Quantification of Methylated Selenium, Sulfur, and Arsenic in the Environment
Vriens, B. ; Ammann, A.A. ; Hagendorfer, H. ; Lenz, M. ; Berg, M. ; Winkel, L.H.E. - \ 2014
PLoS ONE 9 (2014)7. - ISSN 1932-6203
plasma-mass spectrometry - atomic fluorescence spectrometry - solid-phase microextraction - gas-chromatography - speciation analysis - volatile selenium - natural-waters - icp-ms - elements - air
Biomethylation and volatilization of trace elements may contribute to their redistribution in the environment. However, quantification of volatile, methylated species in the environment is complicated by a lack of straightforward and field-deployable air sampling methods that preserve element speciation. This paper presents a robust and versatile gas trapping method for the simultaneous preconcentration of volatile selenium (Se), sulfur (S), and arsenic (As) species. Using HPLC-HR-ICP-MS and ESI-MS/MS analyses, we demonstrate that volatile Se and S species efficiently transform into specific non-volatile compounds during trapping, which enables the deduction of the original gaseous speciation. With minor adaptations, the presented HPLC-HR-ICP-MS method also allows for the quantification of 13 non-volatile methylated species and oxyanions of Se, S, and As in natural waters. Application of these methods in a peatland indicated that, at the selected sites, fluxes varied between 190–210 ng Se·m-2·d-1, 90–270 ng As·m-2·d-1, and 4–14 µg S·m-2·d-1, and contained at least 70% methylated Se and S species. In the surface water, methylated species were particularly abundant for As (>50% of total As). Our results indicate that methylation plays a significant role in the biogeochemical cycles of these elements
Cloning and characterization of a tuberous root-specific promoter from cassava (Manihot esculenta Crantz)
Koehorst-van Putten, H.J.J. ; Wolters, A.M.A. ; Pereira-Bertram, I.J. ; Berg, H. ; Krol, A.R. van der; Visser, R.G.F. - \ 2012
Planta 236 (2012)6. - ISSN 0032-0935 - p. 1955 - 1965.
bound-starch-synthase - storage roots - transformation - expression - gene - agrobacterium - elements - sequences - database - program
In order to obtain a tuberous root-specific promoter to be used in the transformation of cassava, a 1,728 bp sequence containing the cassava granule-bound starch synthase (GBSSI) promoter was isolated. The sequence proved to contain light- and sugar-responsive cis elements. Part of this sequence (1,167 bp) was cloned into binary vectors to drive expression of the firefly luciferase gene. Cassava cultivar Adira 4 was transformed with this construct or a control construct in which the luciferase gene was cloned behind the 35S promoter. Luciferase activity was measured in leaves, stems, roots and tuberous roots. As expected, the 35S promoter induced luciferase activity in all organs at similar levels, whereas the GBSSI promoter showed very low expression in leaves, stems and roots, but very high expression in tuberous roots. These results show that the cassava GBSSI promoter is an excellent candidate to achieve tuberous root-specific expression in cassava.
Isolation and characterization of strong gene regulatory sequences from apple, Malus x domestica
Schaart, J.G. ; Tinnenbroek, I.E.M. ; Krens, F.A. - \ 2011
Tree Genetics and Genomes 7 (2011)1. - ISSN 1614-2942 - p. 135 - 142.
rbcs-3a gene - expression - plants - elements - agrobacterium - arabidopsis - cisgenesis - resistance - promoters - tissues
For the strong expression of genes in plant tissue, the availability of specific gene regulatory sequences is desired. We cloned promoter and terminator sequences of an apple (Malus x domestica) ribulose biphosphate carboxylase small subunit gene (MdRbcS), which is known for its high expression and used gus reporter gene expression to test the regulatory activity of the isolated promoter and terminator sequences in transgenic tobacco. The MdRbcS promoter itself seemed to be less strong than the CaMV35S promoter when both used in combination with the nos terminator. However, the combination of the promoter and terminator of MdRbcS was able to drive gus to similar expression levels as the reference construct with CaMV35S promoter and nos terminator. This observation indicates the importance of the terminator sequence for gene expression. It is concluded that the combination of the MdRbcS promoter and terminator is a suitable regulatory sequence set for the expression of transgenes to a high level in plants and for intragenesis in apple specifically
Genome sequence and analysis of the tuber crop potato
Xu, X. ; Pan, S.K. ; Cheng, S.F. ; Zhang, B. ; Bachem, C.W.B. ; Boer, J.M. de; Borm, T.J.A. ; Kloosterman, B.A. ; Eck, H.J. van; Datema, E. ; Goverse, A. ; Ham, R.C.H.J. van; Visser, R.G.F. - \ 2011
Nature 475 (2011). - ISSN 0028-0836 - p. 189 - 195.
eukaryotic genomes - resistance genes - in-vitro - rna-seq - solanum - tool - identification - elements - reveals - maize
Potato (Solanum tuberosum L.) is the world’s most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop
Serial and Parallel Processes in Working Memory after Practice
Oberauer, K. ; Bialkova, S.E. - \ 2011
Journal of Experimental Psychology: Human Perception and Performance 37 (2011)2. - ISSN 0096-1523 - p. 606 - 614.
dual-task performance - attention - focus - elements
Six young adults practiced for 36 sessions on a working-memory updating task in which 2 digits and 2 spatial positions were continuously updated. Participants either did 1 updating operation at a time, or attempted 1 numerical and 1 spatial operation at the same time. In contrast to previous research using the same paradigm with a single digit and a single dot, dual-task costs were not eliminated with practice. Costs of switching between digits and between spatial positions were found throughout practice, supporting the existence of a focus of attention in working memory that can hold 1 digit and 1 spatial position simultaneously, but is not expanded to hold 2 elements of the same kind. The results can be understood by assuming that observed limits on parallel processing, as well as on the capacity of the focus of attention, arise not from structural constraints but rather reflect the optimal configuration of the cognitive system for avoiding information cross-talk in a given task.
What determines consumer attention to nutrition labels?
Bialkova, S.E. ; Trijp, J.C.M. van - \ 2010
Food Quality and Preference 21 (2010)8. - ISSN 0950-3293 - p. 1042 - 1051.
visual-search - working-memory - pop-out - information - displays - identification - perception - selection - elements - targets
To identify the key determinants of consumer attention to nutrition labels, visual search tasks (present – absent; one – two targets) were used as an effective experimental tool. The main manipulation concerned: set size (number of labels on front of pack); label characteristics (display size, position of the label on frontof-pack, colour scheme); and familiarity with type of the label and its location on the front of pack. Attention capture was faster and more accurate when the label was present rather than absent, with doubled rather than standard display size, and with mono- rather than polychromatic colouring. There was performance benefit when the type of label and its location on the package did not change in two consecutive exposures, suggesting that nutrition logos should be printed in a consistent location on the package. The results confirm our hypotheses that display size, colour scheme, familiarity with the label and its location on the front of the pack are key determinants of consumer attention to labels. These findings are crucial to better understanding consumer attention to labels and thus the impact of nutrition information on healthy food choice.
Genetic and nongenetic variation in concentration of selenium, calcium, potassium, zinc, magnesium, and phosphorus in milk of Dutch Holstein-Friesian cows
Hulzen, K.J.E. van; Sprong, R.C. ; Meer, R. van der; Arendonk, J.A.M. van - \ 2009
Journal of Dairy Science 92 (2009)11. - ISSN 0022-0302 - p. 5754 - 5759.
production traits - dairy-cows - parameters - cheese - plasma - supplementation - transport - proteins - minerals - elements
Minerals found in milk, such as Se, Ca, K, Zn, Mg, and P, contribute to several vital physiological processes. The aim of this study was to quantify the genetic variation in levels of Se, Ca, K, Zn, Mg, and P in milk and to quantify the between-herd variation in the levels of these minerals in milk. One morning milk sample from each of 1,860 Dutch Holstein-Friesian cows from 388 commercial herds in the Netherlands was used. Concentration of minerals was determined by inductively coupled plasma-atomic emission spectrometry. Variance components were estimated using an animal model with covariates for days in milk and age at first calving; fixed effects for season of calving and effect of test or proven bull; and random effects for animal, herd, and error. Heritability and proportion of phenotypic variation that can be explained by herd were estimated using univariate analysis. The intraherd heritability for Se was low (0.20) whereas herd explained 65% of the total variation in Se. Variation between herds most likely results from variation in Se content in the feed, which partly reflects variation in Se levels in the soil. Intraherd heritabilities for Ca, K, Zn, Mg, and P were moderate to high and were 0.57, 0.46, 0.41, 0.60, and 0.62, respectively. For Ca, K, Zn, Mg, and P, the proportions of phenotypic variation that could be explained by herd were low (0.13–0.24). This study shows that there are possibilities for altering the mineral composition of milk. For Ca, K, Zn, Mg, and P, there are good prospects for selective breeding whereas, for Se, measures at farm level may be more effective
Comparative AFLP reveals paternal sex ratio chromosome specific DNA sequences in the parasitoid wasp Trichogramma kaykai
Vugt, J.J.F.A. van; Hulst, R.G.M. van der; Pruijssers, A. ; Verbaarschot, P.G.H. ; Stouthamer, R. ; Jong, H. de - \ 2009
Genome 52 (2009)5. - ISSN 0831-2796 - p. 447 - 455.
selfish b-chromosome - rye secale-cereale - nasonia-vitripennis - molecular characterization - crepis-capillaris - bombyx-mori - psr - retrotransposon - transmission - elements
The parasitoid wasp Trichogramma kaykai with a haplo-diploid sex determination has a B chromosome called the paternal sex ratio (PSR) chromosome that confers paternal genome loss during early embryogenesis, resulting in male offspring. So far, it is not well known whether the PSR chromosome has unique DNA sequence characteristics. By comparative AFLP fingerprinting of genomic DNA from wasps with and without the PSR chromosome, we isolated DNA from PSR-specific bands. Fourteen of such DNA fragments were analysed to confirm their PSR specificity. Seven were sequenced and two (PT-AFLP 1 and PT-AFLP1 3) were identified as parts of retrotransposon genes based on BLAST searches. Internal primers designed from a third AFLP fragment allowed PCR amplification of a PSR chromosome specific marker, which can be used to screen for the PSR trait in male wasps. Southern analysis revealed a dispersed repetitive nature of this third sequence in the T. kaykai genome, suggesting that it is part of a transposon. A fourth AFLP fragment (PT-AFLP 5) appears to be a large repetitive sequence on the PSR chromosome. This sequence is also found in the genome of both T. kaykai and the closely related species Trichogramma deion, but its distribution on the PSR chromosome strongly resembles that of T. deion rather than that of T. kaykai. Our results provide further insight into the repetitive nature of sequences comprising B chromosomes and their similarities with their host and closely related species
The effect of naturally acidified irrigation water on agricultural volcanic soils. The case of Asembagus, Java, Indonesia
Los, A.M.D. ; Vriend, S.P. ; Bergen, M.J. ; Gaans, R.F.M. - \ 2008
Journal of Geochemical Exploration 96 (2008)1. - ISSN 0375-6742 - p. 53 - 68.
mine tailings - forest soils - acidification - netherlands - deposition - aluminum - elements - sulfate - river - iron
Acid water from the Banyuputih river (pH similar to 3.5) is used for the irrigation of agricultural land in the Asembagus coastal area (East Java, Indonesia), with harmful consequences for rice yields. The river water has an unusual composition which is caused by seepage from the acidic Kawah Ijen crater lake into the river. This unique irrigation setting allows the study of soil acidification in situ. This paper assesses the effects of volcanogenically contaminated irrigation water on the chemical properties of the agricultural soils. The changes in soil properties were evaluated by comparing samples taken from the topsoil and sub-soil (1-3 m depth) from areas irrigated with acid water and areas irrigated with neutral water. The field survey thus resulted in four soil categories. Bulk soil composition, organic matter content, moisture content and particle size distribution were determined. Reactive phases were quantified with the selective extractions 1 M KCl, 0.1 M Na-pyrophosphate and 0.2 M acid ammonium oxalate (AAO). By comparing the four soil categories it is shown that the use of the naturally polluted irrigation water has had a large influence on the chemical composition of the topsoil. The composition of the soil solution has changed over the entire investigated soil profile. Furthermore the acid irrigation water has strongly modified the composition of the reactive phases, extracted as KCl, pyrophosphate, and AAO extractable elements, and also the bulk soil composition has been significantly modified. Overall this has resulted in the net dissolution of some elements and the net precipitation of others. The changes in the reactive phases and bulk soil composition are only apparent in the topsoil (0-20 cm) but not in the deeper soil.
Small CRISPR RNAs guide antiviral defense in prokaryotes
Brouns, S.J.J. ; Jore, M.M. ; Lundgren, M. ; Westra, E.R. ; Slijkhuis, R.J. ; Snijders, A.P. ; Dickman, M.J. ; Makarova, K.S. ; Koonin, E.V. ; Oost, J. van der - \ 2008
Science 321 (2008)5891. - ISSN 0036-8075 - p. 960 - 964.
provides acquired-resistance - streptococcus-thermophilus - repeats - identification - elements - dna - evolutionary - sequence - viruses - system
Prokaryotes acquire virus resistance by integrating short fragments of viral nucleic acid into clusters of regularly interspaced short palindromic repeats (CRISPRs). Here we show how virus-derived sequences contained in CRISPRs are used by CRISPR-associated (Cas) proteins from the host to mediate an antiviral response that counteracts infection. After transcription of the CRISPR, a complex of Cas proteins termed Cascade cleaves a CRISPR RNA precursor in each repeat and retains the cleavage products containing the virus-derived sequence. Assisted by the helicase Cas3, these mature CRISPR RNAs then serve as small guide RNAs that enable Cascade to interfere with virus proliferation. Our results demonstrate that the formation of mature guide RNAs by the CRISPR RNA endonuclease subunit of Cascade is a mechanistic requirement for antiviral defense
Dust storm erosion and its impact on soil carbon and nitrogen losses in Northern China
Wang Xiaobin, ; Oenema, O. ; Hoogmoed, W.B. ; Perdok, U.D. ; Cai, D. - \ 2006
Catena 66 (2006)3. - ISSN 0341-8162 - p. 221 - 227.
loess plateau - wind erosion - deposition - elements - land
There is increased awareness of the environmental impacts of soil carbon (C) and nitrogen (N) losses through wind erosion, especially in areas heavily affected by dust storm erosion. This paper reviews the recent literature concerning dust storm-related soil erosion and its impact on soil C and N losses in northern China. The purpose of our study is to provide an overview of the area of erosion-affected soils and to estimate the magnitude of soil C and N losses from farmland affected by dust storm erosion. According to the second national soil erosion remote-sensing survey in 2000, the area affected by wind erosion was 1.91 million km2, accounting for 20% of the total land area in China. This area is expanding quickly as the incidence of heavy dust storms has greatly increased over the last five decades, mainly as a result of the intensification of soil cultivation. The economic and ecological damage caused by wind erosion is considerable. Heavily affected areas show a loss of nutrients and organic carbon in soils and the heavily degraded soils are much less productive. Compared with the non-degraded soil, the C and N contents in degraded soils have declined by 66% and 73%, respectively. The estimated annual losses per cm toplayer of soil C and N by dust storm erosion in northern China range from 53 to 1044 kg ha¿ 1 and 5 to 90 kg ha¿ 1, respectively. Field studies suggest that soil losses by wind erosion can be reduced by up to 79% when farmers shift from conventional soil tillage methods to no-till. Thus shifting to no-till or reduced tillage systems is an effective practice for protecting soil and soil nutrients. Our study indicates that soil conservation measures along with improved soil fertility management measures should be promoted in dry-land farming areas of northern China. As erosion is a major mechanism of nutrient withdrawal in these areas, we plead for the development of accurate methods for its assessment and for the incorporation of erosion, as a nutrient output term, in nutrient budget studies.
Dynamics of dsRNA mycoviruses in black Aspergillus population.
Diepeningen, A.D. van; Debets, A.J.M. ; Hoekstra, R.F. - \ 2006
Fungal Genetics and Biology 43 (2006)6. - ISSN 1087-1845 - p. 446 - 452.
double-stranded-rna - fragment-length-polymorphisms - chestnut blight fungus - niger aggregate - virus transfer - dna - cryphonectria - transmission - nidulans - elements
Approximately 10% of all examined 668 representatives of black Aspergillus species, independent of worldwide location, were infected with double-stranded RNA (dsRNA) mycoviruses. These isometric viruses (25-40 nm diameter) contained a variety of often multiple segments of different dsRNA sizes ranging from 0.8 to 4.4 kb in size. In one strain the virus shows clear visible effects on its host with non-sporulating sectors. We quantified the fitness costs of these and more 'cryptic' virus infections on mycelial growth rate and spore production, and on competitive ability with respect to other strains under different growth conditions. Mycovirus infection proved detrimental in all these measures. The reduced success in interference competition due to mycovirus infection belies co-evolution of mycovirus and host to a mutually beneficial symbiosis, like in killer virus systems in yeast and smut and agrees more to recent infections. For a stable virus infection frequency in the black Aspergillus population, fitness costs and spontaneous loss should be balanced with new infections. Implications of even small viral fitness effects combined with the observed transmission limits for host and mycovirus are discussed
Temporal variation of trace metal geochemistry in floodplain lake sediment subject to dynamic hydrological conditions
Griethuysen, C. van; Luitwieler, M. ; Joziasse, J. ; Koelmans, A.A. - \ 2005
Environmental Pollution 137 (2005)2. - ISSN 0269-7491 - p. 281 - 294.
zware metalen - geochemie - meren - oppervlaktewater - waterverontreiniging - stroomvlakten - hydrologie - nederland - gelderland - land van maas en waal - heavy metals - geochemistry - lakes - surface water - water pollution - floodplains - hydrology - netherlands - gelderland - land van maas en waal - acid-volatile sulfide - fresh-water sediments - elements - estuary - solids - avs
Climate change and land use may significantly influence metal cycling in dynamic river systems. We studied temporal variation of sediment characteristics in a floodplain lake, including concentrations of dissolved organic carbon, acid volatile sulfide and trace metals. The sampling period included a severe winter inundation and a dramatic water level drop during summer. Temporal changes were interpreted using multivariate analysis and chemical equilibrium calculations. Metal concentrations in sediment increased with depth, indicating a gradual improvement of sediment quality. In contrast, dissolved metal concentrations were highest in top layers due to mobilization from oxyhydroxides and precipitation with sulfides in deeper layers. Inundation had a mobilizing effect as it stimulated resuspension and oxygenation of sediment top layers. Water table lowering combined with organic matter decomposition led to immobilization due to sulfide formation. The chemistry of the sediments was consistent with model calculations, especially for macro-elements. The results illustrate the importance of seasonality for metal risk assessment.
A comparison of the digestibility of a range of lupin and soybean protein products when fed to either Atlantic salmon (Salmo salar) or rainbow trout (Oncorhynchus mykiss)
Glencross, B.D. ; Carter, C.G. ; Duijster, N. ; Evans, D.R. ; Dods, K. ; McCafferty, P. ; Hawkins, W.E. ; Maas, R. van der; Sipsas, S. - \ 2004
Aquaculture 237 (2004)39539. - ISSN 0044-8486 - p. 333 - 346.
fish-meal - feed ingredients - kernel meals - fed diets - replacement - growth - oligosaccharides - angustifolius - elements - energy
This study compares the digestibility of a series of lupin and soybean protein products when fed to either rainbow trout or Atlantic salmon. The test ingredients in the study, from one of two key grain resources (lupins: Lupinus angustifolius and soybeans), represented various levels of processing of each grain in order to increase the protein content of the meals. A reference ingredient of enzymatically hydrolyzed casein (EHC) was also included in the study. The rainbow trout (266±18 g) were housed in freshwater tanks (250 l, salinity
An ITS phylogeny of Leccinum and an analysis of the evolution of minisatellite-like sequences within ITS1
Bakker, H.C. den; Gravendeel, B. ; Kuyper, T.W. - \ 2004
Mycologia 96 (2004)1. - ISSN 0027-5514 - p. 102 - 118.
internal transcribed spacer - rna secondary structure - tandem repeat - dna-sequences - fungi - elements - program - gene
Phylogenetic relationships of the European species of Leccinum (Boletales, Boletaceae) were investigated by maximum parsimony, Bayesian and likelihood analyses of nrITS1-5.8S-ITS2 and 28S sequences. The separate gene trees inferred were largely concordant, and their combined analysis indicates that several traditional sectional and species-level taxonomic schemes are artificial. In Leccinum, the nrITS region ranges in size from 694 to 1480 bp. This extreme length heterogeneity is localized to a part of the ITS1 spacer that contains a minisatellite characterized by the repeated presence of CTATTGAAAAG and CTAATAGAAAG core sequences and mutational derivatives thereof. The number of core sequences present in the minisatellite varied from 12 to 36. Intra-individual sequence variation of the minisatellite was always smaller than between different species, indicating that concerted evolution proceeds rapidly enough to retain phylogenetic signal at the infraspecific level. In contrast, the evolutionary pattern exhibited by the major ITS1 repeat types found was homoplastic when mapped onto the species lineages inferred from the combined 5.8S-ITS2 sequences. The minisatellite therefore appears not to be useful for phylogeny reconstruction at or above the species level.
Toxicity of simple mixtures to the nematode Caenhorhabditis elegans in relation to soil sorption
Jonker, M.J. ; Sweijen, R.A.J.C. ; Kammenga, J.E. - \ 2004
Environmental Toxicology and Chemistry 23 (2004)2. - ISSN 0730-7268 - p. 480 - 488.
copper - zinc - pesticides - adsorption - elements - cadmium - models - metals - lc50 - lead
Single and combined toxicity of copper-zinc, copper-cadmium, cadmium-lead, copper-carbendazim, and copper-carbendazimiprodione to the nematode Caenorhabditis elegans in soil was studied. The one-week population increase was estimated as the toxicity endpoint. The aim was to study the relationship between mixture interactions in the soil and the combined toxic effect. Soil sorption was quantified using the Freundlich adsorption constant. Joint toxicity patterns were quantified by comparing mixture effects to the effect of individual constituents and were related to total metal concentrations in the soil, water-soluble concentrations, and 0.01 M CaCl2-extractable concentrations. The metal with the highest adsorption constant influenced the sorption of metal with the lowest adsorption constant when both were combined, indicating interaction. Consequently, both the composition of the mixture as well as the relative toxicity of individual mixture constituents differed between total, water-soluble, and CaCl2-extractable concentrations, which was taken into account in the data quantification procedure that was applied. Both the additive and the independent model were generally inadequate to describe the effects of metal mixtures. Compared to the additive model, synergism was observed at dose levels higher than the median effect isobole. A general relationship between mixture interactions in the soil and the combined toxicity was not found.
Meetnet kleine landschapselementen; studie naar methodiek, haalbaarheid en kosten aan de hand van proefinventarisaties
Oosterbaan, A. ; Berg, C.A. van den; Blitterswijk, H. van; Griffioen, A.J. ; Frissel, J.Y. ; Baas, H.G. ; Pels, M.S. - \ 2004
Wageningen : Alterra (Alterra rapport 897) - 54
landschap - elementen - classificatie - monitoring - inventarisaties - methodologie - haalbaarheidsstudies - landscape - elements - classification - monitoring - inventories - methodology - feasibility studies
Zowel bij het Rijk, de Provincies, Gemeenten als planners en beheerders bestaat grote behoefte aan informatie over kleine landschapselementen. Als voorstudie voor een landelijk meetnet zijn in 3 gebieden proefinventarisaties uitgevoerd van kleine landschapselementen. De ontwikkelde, maar nog wel te optimaliseren, methodiek voor inventarisatie (met hulp van vrijwilligers) en digitale opslag en verwerking blijkt goed te werken en betaalbaar.
What drives plant stress genes?
Aarts, M.G.M. ; Fiers, M.W.E.J. - \ 2003
Trends in Plant Science 8 (2003)3. - ISSN 1360-1385 - p. 99 - 102.
saccharomyces-cerevisiae - transcription factors - promoter - arabidopsis - expression - elements - binding - identification - aerenchyma - responses
Currently, there is a lot of interest in the plant stress response. Using large-scale genomics approaches, more and more genes are being identified that are involved in or even regulate this complex process. The recent boost in expression profile analyses for several plant stress responses has enabled the identification of new promoter elements as important factors in establishing the expression regulatory network controlling plant stress response.
Sexual transmission of the [Het-s] prion leads to meiotic drive in Podospora anserina
Dalstra, H.J.P. ; Swart, K. ; Debets, A.J.M. ; Saupe, S.J. ; Hoekstra, R.F. - \ 2003
Proceedings of the National Academy of Sciences of the United States of America 100 (2003). - ISSN 0027-8424 - p. 6616 - 6621.
fungus podospora-anserina - heterokaryon incompatibility - spore killer - filamentous fungi - neurospora - protein - elements - products - meiosis - analog
In the filamentous fungus Podospora anserina, two phenomena are associated with polymorphism at the het-s locus, vegetative incompatibility and ascospore abortion. Two het-s alleles occur naturally, het-s and het-S. The het-s encoded protein is a prion propagating as a self-perpetuating amyloid aggregate. When prion-infected [Het-s] hyphae fuse with [Het-S] hyphae, the resulting heterokaryotic cells necrotize. [Het-s] and [Het-S] strains are sexually compatible. When, however, a female [Het-s] crosses with [Het-S], a significant percentage of het-S spores abort, in a way similar to spore killing in Neurospora and Podospora. We report here that sexual transmission of the [Het-s] prion after nonisogamous mating in the reproductive cycle of Podospora is responsible for the killing of het-S spores. Progeny of crosses between isogenic strains with distinct wild-type or introduced, ectopic het-s/S alleles were cytologically and genetically analyzed. The effect of het-s/S overexpression, ectopic het-s/S expression, absence of het-s expression, loss of [Het-s] prion infection, and the distribution patterns of HET-s/S-GFP proteins were categorized during meiosis and ascospore formation. This study unveiled a het-S spore-killing system that is governed by dosage of and interaction between the [Het-s] prion and the HET-S protein. Due to this property of the [Het-s] prion, the het-s allele acts as a meiotic drive element favoring maintenance of the prion-forming allele in natural populations.
XCLNCE; een spreadsheet voor het berekenen van stikstof en koolstof in de bodem
Zwart, K.B. - \ 2001
Wageningen : Alterra (Alterra-rapport 427) - 39
biologische landbouw - bodemvruchtbaarheid - elementen - stikstof - koolstof - computertechnieken - computer software - bemesting - bodem - nutriënten - organic farming - soil fertility - elements - nitrogen - carbon - computer techniques - computer software
XCLNCE is een Excel-spreadsheet voor het berekenen van de koolstof- en stikstofvoorraad in de bodem. XCLNCE is speciaal ontwikkeld voor de biolologische landbouw, maar kan ook voor andere teeltsystemen worden gebruikt. XCLNCE is gebaseerd op eenvoudige rekenregels en in dit rapport worden de structuur van de spreadsheet en enkele resultaten beschreven