| 1. |
- Becher, Paul G., et al.
(författare)
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Chemical signaling and insect attraction is a conserved trait in yeasts
- 2018
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; , s. 2962-2974
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Tidskriftsartikel (refereegranskat)abstract
- Yeast volatiles attract insects, which apparently is of mutual benefit, for both yeasts and insects. However, it is unknown whether biosynthesis of metabolites that attract insects is a basic and general trait, or if it is specific for yeasts that live in close association with insects. Our goal was to study chemical insect attractants produced by yeasts that span more than 250 million years of evolutionary history and vastly differ in their metabolism and lifestyle. We bioassayed attraction of the vinegar fly Drosophila melanogaster to odors of phylogenetically and ecologically distinct yeasts grown under controlled conditions. Baker's yeast Saccharomyces cerevisiae, the insect-associated species Candida californica, Pichia kluyveri and Metschnikowia andauensis, wine yeast Dekkera bruxellensis, milk yeast Kluyveromyces lactis, the vertebrate pathogens Candida albicans and Candida glabrata, and oleophilic Yarrowia lipolytica were screened for fly attraction in a wind tunnel. Yeast headspace was chemically analyzed, and co-occurrence of insect attractants in yeasts and flowering plants was investigated through a database search. In yeasts with known genomes, we investigated the occurrence of genes involved in the synthesis of key aroma compounds. Flies were attracted to all nine yeasts studied. The behavioral response to baker's yeast was independent of its growth stage. In addition to Drosophila, we tested the basal hexapod Folsomia candida (Collembola) in a Y-tube assay to the most ancient yeast, Y. lipolytica, which proved that early yeast signals also function on clades older than neopteran insects. Behavioral and chemical data and a search for selected genes of volatile metabolites underline that biosynthesis of chemical signals is found throughout the yeast clade and has been conserved during the evolution of yeast lifestyles. Literature and database reviews corroborate that yeast signals mediate mutualistic interactions between insects and yeasts. Moreover, volatiles emitted by yeasts are commonly found also in flowers and attract many insect species. The collective evidence suggests that the release of volatile signals by yeasts is a widespread and phylogenetically ancient trait, and that insect-yeast communication evolved prior to the emergence of flowering plants. Co-occurrence of the same attractant signals in yeast and flowers suggests that yeast-insect communication may have contributed to the evolution of insect-mediated pollination in flowers.
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| 2. |
- Becher, Paul, et al.
(författare)
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Yeast, not fruit volatiles mediate Drosophila melanogaster attraction, oviposition and development
- 2012
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 26:4, s. 822-828
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Tidskriftsartikel (refereegranskat)abstract
- 1.In nature, the fruit fly Drosophila melanogaster is attracted to fermenting fruit. Micro-organisms like Saccharomyces yeasts growing on fruit occupy a commonly overlooked trophic level between fruit and insects. Although the dietary quality of yeast is well established for D.melanogaster, the individual contribution of fruit and yeast on host finding and reproductive success has not been established. 2.Here, we show that baker's yeast Saccharomyces cerevisiae on its own is sufficient for fruit fly attraction, oviposition and larval development. In contrast, attraction and oviposition were significantly lower if non-fermented grape juice or growth media were used, and yeast-free grapes did not support larval development either. 3.Despite a strong preference for fermented substrates, moderate attraction to and oviposition on unfermented fruit might be adaptive in view of the fly's capacity to vector yeast. 4.Signals emitted by fruit were only of secondary importance because fermenting yeast without fruit induced the same fly behaviour as yeast fermenting on fruit. We identified a synthetic mimic of yeast odour, comprising ethanol, acetic acid, acetoin, 2-phenyl ethanol and 3-methyl-1-butanol, which was as attractive for the fly as fermenting grape juice or fermenting yeast minimal medium. 5.Yeast odours represent the critical signal to establish the flyfruityeast relationship. The traditional plantherbivore niche concept needs to be updated, to accommodate for the role of micro-organisms in insectplant interactions.
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| 3. |
- Clausen, Anders Ranegaard, et al.
(författare)
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Two thymidine kinases and one multisubstrate deoxyribonucleoside kinase salvage DNA precursors in Arabidopsis thaliana.
- 2012
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X. ; 279:20, s. 3889-3897
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Tidskriftsartikel (refereegranskat)abstract
- Deoxyribonucleotides are the building blocks of DNA and can be synthesized via de novo and salvage pathways. Deoxyribonucleoside kinases (dNKs) salvage deoxyribonucleosides by transfer of a phosphate group to the 5' of a deoxyribonucleoside. This salvage pathway is well characterized in mammals but in contrast little is known about how plants salvage deoxyribonucleosides. We show that during salvage, deoxyribonucleosides can be phosphorylated by extracts of Arabidopsis thaliana into corresponding mono-phosphate compounds with a surprising preference for purines over pyrimidines. Deoxyribonucleoside kinase activities were present in all tissues during all growth stages. In the A. thaliana genome we identified two types of genes that could encode enzymes which are involved in the salvage of deoxyribonucleosides. Thymidine kinase activity was encoded by two thymidine kinase 1-like genes (AtTK1a and AtTK1b) and deoxyadenosine, deoxyguanosine and deoxycytidine kinase activities were encoded by a single AtdNK gene. T-DNA insertion lines of AtTK1a and AtTK1b mutant genes had normal growth, but AtTK1a AtTK1b double mutants died at an early stage, which indicates that AtTK1a and AtTK1b catalyze redundant reactions. Our results point out a crucial role for salvage of thymidine during early plant development. © 2012 The Authors Journal compilation © 2012 FEBS.
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| 4. |
- Ishchuk, Olena P., et al.
(författare)
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Novel centromeric loci of the wine and beer yeast dekkera bruxellensis CEN1 and CEN2
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- The wine and beer yeast Dekkera bruxellensis thrives in environments that are harsh and limiting, especially in concentrations with low oxygen and high ethanol. Its different strains' chromosomes greatly vary in number (karyotype). This study isolates two novel centromeric loci (CEN1 and CEN2), which support both the yeast's autonomous replication and the stable maintenance of plasmids. In the sequenced genome of the D. bruxellensis strain CBS 2499, CEN1 and CEN2 are each present in one copy. They differ from the known "point" CEN elements, and their biological activity is retained within ~900-1300 bp DNA segments. CEN1 and CEN2 have features of both "point" and "regional" centromeres: They contain conserved DNA elements, ARSs, short repeats, one tRNA gene, and transposon-like elements within less than 1 kb. Our discovery of a miniature inverted-repeat transposable element (MITE) next to CEN2 is the first report of such transposons in yeast. The transformants carrying circular plasmids with cloned CEN1 and CEN2 undergo a phenotypic switch: They form fluffy colonies and produce three times more biofilm. The introduction of extra copies of CEN1 and CEN2 promotes both genome rearrangements and ploidy shifts, with these effects mediated by homologous recombination (between circular plasmid and genome centromere copy) or by chromosome breakage when integrated. Also, the proximity of the MITE-like transposon to CEN2 could translocate CEN2 within the genome or cause chromosomal breaks, so promoting genome dynamics. With extra copies of CEN1 and CEN2, the yeast's enhanced capacities to rearrange its genome and to change its gene expression could increase its abilities for exploiting new and demanding niches.
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| 5. |
- Khan, Zahidul, et al.
(författare)
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Plant thymidine kinase 1: a novel efficient suicide gene for malignant glioma therapy.
- 2010
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Ingår i: Neuro-Oncology. - : Oxford University Press (OUP). - 1523-5866 .- 1522-8517. ; 12, s. 549-558
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Tidskriftsartikel (refereegranskat)abstract
- The prognosis for malignant gliomas remains poor, and new treatments are urgently needed. Targeted suicide gene therapy exploits the enzymatic conversion of a prodrug, such as a nucleoside analog, into a cytotoxic compound. Although this therapeutic strategy has been considered a promising regimen for central nervous system (CNS) tumors, several obstacles have been encountered such as inefficient gene transfer to the tumor cells, limited prodrug penetration into the CNS, and inefficient enzymatic activity of the suicide gene. We report here the cloning and successful application of a novel thymidine kinase 1 (TK1) from the tomato plant, with favorable characteristics in vitro and in vivo. This enzyme (toTK1) is highly specific for the nucleoside analog prodrug zidovudine (azidothymidine, AZT), which is known to penetrate the blood-brain barrier. An important feature of toTK1 is that it efficiently phosphorylates its substrate AZT not only to AZT monophosphate, but also to AZT diphosphate, with excellent kinetics. The efficiency of the toTK1/AZT system was confirmed when toTK1-transduced human glioblastoma (GBM) cells displayed a 500-fold increased sensitivity to AZT compared with wild-type cells. In addition, when neural progenitor cells were used as delivery vectors for toTK1 in intracranial GBM xenografts in nude rats, substantial attenuation of tumor growth was achieved in animals exposed to AZT, and survival of the animals was significantly improved compared with controls. The novel toTK1/AZT suicide gene therapy system in combination with stem cell-mediated gene delivery promises new treatment of malignant gliomas.
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| 6. |
- Knecht, W., et al.
(författare)
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Drosophila deoxyribonucleoside kinase mutants with enhanced ability to phosphorylate purine analogs
- 2007
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Ingår i: Gene Therapy. - : Springer Science and Business Media LLC. - 0969-7128 .- 1476-5462. ; 14:17, s. 1278-1286
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Tidskriftsartikel (refereegranskat)abstract
- Transduced deoxyribonucleoside kinases (dNK) can be used to kill recipient cells in combination with nucleoside prodrugs. The Drosophila melanogaster multisubstrate dNK (Dm-dNK) displays a superior turnover rate and has a great plasticity regarding its substrates. We used directed evolution to create Dm-dNK mutants with increased specificity for several nucleoside analogs (NAs) used as anticancer or antiviral drugs. Four mutants were characterized for the ability to sensitize Escherichia coli toward analogs and for their substrate specificity and kinetic parameters. The mutants had a reduced ability to phosphorylate pyrimidines, while the ability to phosphorylate purine analogs was relatively similar to the wild-type enzyme. We selected two mutants, for expression in the osteosarcoma 143B, the glioblastoma U-87M-G and the breast cancer MCF7 cell lines. The sensitivities of the transduced cell lines in the presence of the NAs fludarabine (F-AraA), cladribine (CdA), vidarabine and cytarabine were compared to the parental cell lines. The sensitivity of 143B cells was increased by 470-fold in the presence of CdA and of U-87M-G cells by 435fold in the presence of F-AraA. We also show that a choice of the selection and screening system plays a crucial role when optimizing suicide genes by directed evolution.
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| 7. |
- Martín, Juan A, et al.
(författare)
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Resistance to Dutch elm disease reduces presence of xylem endophytic fungi in Elms (Ulmus spp.)
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Efforts to introduce pathogen resistance into landscape tree species by breeding may have unintended consequences for fungal diversity. To address this issue, we compared the frequency and diversity of endophytic fungi and defensive phenolic metabolites in elm (Ulmus spp.) trees with genotypes known to differ in resistance to Dutch elm disease. Our results indicate that resistant U. minor and U. pumila genotypes exhibit a lower frequency and diversity of fungal endophytes in the xylem than susceptible U. minor genotypes. However, resistant and susceptible genotypes showed a similar frequency and diversity of endophytes in the leaves and bark. The resistant and susceptible genotypes could be discriminated on the basis of the phenolic profile of the xylem, but not on basis of phenolics in the leaves or bark. As the Dutch elm disease pathogen develops within xylem tissues, the defensive chemistry of resistant elm genotypes thus appears to be one of the factors that may limit colonization by both the pathogen and endophytes. We discuss a potential trade-off between the benefits of breeding resistance into tree species, versus concomitant losses of fungal endophytes and the ecosystem services they provide.
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| 8. |
- Piskur, Jure, et al.
(författare)
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How did Saccharomyces evolve to become a good brewer?
- 2006
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Ingår i: Trends in Genetics. - : Elsevier BV. - 1362-4555 .- 0168-9525. ; 22:4, s. 183-186
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Tidskriftsartikel (refereegranskat)abstract
- Brewing and wine production are among the oldest technologies and their products are almost indispensable in our lives. The central biological agents of beer and wine fermentation are yeasts belonging to the genus Saccharomyces, which can accumulate ethanol. Recent advances in comparative genomics and bioinformatics have made it possible to elucidate when and why yeasts produce ethanol in high concentrations, and how this remarkable trait originated and developed during their evolutionary history. Two research groups have shed light on the origin of the genes encoding alcohol dehydrogenase and the process of ethanol accumulation in Saccharomyces cerevisiae.
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| 9. |
- Rozpedowska, Elzbieta, et al.
(författare)
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Candida albicans- a pre-whole genome duplication yeast is predominantly aerobic and a poor ethanol producer.
- 2011
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 11:3, s. 285-291
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Tidskriftsartikel (refereegranskat)abstract
- Yeast species belonging to the lineage that underwent the whole genome duplication (WGD), and including Saccharomyces cerevisiae, can grow under anaerobiosis and accumulate ethanol in the presence of glucose and oxygen. The pre-WGD yeasts, which branched from the S. cerevisiae lineage just prior to the WGD event, including Kluyveromyces lactis, are more dependent on oxygen and do not accumulate large amounts of ethanol in the presence of excess oxygen. Yeasts that belong to the so-called 'lower branches' of the yeast phylogenetic tree and diverged from S. cerevisiae more than 200 million years ago, have so far not been thoroughly investigated for their physiology and carbon metabolism. We have hereby studied several isolates of Candida albicans and Debaryomyces hansenii for their dependence on oxygen. C. albicans grew very poorly at oxygen concentration below 1 p.p.m. and D. hansenii could not grow at all. In aerobic batch cultivations C. albicans exhibited a predominately aerobic metabolism, accumulating only small amounts of ethanol (0.01-0.09 g g(-1) glucose). Apparently, C. albicans and several other pre-WGD yeasts still exhibit the original traits of the yeast progenitor: poor accumulation of ethanol under aerobic conditions and strong dependence on the presence of oxygen.
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| 10. |
- Rozpedowska, Elzbieta
(författare)
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Genomics and Evolution Studies of Dekkera bruxellensis, a Wine-Spoilage Yeast
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Yeasts are unicellular fungi exhibiting a huge diversity of life styles and physiologies and their evolutionary span exceeds the one between mammals and unchordates. The recent advances in genome sequencing and comparative genomics accelerated genomic, evolutionary and physiological studies of yeasts, making them a very promising model to study eukaryotic cell, and also deepened our understanding of the molecular background of yeasts physiologies. The most extensively studied yeasts species Saccharomyces cerevisiae, and its close relatives, exhibit several unique physiological characteristics like (i) ethanol production under aerobic conditions (Crabtree effect), (ii) ability to grow in almost total absence of oxygen and (iii) the ability to generate respiratory deficient (petite) mutants. These traits form a frame for the development of the so-called “make-accumulate-consume” strategy, which helps Saccharomyces yeasts to out-compete other microbes when a lot of sugars are present in the environment. Several molecular events contributed to the above mentioned characteristics of modern yeasts, among them the whole genome duplication (WGD), rewiring of the expression network, horizontal gene transfer and the duplication of the gene coding for alcohol dehydrogenase. However, even though S. cerevisiae reached perfection in efficient ethanol production and ability to grow anaerobically, apparently it is not unique among yeasts. Dekkera bruxellensis that diverged from S. cerevisiae more than 200 mya is also an efficient ethanol producer and can grow anaerobically. We show that the same molecular mechanism was involved independently in the development of the “make-accumulate-consume” strategy in both lineages. In other words, both yeast lineages followed a parallel evolutionary path to reach the same phenotype. A relative of D. bruxellensis, the human pathogen Candida albicans that belongs to the pre-WGD group is unable of efficient aerobic ethanol production and cannot grow in anaerobiosis. It grows rapidly in aerobic conditions, using the carbon source on biomass production and not on alcohol synthesis. We prove that C. albicans exhibits the Crabtree negative phenotype and is obligate aerobe, two traits characteristic for the progenitor of the modern yeasts.
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