The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Regine Kahmann - One of the best experts on this subject based on the ideXlab platform.
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A model of Ustilago maydis leaf tumor metabolism
Plant signaling & behavior, 2010Co-Authors: Robin J. Horst, Gunther Doehlemann, Regine Kahmann, Jörg Kämper, Ramon Wahl, Jörg Hofmann, Alfred Schmiedl, Lars M. VollAbstract:Extensive progress has been made in the last years in unraveling molecular mechanisms of plant-pathogen interactions. Although the main research focus lies on defense and counter-defense mechanisms, some plant-pathogen interactions have been characterized on the physiological level. Only a few studies have focused on the nutrient acquisition strategies of phytopathogens. In a previous study, we analyzed how local infection of maize leaves by the tumor-inducing fungus Ustilago maydis affects whole plant physiology and were able to show that carbon and nitrogen assimilates are rerouted to the tumor. While the sink strength of infected emerging young leaves increases with tumor development, systemic source leaves exhibit elevated export of assimilates and delayed senescence to compensate for the altered sink-source balance. Here we provide new experimental data on the metabolization of these assimilates in the tumor and propose a model on their utilization in the infected tissue.
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Ustilago maydis as a Pathogen
Annual review of phytopathology, 2009Co-Authors: Thomas Brefort, Stefanie Reissmann, Gunther Doehlemann, Artemio Mendoza-mendoza, Armin Djamei, Regine KahmannAbstract:The Ustilago maydis-maize pathosystem has emerged as the current model for plant pathogenic basidiomycetes and as one of the few models for a true biotrophic interaction that persists throughout fungal development inside the host plant. This is based on the highly advanced genetic system for both the pathogen and its host, the ability to propagate U. maydis in axenic culture, and its unique capacity to induce prominent disease symptoms (tumors) on all aerial parts of maize within less than a week. The corn smut pathogen, though economically not threatening, will continue to serve as a model for related obligate biotrophic fungi such as the rusts, but also for closely related smut species that induce symptoms only in the flower organs of their hosts. In this review we describe the most prominent features of the U. maydis-maize pathosystem as well as genes and pathways most relevant to disease. We highlight recent developments that place this system at the forefront of understanding the function of secreted effectors in eukaryotic pathogens and describe the expected spin-offs for closely related species exploiting comparative genomics approaches.
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The secretome of the maize pathogen Ustilago maydis.
Fungal Genetics and Biology, 2008Co-Authors: Olaf Mueller, Regine Kahmann, Guillermo Aguilar, Blanca Trejo-aguilar, Ronald P. De VriesAbstract:Ustilago maydis establishes a biotrophic relationship with its host plant, i.e. plant cells stay alive despite massive fungal growth in infected tissue. The genome sequence has revealed that U. maydis is poorly equipped with plant cell wall degrading enzymes and uses novel secreted protein effectors as crucial determinants for biotrophic development. Many of these effector genes are clustered and differentially regulated during plant colonization. In this review, we analyze the secretome of U. maydis by differentiating between secreted enzymes, likely structural proteins of the fungal cell wall (excluding GPI-anchored proteins) as well as likely effectors with either apoplastic or cytoplasmic function. This classification is based on the presence of functional domains, general domain structure and cysteine pattern. In addition, we discuss possible functions of selected protein classes with a special focus on disease development.
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Ustilago maydis : how its biology relates to pathogenic development
New Phytologist, 2004Co-Authors: Regine Kahmann, Jörg KämperAbstract:Contents Summary I. Introduction II. Important tools for exprimentation with Ustilago myadis III. Cell fusion requres a complex signalling network IV. Development of the dikaryon: the bE/bW complex at work V. A connection between cell cycle, morphogenesis and virulence VI. The early infection stages VII. Proliferation and differentiaton in the plant host VIII. The Ustilago maydis genome IX. Conclusions Acknowledgements References Summary The smut fungus Ustilago maydis is a ubiquitous pathogen of corn. Although of minor economical importance, U. maydis has become the most attractive model among the plant pathogenic basidiomycetes under study. This fungus undergoes a number of morphological transitions throughout its life-cycle, the most prominent being the dimorphic switch from budding to filamentous growth that is prerequisite for entry into the biotrophic phase. The morphological transition is controlled by the tetrapolar mating system. Understanding the mating system has allowed connections to signalling cascades operating during pathogenic development. Here, we will review the status and recent insights into understanding pathogenic development of U. maydis and emphasize areas and directions of future research.
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Regulation of mating and pathogenic development in Ustilago maydis.
Current opinion in microbiology, 2004Co-Authors: Michael Feldbrügge, Jörg Kämper, Gero Steinberg, Regine KahmannAbstract:The plant pathogenic fungus Ustilago maydis induces disease only in its dikaryotic stage that is generated after mating. This process involves coordinated cAMP and mitogen-activated protein kinase signalling to regulate transcriptional as well as morphological responses. Among the induced products is the key regulator for pathogenic development. Recent advances identified crucial nodes that interconnect these pathways. The key regulator orchestrates a complex transcriptional cascade, the components of which have been uncovered by genomic strategies. This is complemented by insights into organization, dynamics and function of the cytoskeleton, which begin to establish the links between signalling, intracellular transport processes and morphology.
Nicole Ludwig - One of the best experts on this subject based on the ideXlab platform.
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Ustilago maydis effectors and their impact on virulence
Nature Reviews Microbiology, 2017Co-Authors: Daniel Lanver, Shigeyuki Tanaka, Stefanie Reissmann, Marie Tollot, Gabriel Schweizer, Libera Lo Presti, Lay-sun Ma, Mariana Schuster, Liang Liang, Nicole LudwigAbstract:Biotrophic fungal plant pathogens establish an intimate relationship with their host to support the infection process. Central to this strategy is the secretion of a range of protein effectors that enable the pathogen to evade plant immune defences and modulate host metabolism to meet its needs. In this Review, using the smut fungus Ustilago maydis as an example, we discuss new insights into the effector repertoire of smut fungi that have been gained from comparative genomics and discuss the molecular mechanisms by which U. maydis effectors change processes in the plant host. Finally, we examine how the expression of effector genes and effector secretion are coordinated with fungal development in the host. Ustilago maydis is a member of the smut fungi (phylum Basidiomycota) that infect maize. This group of plant pathogens is characterized by their biotrophic lifestyle and narrow host range. The establishment of a biotrophic, compatible interaction between U. maydis and maize depends on the secretion of specialized fungal proteins termed effectors. A large proportion of these effectors are completely novel, as they do not contain any annotated domains, and most of them are species-specific or lineage-specific. Many of the novel effector genes are arranged in gene clusters, which arose through gene duplications and represent genomic islands with accelerated evolution. Many of these clusters are important for virulence. Effector genes that markedly contribute to virulence are conserved among the smut fungi. For a few effectors their mode of action has been elucidated. They counteract defence responses, re-route metabolic pathways and stimulate plant cell division. The expression of effector genes is regulated by a hierarchical network of transcription factors and is coupled to sexual development and spore formation. The plant signals that induce the expression of effector genes are largely unknown. Biotrophic fungal plant pathogens secrete protein effectors that support colonization of the host. Here, Kahmann and colleagues discuss new insights into the effector repertoire of smut fungi, the molecular mechanisms whereby effectors of Ustilago maydis change plant cell processes, how the respective genes are regulated and how effectors evolve.
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Ustilago maydis effectors and their impact on virulence.
Nature reviews. Microbiology, 2017Co-Authors: Daniel Lanver, Shigeyuki Tanaka, Stefanie Reissmann, Marie Tollot, Gabriel Schweizer, Mariana Schuster, Liang Liang, Libera Lo Presti, Nicole LudwigAbstract:Biotrophic fungal plant pathogens establish an intimate relationship with their host to support the infection process. Central to this strategy is the secretion of a range of protein effectors that enable the pathogen to evade plant immune defences and modulate host metabolism to meet its needs. In this Review, using the smut fungus Ustilago maydis as an example, we discuss new insights into the effector repertoire of smut fungi that have been gained from comparative genomics and discuss the molecular mechanisms by which U. maydis effectors change processes in the plant host. Finally, we examine how the expression of effector genes and effector secretion are coordinated with fungal development in the host.
Gunther Doehlemann - One of the best experts on this subject based on the ideXlab platform.
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Transcriptome analysis in the maize-Ustilago maydis interaction identifies maize-line-specific activity of fungal effectors
2020Co-Authors: S. Schurack, Marco Thines, Jasper R.l. Depotter, Deepak K. Gupta, Gunther DoehlemannAbstract:The biotrophic pathogen The biotrophic pathogen Ustilago maydis causes smut disease on maize (Zea mays) and induces the formation of tumours on all aerial parts of the plant. Unlike in other biotrophic interactions, no gene-for-gene interactions have been identified in the maize-U. maydis pathosystem. Thus, maize resistance to Ustilago maydis is considered a polygenic, quantitative trait. Here, we study the molecular mechanisms of quantitative disease resistance (QDR) in maize, and how Ustilago maydis interferes with its components. Based on quantitative scoring of disease symptoms in 26 maize lines, we performed an RNA-Seq analysis of six Ustilago maydis -infected maize lines of highly distinct resistance levels. In accordance with the complex nature of QDR, the different maize lines showed specific responses of diverse cellular processes to Ustilago maydis infection. On the pathogen side, our analysis identified 406 Ustilago maydis genes being differentially expressed between maize lines, of which 102 encode predicted effector proteins. Based on this analysis, we generated Ustilago maydis CRISPR/Cas9 knockout mutants for selected candidate effector sets. Infections of different maize lines with the fungal mutants and subsequent RNA-sequencing identified effectors with quantitative, maize-line-specific virulence functions, and revealed auxin-related processes as a possible target for one of them. Thus, we show that both transcriptional activity and virulence function of fungal effector genes are modified according to the infected maize line, providing new insights into the molecular mechanisms underlying QDR in the maize-Ustilago maydis interaction.
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Cas9HF1 enhanced specificity in Ustilago maydis
2019Co-Authors: Weiliang Zuo, Jasper R.l. Depotter, Gunther DoehlemannAbstract:Abstract The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system is widely used as a tool to precisely manipulate genomic sequence targeted by sgRNA (single guide RNA) and is adapted in different species for genome editing. One of the major concerns of CRISPR-Cas9 is the possibility of off-target effects, which can be remedied by the deployment of high fidelity Cas9 variants. Ustilago maydis is a maize fungal pathogen, which has served as a model organism for biotrophic pathogens for decades. The successful adaption of CRISPR-Cas9 in U. maydis greatly facilitated effector biology studies. Here, we constructed an U. maydis reporter strain that allows in vivo quantification of efficiency and target specificity of three high fidelity Cas9 variants, Cas9HF1, Cas9esp1.1 and Cas9hypa. This approach identified Cas9HF1 as most specific Cas9 variant in U. maydis. Furthermore, whole genome sequencing showed absence of off-target effects in U. maydis by CRISPR-Cas9 editing.
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virulence of the maize smut Ustilago maydis is shaped by organ specific effectors
Molecular Plant Pathology, 2014Co-Authors: Lena Schilling, Alexandra Matei, Amey Redkar, Virginia Walbot, Gunther DoehlemannAbstract:Summary With the exception of Ustilago maydis, smut fungi infecting monocotyledonous hosts systemically colonize infected plants and cause symptoms exclusively in the inflorescences. Ustilago maydis infects primordia of all aerial organs of maize (Zea mays L.) and results in the formation of large plant tumours. Previously, we have found that U. maydis infection of seedling leaves, adult leaves and tassels causes organ-specific transcriptional changes in both the pathogen and the host. Of particular interest, U. maydis genes encoding secreted proteins are differentially expressed depending on the colonized maize organ. Therefore, we hypothesized that the fungus secretes virulence-related proteins (effectors) that act in an organ-specific manner. Here, we present the identification and functional characterization of 20 presumptive organ-specific U. maydis effector genes. Ustilago maydis deletion strains for these genes were generated and tested for infectivity of maize seedling leaves and tassels. This approach identified 11 effector genes required for the full virulence of U. maydis. In nine cases, virulence was only affected in one of the tested plant organs. These results demonstrate that individual fungal effector proteins contribute to fungal virulence in an organ-specific manner.
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A model of Ustilago maydis leaf tumor metabolism
Plant signaling & behavior, 2010Co-Authors: Robin J. Horst, Gunther Doehlemann, Regine Kahmann, Jörg Kämper, Ramon Wahl, Jörg Hofmann, Alfred Schmiedl, Lars M. VollAbstract:Extensive progress has been made in the last years in unraveling molecular mechanisms of plant-pathogen interactions. Although the main research focus lies on defense and counter-defense mechanisms, some plant-pathogen interactions have been characterized on the physiological level. Only a few studies have focused on the nutrient acquisition strategies of phytopathogens. In a previous study, we analyzed how local infection of maize leaves by the tumor-inducing fungus Ustilago maydis affects whole plant physiology and were able to show that carbon and nitrogen assimilates are rerouted to the tumor. While the sink strength of infected emerging young leaves increases with tumor development, systemic source leaves exhibit elevated export of assimilates and delayed senescence to compensate for the altered sink-source balance. Here we provide new experimental data on the metabolization of these assimilates in the tumor and propose a model on their utilization in the infected tissue.
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Ustilago maydis as a Pathogen
Annual review of phytopathology, 2009Co-Authors: Thomas Brefort, Stefanie Reissmann, Gunther Doehlemann, Artemio Mendoza-mendoza, Armin Djamei, Regine KahmannAbstract:The Ustilago maydis-maize pathosystem has emerged as the current model for plant pathogenic basidiomycetes and as one of the few models for a true biotrophic interaction that persists throughout fungal development inside the host plant. This is based on the highly advanced genetic system for both the pathogen and its host, the ability to propagate U. maydis in axenic culture, and its unique capacity to induce prominent disease symptoms (tumors) on all aerial parts of maize within less than a week. The corn smut pathogen, though economically not threatening, will continue to serve as a model for related obligate biotrophic fungi such as the rusts, but also for closely related smut species that induce symptoms only in the flower organs of their hosts. In this review we describe the most prominent features of the U. maydis-maize pathosystem as well as genes and pathways most relevant to disease. We highlight recent developments that place this system at the forefront of understanding the function of secreted effectors in eukaryotic pathogens and describe the expected spin-offs for closely related species exploiting comparative genomics approaches.
Jörg Kämper - One of the best experts on this subject based on the ideXlab platform.
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Galactose metabolism and toxicity in Ustilago maydis.
Fungal genetics and biology : FG & B, 2018Co-Authors: David Schuler, Lars M. Voll, Christina Höll, Nathalie Grün, Jonas Ulrich, Bastian Dillner, Franz Klebl, Alexandra Ammon, Jörg KämperAbstract:In most organisms, galactose is metabolized via the Leloir pathway, which is conserved from bacteria to mammals. Utilization of galactose requires a close interplay of the metabolic enzymes, as misregulation or malfunction of individual components can lead to the accumulation of toxic intermediate compounds. For the phytopathogenic basidiomycete Ustilago maydis, galactose is toxic for wildtype strains, i.e. leads to growth repression despite the presence of favorable carbon sources as sucrose. The galactose sensitivity can be relieved by two independent modifications: (1) by disruption of Hxt1, which we identify as the major transporter for galactose, and (2) by a point mutation in the gene encoding the galactokinase Gal1, the first enzyme of the Leloir pathway. The mutation in gal1(Y67F) leads to reduced enzymatic activity of Gal1 and thus may limit the formation of putatively toxic galactose-1-phosphate. However, systematic deletions and double deletions of different genes involved in galactose metabolism point to a minor role of galactose-1-phosphate in galactose toxicity. Our results show that molecular triggers for galactose toxicity in U. maydis differ from yeast and mammals.
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A model of Ustilago maydis leaf tumor metabolism
Plant signaling & behavior, 2010Co-Authors: Robin J. Horst, Gunther Doehlemann, Regine Kahmann, Jörg Kämper, Ramon Wahl, Jörg Hofmann, Alfred Schmiedl, Lars M. VollAbstract:Extensive progress has been made in the last years in unraveling molecular mechanisms of plant-pathogen interactions. Although the main research focus lies on defense and counter-defense mechanisms, some plant-pathogen interactions have been characterized on the physiological level. Only a few studies have focused on the nutrient acquisition strategies of phytopathogens. In a previous study, we analyzed how local infection of maize leaves by the tumor-inducing fungus Ustilago maydis affects whole plant physiology and were able to show that carbon and nitrogen assimilates are rerouted to the tumor. While the sink strength of infected emerging young leaves increases with tumor development, systemic source leaves exhibit elevated export of assimilates and delayed senescence to compensate for the altered sink-source balance. Here we provide new experimental data on the metabolization of these assimilates in the tumor and propose a model on their utilization in the infected tissue.
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Ustilago maydis : how its biology relates to pathogenic development
New Phytologist, 2004Co-Authors: Regine Kahmann, Jörg KämperAbstract:Contents Summary I. Introduction II. Important tools for exprimentation with Ustilago myadis III. Cell fusion requres a complex signalling network IV. Development of the dikaryon: the bE/bW complex at work V. A connection between cell cycle, morphogenesis and virulence VI. The early infection stages VII. Proliferation and differentiaton in the plant host VIII. The Ustilago maydis genome IX. Conclusions Acknowledgements References Summary The smut fungus Ustilago maydis is a ubiquitous pathogen of corn. Although of minor economical importance, U. maydis has become the most attractive model among the plant pathogenic basidiomycetes under study. This fungus undergoes a number of morphological transitions throughout its life-cycle, the most prominent being the dimorphic switch from budding to filamentous growth that is prerequisite for entry into the biotrophic phase. The morphological transition is controlled by the tetrapolar mating system. Understanding the mating system has allowed connections to signalling cascades operating during pathogenic development. Here, we will review the status and recent insights into understanding pathogenic development of U. maydis and emphasize areas and directions of future research.
-
Regulation of mating and pathogenic development in Ustilago maydis.
Current opinion in microbiology, 2004Co-Authors: Michael Feldbrügge, Jörg Kämper, Gero Steinberg, Regine KahmannAbstract:The plant pathogenic fungus Ustilago maydis induces disease only in its dikaryotic stage that is generated after mating. This process involves coordinated cAMP and mitogen-activated protein kinase signalling to regulate transcriptional as well as morphological responses. Among the induced products is the key regulator for pathogenic development. Recent advances identified crucial nodes that interconnect these pathways. The key regulator orchestrates a complex transcriptional cascade, the components of which have been uncovered by genomic strategies. This is complemented by insights into organization, dynamics and function of the cytoskeleton, which begin to establish the links between signalling, intracellular transport processes and morphology.
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Heterologous transposition in Ustilago maydis.
Molecular genetics and genomics : MGG, 2003Co-Authors: Oliver Ladendorf, Andreas Brachmann, Jörg KämperAbstract:The phytopathogenic basidiomycete Ustilago maydis has become a model system for the analysis of plant-pathogen interactions. The genome sequence of this organism will soon be available, increasing the need for techniques to analyse gene function on a broad basis. We describe a heterologous transposition system for U. maydis that is based on the Caenorhabditis transposon Tc1, which is known to function independently of host factors and to be active in evolutionarily distant species. We have established a nitrate reductase based two-component counterselection system to screen for Tc1 transposition. The element was shown to be functional and transposed to several different locations in the genome of U. maydis. The insertion pattern observed was consistent with the proposed general mechanism of Tc1/mariner integration and constitutes a proof of principle for the first heterologous transposition system in a basidiomycete species. By mapping the insertion site context to known genomic sequences, Tc1 insertion events were shown to occur on different chromosomes, but exhibit a preference for non-coding regions. Only 20% of the insertions were found in putative open reading frames. The establishment of this system will permit efficient gene tagging in U. maydis and possibly also in other fungi.
William K. Holloman - One of the best experts on this subject based on the ideXlab platform.
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structurally distinct telomere binding proteins in Ustilago maydis execute non overlapping functions in telomere replication recombination and protection
Communications Biology, 2020Co-Authors: Syed S Zahid, William K. Holloman, Swapna Ganduri, Jeanette H Sutherland, Min Hsu, Neal F LueAbstract:Duplex telomere binding proteins exhibit considerable structural and functional diversity in fungi. Herein we interrogate the activities and functions of two Myb-containing, duplex telomere repeat-binding factors in Ustilago maydis, a basidiomycete that is evolutionarily distant from the standard fungi. These two telomere-binding proteins, UmTay1 and UmTrf2, despite having distinct domain structures, exhibit comparable affinities and sequence specificity for the canonical telomere repeats. UmTay1 specializes in promoting telomere replication and an ALT-like pathway, most likely by modulating the helicase activity of Blm. UmTrf2, in contrast, is critical for telomere protection; transcriptional repression of Umtrf2 leads to severe growth defects and profound telomere aberrations. Comparative analysis of UmTay1 homologs in different phyla reveals broad functional diversity for this protein family and provides a case study for how DNA-binding proteins can acquire and lose functions at various chromosomal locations. Our findings also point to stimulatory effect of telomere protein on ALT in Ustilago maydis that may be conserved in other systems. Yu et al. provide evidence that Ustilago maydis employs two structurally distinct telomere-binding proteins to perform complementary functions in telomere maintenance in this organism. While UmTay1 regulates primarily telomere replication and recombination, UmTrf2 is responsible for telomere protection.
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The homologous recombination system of Ustilago maydis
Fungal Genetics and Biology, 2008Co-Authors: William K. Holloman, Jan Schirawski, Robin HollidayAbstract:Abstract Homologous recombination is a high fidelity, template-dependent process that is used in repair of damaged DNA, recovery of broken replication forks, and disjunction of homologous chromosomes in meiosis. Much of what is known about recombination genes and mechanisms comes from studies on baker’s yeast. Ustilago maydis, a basidiomycete fungus, is distant evolutionarily from baker’s yeast and so offers the possibility of gaining insight into recombination from an alternative perspective. Here we have surveyed the genome of U. maydis to determine the composition of its homologous recombination system. Compared to baker’s yeast, there are fundamental differences in the function as well as in the repertoire of dedicated components. These include the use of a BRCA2 homolog and its modifier Dss1 rather than Rad52 as a mediator of Rad51, the presence of only a single Rad51 paralog, and the absence of Dmc1 and auxiliary meiotic proteins.
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Shuttle vectors for genetic manipulations in Ustilago maydis.
Canadian journal of microbiology, 2000Co-Authors: Milorad Kojic, William K. HollomanAbstract:Shuttle vectors with new or improved features were constructed to enable facile genetic manipulations in the plant pathogen Ustilago maydis. Sets of plasmids selectable in media containing geneticin, carboxin, nourseothricin, or hygromycin, able to replicate autonomously, to transform U. maydis by integration, and to express foreign genes under control of the homologous glyceraldehyde-3-phosphate dehydrogenase promoter, were built upon a common pUC19 vector backbone. This permits a large number of choices for a cloning site, blue/white screening for recombinant plasmids, rapid transfer of a cloned DNA fragment between plasmids, and choice of several dominant drug-resistance markers for selection in U. maydis.
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The LEU1 gene of Ustilago maydis.
Gene, 1994Co-Authors: Brian P. Rubin, William K. HollomanAbstract:Abstract The nucleotide sequence of the Ustilago maydis LEU1 gene has been determined. It contains a continuous open reading frame predicted to encode a protein of 773 amino acids with a molecular mass of 83 234 Da. The protein is homologous to α-isopropylmalate isomerases from prokaryotes and eukaryotes, as well as to other members of a family of structurally related isomerases.
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Purification and properties of a cruciform DNA binding protein from Ustilago maydis
Chromosoma, 1993Co-Authors: Hidehito Kotani, Eric B. Kmiec, William K. HollomanAbstract:A DNA binding protein with an M(r) of 11,000 was purified from Ustilago maydis. Its solubility in acid, amino acid composition, and mobility during gel electrophoresis are reminiscent of properties observed for the high mobility group nonhistone chromosomal proteins. The protein recognizes cruciform DNA made from oligonucleotides and also binds preferentially to a plasmid containing an extruded cruciform.
