kinase was used to explore protein-protein interaction by surface plasmon resonance. The experiments revealed the existence of a binding activity present in S. coelicolor cell extracts. This indicated that glucose kinase may interact with (an)other factor(s), most likely of protein nature. A possible cross-talk with proteins of the phosphotransferase system, which are involved in carbon catabolite repression in other bacteria, was investigated.     

Comparison of Free-Living Amoebae in Hot Water Systems of Hospitals with Isolates from Moist Sanitary Areas by Identifying Genera and Determining Temperature Tolerance

Legionella-contaminated hot water systems and moist sanitary areas in six hospitals were sampled for amoebae by following a standardized collection protocol. Genus identifications and temperature tolerance determinations were made. Amoebae identified as Hartmannella vermiformis (65%), Echinamoebae spp. (15%), Saccamoebae spp. (12%), and Vahlkampfia spp. (9%) were detected in 29 of 56 (52%) hot water samples. Twenty-three of 49 (47%) swabs obtained from moist areas were amoeba positive. The following genera were identified: Acanthamoeba (22%), Naegleria (22%), Vahlkampfia (20%), Hartmannella (15%), and Vanella (7%). The temperature tolerance of amoebae from hot water systems was strikingly different from that of amoebae from moist areas. At 44°C on agar, 59% of amoebic isolates sampled from hot water systems showed growth. The corresponding value for isolates from moist areas was only 17%. Six Acanthamoeba isolates from the moist areas were considered potential pathogens. Four Hartmannella and two Saccamoeba isolates from hot water could be cultured at 53°C.     

Purification of the Pyruvate Dehydrogenase Multienzyme Complex of Zymomonas mobilis and Identification and Sequence Analysis of the Corresponding Genes

The pyruvate dehydrogenase (PDH) complex of the gram-negative bacterium Zymomonas mobilis was purified to homogeneity. From 250 g of cells, we isolated 1 mg of PDH complex with a specific activity of 12.6 U/mg of protein. Analysis of subunit composition revealed a PDH (E1) consisting of the two subunits E1α (38 kDa) and E1β (56 kDa), a dihydrolipoamide acetyltransferase (E2) of 48 kDa, and a lipoamide dehydrogenase (E3) of 50 kDa. The E2 core of the complex is arranged to form a pentagonal dodecahedron, as shown by electron microscopic images, resembling the quaternary structures of PDH complexes from gram-positive bacteria and eukaryotes. The PDH complex-encoding genes were identified by hybridization experiments and sequence analysis in two separate gene regions in the genome of Z. mobilis. The genes pdhAα (1,065 bp) and pdhAβ (1,389 bp), encoding the E1α and E1β subunits of the E1 component, were located downstream of the gene encoding enolase. The pdhB (1,323 bp) and lpd (1,401 bp) genes, encoding the E2 and E3 components, were identified in an unrelated gene region together with a 450-bp open reading frame (ORF) of unknown function in the order pdhB-ORF2-lpd. Highest similarities of the gene products of the pdhAα, pdhAβ, and pdhB genes were found with the corresponding enzymes of Saccharomyces cerevisiae and other eukaryotes. Like the dihydrolipoamide acetyltransferases of S. cerevisiae and numerous other organisms, the product of the pdhB gene contains a single lipoyl domain. The E1β subunit PDH was found to contain an amino-terminal lipoyl domain, a property which is unique among PDHs.     

Control of spindle orientation in Drosophila by the Par-3-related PDZ-domain protein Bazooka

Background: The orientation of the mitotic spindle influences the asymmetric distribution of cytoplasmic determinants and the positioning of the sibling cell, and therefore has important influences on cell-fate determination and patterning of the embryo. Both the establishment of an axis of polarity and the adjustment of this axis with respect to the coordinates of the embryo have to be controlled. None of the genes identified so far that are involved in these processes seems to have been conserved between flies and nematodes.Results: Here, we show that the bazooka gene encodes a protein with three putative protein-interaction motifs known as PDZ domains and is the first Drosophila representative of the par gene family of Caenorhabditis elegans, members of which are required for establishment of anterior–posterior polarity of the nematode embryo. The bazooka RNA and protein were found to be restricted to the apical cortical cytoplasm of epithelial cells and neuroblasts. Embryos that were mutant for bazooka frequently failed to coordinate the axis of cell polarity with that of the embryo. This was manifested as defective spindle orientation and mispositioning of the daughter cell after division.Conclusions: The Drosophila gene bazooka is likely to be part of a regulatory mechanism required to coordinate the axis of polarity of a cell with that of the embryo. The PDZ domains of Bazooka provide several protein–protein interfaces, which possibly participate in the assembly of a multiprotein complex at the apical pole.     

The Endogenous and Cell Cycle-dependent Phosphorylation of tau Protein in Living Cells: Implications for Alzheimer’s Disease

In Alzheimer’s disease the neuronal microtubule-associated protein tau becomes highly phosphorylated, loses its binding properties, and aggregates into paired helical filaments. There is increasing evidence that the events leading to this hyperphosphorylation are related to mitotic mechanisms. Hence, we have analyzed the physiological phosphorylation of endogenous tau protein in metabolically labeled human neuroblastoma cells and in Chinese hamster ovary cells stably transfected with tau. In nonsynchronized cultures the phosphorylation pattern was remarkably similar in both cell lines, suggesting a similar balance of kinases and phosphatases with respect to tau. Using phosphopeptide mapping and sequencing we identified 17 phosphorylation sites comprising 80–90% of the total phosphate incorporated. Most of these are in SP or TP motifs, except S214 and S262. Since phosphorylation of microtubule-associated proteins increases during mitosis, concomitant with increased microtubule dynamics, we analyzed cells mitotically arrested with nocodazole. This revealed that S214 is a prominent phosphorylation site in metaphase, but not in interphase. Phosphorylation of this residue strongly decreases the tau–microtubule interaction in vitro, suppresses microtubule assembly, and may be a key factor in the observed detachment of tau from microtubules during mitosis. Since S214 is also phosphorylated in Alzheimer’s disease tau, our results support the view that reactivation of the cell cycle machinery is involved in tau hyperphosphorylation.     

The stimulating effect of a cold dark-pretreatment on the etioplast/chloroplast transformation of angiosperms. III. Involvement of the excision factor and of cold-retarded aging processes?

Our question is whether the stimulating effect of a cold dark-pretreatment on the process of de-etiolation in primary leaves of wheat seedlings under subsequent continuous white light is essentially mediated by the retarding effect of highly lowered temperatures on the following processes: aging and/or senescence, realization of the so-called excision factor in detached leaves, decrease of the cytokinin level in detached leaves. The strong stimulating effect of a cold dark-preatreatment remains inspite of progressive aging in parts of the leaves and a strong decrease of the capability of chlorophyll accumulation in detached in contrast to attached leaves. The strong stimulatory effect of a cold dark-pretreatment is not diminished by application of cytokinin or gibberellic acid. The stimulating effect of a cold dark-pretreatment is detectable over several days under continuous light, but it is lost during a warm dark-phase of a few hours duration between the cold dark-pretreatment and the white light phase.     

Liquid chromatography tandem mass spectrometry method for the quantitation of NTBC (2-(nitro-4-trifluoromethylbenzoyl)1,3-cyclohexanedione) in plasma of tyrosinemia type 1 patients

In this study, we describe a bioanalytical method for quantification of NTBC in plasma of patients with hereditary tyrosinemia type 1 (HT-1) using high-performance liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). After protein precipitation with acetonitrile including Mesotrione as internal standard, separation of NTBC was achieved by RP-HPLC. Detection was performed by positive ion electrospray ionization (ESI) in selected reaction monitoring (SRM) mode. NTBC recovery in the developed method was found to be more than 90%. The lower limit of quantification was calculated to be 0.35 μM. The intra-day and inter-day precision of three different quality control samples (measured as RSD%) was less than 10% and 15%, respectively. The standard calibration curves showed good linearity within the range of 2.5–40 μM and the determined correlation coefficients were r² ≥ 0.995. This presented method is rapid, sensitive, specific and suitable for clinical practice and research.