Serratezomines A--C, new alkaloids from Lycopodium serratum var. serratum.
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Alkaloids↗
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Lyconadin A, a novel alkaloid from Lycopodium complanatum.
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Alkaloids↗
A new strategy for cyclopentenone synthesis.
[reaction--see text] A new strategy for the synthesis of 2,3-disubstituted cyclopentenones emerges from two key reactions-the ruthenium-catalyzed three-component coupling of an equivalent of HBr, an alkyne, and a vinyl ketone and the Ni-Cr Barbier type reaction. As a result, these important structures are readily accessed from an alkyne and a vinyl ketone (which derive directly from carboxylic acids). Syntheses of tetrahydrodicranenone B and rosaprostol illustrate the new strategy.
Anti-Infective Agents↗
Rapid alteration of the phosphoproteome in the moss Physcomitrella patens after cytokinin treatment.
Cytokinin hormones are crucial regulators of a large number of processes in plant development. Recently, significant progress has been made toward the elucidation of the molecular details of cytokinin that has led to a model for signal transduction involving a phosphorylation cascade. However, the current knowledge of cytokinin action remains largely unknown and does not explain the different roles of this hormone. To gain further insights into this aspect of cytokinin action and the inducible phosphorelay, we have produced the first large-scale map of a phosphoproteome in the moss Physcomitrella patens. Using a protocol that we recently published (Heintz, D.; et al. Electrophoresis 2004, 25, 1149-1159) that combines IMAC, MALDI-TOF-MS, and LC-MS/MS, a total of 172 phosphopeptide sequences were obtained by a peptide de novo sequencing strategy. Specific P. patens EST and raw genomic databases were interrogated, and protein homology searches resulted in the identification of 112 proteins that were then classified into functional categories. In addition, the temporal dynamics of the phosphoproteome in response to cytokinin stimulation was studied at 2, 4, 6, and 15 min after hormone addition. We identified 13 proteins that were not previously known targets of cytokinin action. Among the responsive proteins, some were involved in metabolism, and several proteins of unknown function were also identified. We have mapped the time course of their activation in response to cytokinin and discussed their hypothetical biological significance. Deciphering these early induced phosphorylation events has shown that the cytokinin effect can be rapid (few minutes), and the duration of this effect can be variable. Also phosphorylation events can be differentially regulated. Taken together our proteomic study provides an enriched look of the multistep phosphorelay system mediating cytokinin response and suggests the existence of a multidirectional interaction between cytokinin and numerous other pathways.
Bryopsida↗
Analysis of the ribosomal RNA gene repeat from the moss Funaria hygrometrica.
Ribosomal DNA from the moss Funaria hygrometrica was obtained by centrifugation of genomic DNA in a Hoechst 33258-CsCl density gradient. One of the three DNA-satellite bands (GC2) represented the ribosomal fraction. After digestion with EcoRI three larger fragments were obtained which hybridized to the large and small ribosomal subunits from Sinapis alba. The fragments were cloned and sequenced. The complete ribosomal DNA consists of 11,132 bp. The analysis of the 18S, 5.8S and 25S rDNA revealed a high sequence and length similarity to other plant sequences. An intron of 169 bp situated 10 bp from the 5' end of the 25 S rDNA was found. The intergenic spacer (IGS) has a length of 5150 bp with 13 highly conserved subrepeats (38 bp except for two of 56 bp) followed directly by 6 other repeated elements of 42-43 bp. Two putative transcription initiation sites (TIS) were identified with some differences to known TIS of angiosperms.
Base Sequence↗
Intergenic sequences of clustered tRNA genes: new type of genetic marker for phylogenetic studies, with application to the taxonomy of liverworts.
We have established a new type of genetic marker in Pellia liverworts that can be used to differentiate between closely related species within this genus. The Pellia intergenic sequences spanning the tandemly repeated nuclear tRNA(Leu) genes were amplified using the PCR technique and, in the case of Pellia neesiana, the tRNA(Leu) tandem region was cloned and sequenced. The length comparison of the intergenic regions allowed for the identification of a number of Pellia species. Additional experiments suggest that this marker can be used to differentiate other species of liverworts and mosses.
Base Sequence↗
The involvement of ubiquitin in vegetative desiccation tolerance.
We have isolated a polyubiquitin cDNA from the modified desiccation-tolerant grass Sporobolus stapfianus. This cDNA, along with a commercially available polyclonal ubiquitin antibody, was used to characterize desiccation/rehydrated-associated changes in ubiquitin-mediated protein degradation in S. stapfianus and the fully desiccation-tolerant moss Tortula ruralis. Northern analysis demonstrated that in S. stapfianus leaves two ubiquitin transcripts, of ca. 1.4 and 1.2 kb, accumulated above control levels during drying and rehydration but were barely detectable in desiccated tissue. The peak in rehydration-associated transcript accumulation coincided with a depletion in ubiquitin monomer levels indicating an increase in protein degradation. Analysis of T. ruralis revealed three ubiquitin transcripts of ca. 1.9, 1.3 and 0.65 kb, with only the 1.3 kb transcript level varying in response to drying and rehydration and all transcripts being stable in dried tissue. Western analysis revealed that conjugated ubiquitin, indicative of proteins targeted for removal, was evident in all samples of Sporobolus but detectable only in slow-drying Tortula which also displayed reduced levels of ubiquitin monomer. These results demonstrate that desiccated T. ruralis gametophyte possesses stable ubiquitin transcripts which can be translated upon rehydration enabling rapid initiation of cellular repair through degradation of certain proteins. This is in contrast to S. stapfianus which requires several hours to replenish depleted ubiquitin transcripts. The ubiquitin response to drying and rehydration in evolutionarily diverse systems is characterized, and the role of repair mechanisms such as ubiquitin-mediated protein degradation in desiccation tolerance is assessed.
Abscisic Acid↗
Structure and functional analysis of the 26S proteasome subunits from plants.
As initial steps to define how the 26S proteasome degrades ubiquitinated proteins in plants, we have characterized many of the subunits that comprise the proteolytic complex from Arabidopsis thaliana. A set of 23 Arabidopsis genes encoding the full complement of core particle (CP) subunits and a collection encoding 12 out of 18 known eukaryotic regulatory particle (RP) subunits, including six AAA-ATPase subunits, were identified. Several of these 26S proteasome genes could complement yeast strains missing the corresponding orthologs. Using this ability of plant subunits to functionally replace yeast counterparts, a parallel structure/function analysis was performed with the RP subunit RPN 10/MCB1, a putative receptor for ubiquitin conjugates. RPN10 is not essential for yeast viability but is required for amino acid analog tolerance and degradation of proteins via the ubiquitin-fusion degradation pathway, a subpathway within the ubiquitin system. Surprisingly, we found that the C-terminal motif required for conjugate recognition by RPN10 is not essential for in vivo functions. Instead, a domain near the N-terminus is required. We have begun to exploit the moss Physcomitrella patens as a model to characterize the plant 26S proteasome using reverse genetics. By homologous recombination, we have successfully disrupted the RPN10 gene. Unlike yeast rpn10delta strains which grow normally, Physcomitrella rpn10delta strains are developmentally arrested, being unable to initiate gametophorogenesis. Further analysis of these mutants revealed that RPN10 is likely required for a developmental program triggered by plant hormones.
Arabidopsis↗
Photoaffinity labelling with the cytokinin agonist azido-CPPU of a 34 kDa peptide of the intracellular pathogenesis-related protein family in the moss Physcomitrella patens.
As in higher plants, the development of the moss Physcomitrella patens is regulated by environmental signals and phytohormones. At the protonema level transition from chloronema to caulonema cells is under auxin control. The formation on second sub-apical caulonema cells of buds that will give rise to the leafy gametophore requires cytokinins. Using [3H]azidoCPPU (1-(2-azido-6-chloropyrid-4-yl)-3-(4-[3H])phenylurea), a photoactivatable cytokinin agonist, we have specifically photolabelled a soluble 34 kDa protein of P. patens. Urea derivatives were very efficient competitors of photolabelling while purine-type cytokinins were poor competitors. The protein UBP34 was purified by affinity chromatography and the sequences of six internal peptides obtained. A cDNA encoding UBP34 was cloned by screening a P. patens protonema cDNA library with a probe amplified by PCR using degenerate primers designed from the peptide sequences. The UBP34 amino acid sequence shows an average sequence identity of 42% with both intracellular PR proteins and the BetV1-related family of plant allergens. Recombinant UBP34 expressed in Escherichia coli was confirmed to bind azidoCPPU.
Amino Acid Sequence↗
Monitoring atmospheric metal pollution: a review of the use of mosses as indicators.
This article reviews the literature on the use of mosses for monitoring atmospheric metal pollution. It discusses the nature of mosses, the mechanisms for moss uptake of metals from the air and wet precipitation, the various forms in which mosses are used for this purpose, and cases in which mosses have been used for monitoring local hot spots of pollution, and regional patterns of metal pollution. Also highlighted are the questions of uptake of metals from the substrates, interspecies differences, and a comparison of the effectiveness of mosses with other indicator materials, among other issues.
Air Pollutants↗
Expansins in the bryophyte Physcomitrella patens.
Expansins are cell wall proteins which play a key function in basic processes of plant growth and differentiation. It has been proposed that expansins are likely to be present in all land plants and, to date, they have been reported in angiosperms, gymnosperms and pteridophytes. In this paper, we provide the first report and analysis of genes encoding expansin-like proteins in the bryophyte, Physcomitrella patens. Our analysis indicates that both alpha- and beta-expansins are present as gene families in this plant and expression analysis indicates that these genes are subject to a complex regulation by both hormonal and environmental factors. In particular, the expression of many expansin genes in P. patens is upregulated by stress conditions, suggesting that they play a role in the specific cellular differentiation displayed by P. patens in response to such stress. Finally, we provide the first report on the generation and analysis of a series of knockout mutants for individual expansin genes.
Abscisic Acid↗
Heavy metal concentration in the moss Pleurozium schreberi in the Niepołomice Forest, Poland: changes during 20 years.
The Niepołomice Forest is a large forest complex (110 km2) situated in southern Poland 10 to 30 km to the east of the urban industrial Kraków agglomeration and steelworks, which was built up on the outskirts of the city in 1950. Due to prevailing westerly winds, the forest is affected by pollutants emitted by both the steelworks and the city. The level of heavy metal contamination in the Niepołomice Forest was described using a sensitive bioindicator - the moss Pleurozium schreberi. Mean concentrations of metals in moss collected in the Niepołomice Forest were Cd - 0.71, Cr - 2.4, Cu - 8.6, Fe - 673, Pb - 12.7, and Zn - 61 mg/kg. Concentrations of heavy metals in moss in the Niepołomice Forest decreased in time. As compared with the relatively clean area in north-eastern Poland (Puszcza Białowieska), the concentration of Fe was 2-9 fold and Pb 4-6 fold higher in the Niepołomice Forest in 1975, while in 1998 4 fold and 2 fold, respectively. In both 1975 and 1998 the most polluted by heavy metals was the western part of the Niepołomice Forest (closest to the pollution sources) and the area along the roads inside the forest complex.
Air Pollutants↗
Thallium in terrestrial environments--occurrence and effects.
In this investigation thallium contents in soil and plants in the EuroRegion Neisse were analysed and the distribution determined. The median top-soil content is 0.5 mg/kg in the area investigated. In this low-contaminated area the moss Pleurozium schreberi contains 0.04-0.13 microg/g and the moss Polytrichumformosum between 0.01 and 0.05 microg/g Tl. The effects of thallium on man and the terrestrial environment were examined. In an epidemiological study a significant positive correlation was found between the thallium content of the two mosses and the incidence of diseases of the circulatory system. The LOEC for thallium in bioassays with terrestrial invertebrates and plants in artificial soil ranged from 1 to 500 mg/kg, which indicates an toxicity of thallium up to 100 times higher than that of Cadmium.
Animals↗
Assessment of the rate of 241Am americium release from the biomass of aquatic plants of the Yenisei River.
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Americium↗
Cyclin D-knockout uncouples developmental progression from sugar availability.
Multicellular organisms need to modulate proliferation and differentiation in response to external conditions. An important role in these processes plays the mitogen-stimulated induction of cyclin D (cycD) gene expression. D-type cyclins have been identified as the crucial intracellular sensors for cell-cycle regulation in all eukaryotes. However, cycD deletions have been found to cause specific phenotypic alterations in animals but not yet in plants. An insertional mutation of a so far uncharacterized Arabidopsis cycD gene did not alter the plant phenotype. To gain new insights into CycD function of land plants, we generated targeted cycD gene knockouts in the moss Physcomitrella patens and observed a surprisingly limited disruption phenotype. While wild-type plants reacted to exogenous glucose sources with prolonged growth of juvenile stages and retarded differentiation, cycD knockouts exhibited developmental progression independent of sugar supply. On the other hand, growth rate, cell sizes or plant size were not affected. Thus, we conclude that Physcomitrella CycD might not be essential for cell-cycle regulation but is important for coupling the developmental progression to nutrient availability.
Blotting, Southern↗
Physcomitrella patens as a model for the study of chloroplast protein transport: conserved machineries between vascular and non-vascular plants.
A single general import pathway in vascular plants mediates the transport of precursor proteins across the two membranes of the chloroplast envelope, and at least four pathways are responsible for thylakoid protein targeting. While the transport systems in the thylakoid are related to bacterial secretion systems, the envelope machinery is thought to have arisen with the endosymbiotic event and to be derived, at least in part, from proteins present in the original endosymbiont. Recently the moss Physcomitrella patens has gained worldwide attention for its ability to undergo homologous recombination in the nuclear genome at rates unseen in any other land plants. Because of this, we were interested to know whether it would be a useful model system for studying chloroplast protein transport. We searched the large database of P. patens expressed sequence tags for chloroplast transport components and found many putative homologues. We obtained full-length sequences for homologues of three Toc components from moss. To our knowledge, this is the first sequence information for these proteins from non-vascular plants. In addition to identifying components of the transport machinery from moss, we isolated plastids and tested their activity in protein import assays. Our data indicate that moss and pea (Pisum sativum) plastid transport systems are functionally similar. These findings identify P. patens as a potentially useful tool for combining genetic and biochemical approaches for the study of chloroplast protein targeting.
Bryopsida↗
Arctic microorganisms respond more to elevated UV-B radiation than CO2.
Surface ultraviolet-B radiation and atmospheric CO2 concentrations have increased as a result of ozone depletion and burning of fossil fuels. The effects are likely to be most apparent in polar regions where ozone holes have developed and ecosystems are particularly sensitive to disturbance. Polar plant communities are dependent on nutrient cycling by soil microorganisms, which represent a significant and highly labile portion of soil carbon (C) and nitrogen (N). It was thought that the soil microbial biomass was unlikely to be affected by exposure of their associated plant communities to increased UV-B. In contrast, increasing atmospheric CO2 concentrations were thought to have a strong effect as a result of greater below-ground C allocation. In addition, there is a growing belief that ozone depletion is of only minor environmental concern because the impacts of UV-B radiation on plant communities are often very subtle. Here we show that 5 years of exposure of a subarctic heath to enhanced UV-B radiation both alone and in combination with elevated CO2 resulted in significant changes in the C:N ratio and in the bacterial community structure of the soil microbial biomass.
Arctic Regions↗
Quantifying nitrogen-fixation in feather moss carpets of boreal forests.
Biological nitrogen (N) fixation is the primary source of N within natural ecosystems, yet the origin of boreal forest N has remained elusive. The boreal forests of Eurasia and North America lack any significant, widespread symbiotic N-fixing plants. With the exception of scattered stands of alder in early primary successional forests, N-fixation in boreal forests is considered to be extremely limited. Nitrogen-fixation in northern European boreal forests has been estimated at only 0.5 kg N ha(-1) yr(-1); however, organic N is accumulated in these ecosystems at a rate of 3 kg N ha(-1) yr(-1) (ref. 8). Our limited understanding of the origin of boreal N is unacceptable given the extent of the boreal forest region, but predictable given our imperfect knowledge of N-fixation. Herein we report on a N-fixing symbiosis between a cyanobacterium (Nostoc sp.) and the ubiquitous feather moss, Pleurozium schreberi (Bird) Mitt. that alone fixes between 1.5 and 2.0 kg N ha(-1) yr(-1) in mid- to late-successional forests of northern Scandinavia and Finland. Previous efforts have probably underestimated N-fixation potential in boreal forests.
Acetylene↗