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Gaca, The Response Regulator Of A Two-Component System, Acts As A Master Regulator In Pseudomonas Syringae Pv. Tomato Dc3000 By Controlling Regulatory Rna, Transcriptional Activators, And Alternate Sigma Factors, Asita Chatterjee, Yaya Cui, Hailian Yang, Alan Collmer, James R. Alfano, Arun K. Chatterjee

Department of Plant Pathology: Faculty Publications

Concerted investigations of factors affecting host-pathogen interactions are now possible with the model plant Arabidopsis thaliana and its model pathogen Pseudomonas syringae pv. tomato DC3000, as their whole genome sequences have become available. As a prelude to analysis of the regulatory genes and their targets, we have focused on GacA, the response regulator of a two-component system. The DC3000 gene was cloned by testing for the reversal of phenotypes of an Erwinia GacA– mutant. A GacA– mutant of DC3000 constructed by marker exchange produces much-reduced levels of transcripts of three alternate sigma factors: HrpL, required for the production of effector …

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The Complete Genome Sequence Of The Arabidopsis And Tomato Pathogen Pseudomonas Syringae Pv. Tomato Dc3000, C. Robin Buell, Vinita Joardar, Magdalen Lindeberg, Jeremy Selengut, Ian T. Paulsen, Michelle L. Gwinn, Robert J. Dodson, Robert T. Deboy, A. Scott Durkin, James F. Kolonay, Ramana Radupu, Sean Daugherty, Lauren Brinkac, Maureen J. Beanan, Daniel H. Haft, William C. Nelson, Tanja Davidsen, Nikhat Zafar, Liwei Zhou, Jia Liu, Qiaoping Yuan, Hoda Khouri, Nadia Fedorova, Bao Tran, Daniel Russell, Kristi Berry, Teresa Utterback, Susan E. Van Aken, Tamara V. Feldblyum, Mark D'Ascenzo, Wen-Ling Deng, Adela R. Ramos, James R. Alfano, Samuel Cartinhour, Arn K. Chatterjee, Terrence P. Delaney, Sondra G. Lazarowitz, Gregory B. Martin, David J. Schneider, Xiaoyan Tang, Carol L. Bender, Owen White, Claire M. Fraser, Alan Collmer

Department of Plant Pathology: Faculty Publications

We report the complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana. The DC3000 genome (6.5 megabases) contains a circular chromosome and two plasmids, which collectively encode 5,763 ORFs. We identified 298 established and putative virulence genes, including several clusters of genes encoding 31 confirmed and 19 predicted type III secretion system effector proteins. Many of the virulence genes were members of paralogous families and also were proximal to mobile elements, which collectively comprise7%of the DC3000 genome. The bacterium possesses a large repertoire of transporters for …

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Effects Of Modification Of The Transcription Initiation Site Context On Citrus Tristeza Virus Subgenomic Rna Synthesis, Maria A. Ayllon, Siddarame Gowda, Satyanarayana Tatineni, Alexander V. Karasev, Scott Adkins, Munir Mawassi, Jose Guerri, Pedro Moreno, William O. Dawson

Department of Plant Pathology: Faculty Publications

Citrus tristeza virus (CTV), a member of the Closteroviridae, has a positive-sense RNA genome of about 20 kb organized into 12 open reading frames (ORFs). The last 10 ORFs are expressed through 3'-coterminal subgenomic RNAs (sgRNAs) regulated in both amounts and timing. Additionally, relatively large amounts of complementary sgRNAs are produced. We have been unable to determine whether these sgRNAs are produced by internal promotion from the full-length template minus strand or by transcription from the minus-stranded sgRNAs. Understanding the regulation of 10 sgRNAs is a conceptual challenge. In analyzing commonalities of a replicase complex in producing so many …

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Use Of A 3 Cytoplasm To Reduce Risk Of Gene Flow Through Sorghum Pollen, Jeffrey F. Pedersen, D. B. Marx, Deanna L. Funnell

Department of Plant Pathology: Faculty Publications

A critical impediment to field testing and deployment of transgenic sorghum [Sorghum bicolor (L.) Moench] is the threat of gene flow to weedy relatives through pollen. A technique using sorghum with A₃ cytoplasmic male sterility to control transgene flow through pollen while using nontransgenic pollinators is described and an experiment was designed to evaluate the risk of viable pollen flow using A₃ hybrids under field conditions. Seed set under pollinating bags (an indicator of fertile pollen) was evaluated at the University of Nebraska Field Laboratory at Ithaca, NE, in 2001 and 2002 on selfed F₂ progeny …

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Bcl-2 Family Members Inhibit Oxidative Stress-Induced Programmed Cell Death In Saccharomyces Cerevisiae, Shao-Rong Chen, David Dunigan, Martin Dickman

Department of Plant Pathology: Faculty Publications

Selected antiapoptotic genes were expressed in baker’s yeast (Saccharomyces cerevisiae) to evaluate cytoprotective effects during oxidative stress. When exposed to treatments resulting in the generation of reactive oxygen species (ROS), including H₂O₂, menadione, or heat shock, wild-type yeast died and exhibited apoptotic-like characteristics, consistent with previous studies. Yeast strains were generated expressing nematode ced-9, human bcl-2, or chicken bcl-xl genes. These transformants tolerated a range of oxidative stresses, did not display features associated with apoptosis, and remained viable under conditions that were lethal to wildtype yeast. Yeast strains expressing a mutant antiapoptotic gene (bcl-2 …

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Induced Resistance As A Mechanism Of Biological Control By Lysobacter Enzymogenes Strain C3, Ozlem Kilic-Ekici, Gary Y. Yuen

Department of Plant Pathology: Faculty Publications

Induced resistance was found to be a mechanism for biological control of leaf spot, caused by Bipolaris sorokiniana, in tall fescue (Festuca arundinacea) using the bacterium Lysobacter enzymogenes strain C3. Resistance elicited by C3 suppressed germination of B. sorokiniana conidia on the phylloplane in addition to reducing the severity of leaf spot. The pathogen-inhibitory effect could be separated from antibiosis by using heat-inactivated cells of C3 that retained no antifungal activity. Application of live or heat-killed cells to tall fescue leaves resulted only in localized resistance confined to the treated leaf, whereas treatment of roots resulted in …

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Evolution Of Wheat Streak Mosaic Virus: Dynamics Of Population Growth Within Plants May Explain Limited Variation, Roy C. French, Drake C. Stenger

Department of Plant Pathology: Faculty Publications

Like many other plant RNA viruses, Wheat streak mosaic virus (WSMV) sequence diversity within and among infected plants is low given the large number of virions produced. This may be explained by considering aspects of plant virus life history. Intracellular replication of RNA viruses is predominately linear, not exponential, which means that the rate at which mutations accumulate also is linear. Bottlenecks during systemic movement further limit diversity. Analysis of mixed infections with two WSMV isolates suggests that about four viral genomes participate in systemic invasion of each tiller. Low effective population size increases the role of stochastic processes on …

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Review Of Molecular Biology Of Fungal Development, Mycology Series, Volume 15, Marty Dickman

Department of Plant Pathology: Faculty Publications

Numerous publications, books, and textbooks are available that treat the subject of developmental biology. Far less is available detailing the fungi, an important group of organisms that have implications in a broad variety of contexts from medical to agricultural to food, and of course as model systems for “higher” eukaryotes. This nicely edited book by Osiewacz is an attempt to fill that gap. He has compiled an impressive list of authors, who represent leaders in their respective fields. This gives readers a detailed and current view of a broad array of fungal processes and lifestyles, ranging from saprophytes to pathogens …

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Evaluation Of Resistance Screening Methods For Sclerotinia Stem Rot Of Soybean And Dry Bean, Linda S. Kull, Tri D. Vuong, Kris S. Powers, Kent M. Eskridge, James R. Steadman, Glen L. Hartman

Department of Plant Pathology: Faculty Publications

Three methods to identify levels of resistance to Sclerotinia sclerotiorum in soybean (Glycine max) and dry bean (Phaseolus vulgaris) were compared using multiple data analyses. The three methods were mycelial plug inoculations of cotyledons, cut stems, and detached leaves. Six S. sclerotiorum isolates of known relative aggressiveness were inoculated on each of three soybean and dry bean cultivars with varied response to S. sclerotiorum. For soybean, all three inoculation methods accurately identified isolate aggressiveness irrespective of cultivar, but identification of susceptible and partially resistant soybean cultivars was influenced by isolate. For dry bean, the cotyledon and cut …

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Fungal Biology And Agriculture: Revisiting The Field, O. Yarden, D. J. Ebbole, S. Freeman, R. J. Rodriguez, M. B. Dickman

Department of Plant Pathology: Faculty Publications

Plant pathology has made significant progress over the years, a process that involved overcoming a variety of conceptual and technological hurdles. Descriptive mycology and the advent of chemical plant-disease management have been followed by biochemical and physiological studies of fungi and their hosts. The later establishment of biochemical genetics along with the introduction of DNA-mediated transformation have set the stage for dissection of gene function and advances in our understanding of fungal cell biology and plant–fungus interactions. Currently, with the advent of high-throughput technologies, we have the capacity to acquire vast data sets that have direct relevance to the numerous …

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Unusual Life Style Of Giant Chlorella Viruses, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Paramecium bursaria chlorella virus (PBCV-1) is the prototype of a family of large, icosahedral, plaque-forming, dsDNA viruses that replicate in certain unicellular, eukaryotic chlorella-like green algae. Its 330-kb genome contains ~373 protein-encoding genes and 11 tRNA genes. The predicted gene products of ~50% of these genes resemble proteins of known function, including many that are unexpected for a virus, e.g., ornithine decarboxylase, hyaluronan synthase, GDP-D-mannose 4,6 dehydratase, and a potassium ion channel protein. In addition to their large genome size, the chlorella viruses have other features that distinguish them from most viruses. These features include: (a) The viruses encode multiple …

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Are Chlorella Viruses A Rich Source Of Ion Channel Genes?, Ming Kang, Anna Moroni, Sabrina Gazzarrini, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Plaque-forming dsDNA (>330 kb) viruses that infect certain unicellular, eukaryotic chlorella-like green algae contain ~375 protein-encoding genes. These proteins include a 94 amino acid K+ channel protein, called Kcv, as well as two putative ligand-gated ion channels. The viruses also encode other proteins that could be involved in the assembly and/ or function of ion channels, including protein kinases and a phosphatase, polyamine biosynthetic enzymes and histamine decarboxylase.

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Transcription Strategy In A Closterovirus: A Novel 5'-Proximal Controller Element Of Citrus Tristeza Virus Produces 5'- And 3'-Terminal Subgenomic Rnas And Differs From 3' Open Reading Frame Controller Elements, Siddarame Gowda, Maria A. Ayllon, Satyanarayana Tatineni, Moshe Bar-Joseph, William O. Dawson

Department of Plant Pathology: Faculty Publications

Citrus tristeza virus (CTV) produces more than thirty 3'- or 5'-terminal subgenomic RNAs (sgRNAs) that accumulate to various extents during replication in protoplasts and plants. Among the most unusual species are two abundant populations of small 5'-terminal sgRNAs of approximately 800 nucleotides (nt) termed low-molecular-weight tristeza (LMT1 and LMT2) RNAs. Remarkably, CTV replicons with all 10 3' genes deleted produce only the larger LMT1 RNAs. These 5'-terminal positive-sense sgRNAs do not have corresponding negative strands and were hypothesized to be produced by premature termination during plus-strand genomic RNA synthesis. We characterized a cis-acting element that controls the production …

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A Protein Kinase From Colletotrichum Trifolii Is Induced By Plant Cutin And Is Required For Appressorium Formation, M. B. Dickman, Y.-S. Ha, Z. Yang, B. J. Adams, C. Huang

Department of Plant Pathology: Faculty Publications

When certain phytopathogenic fungi contact plant surfaces, specialized infection structures (appressoria) are produced that facilitate penetration of the plant external barrier; the cuticle. Recognition of this hydrophobic host surface must be sensed by the fungus, initiating the appropriate signaling pathway or pathways for pathogenic development. Using polymerase chain reaction and primers designed from mammalian protein kinase C sequences (PKC), we have isolated, cloned, and characterized a protein kinase from Colletotrichum trifolii, causal agent of alfalfa anthracnose. Though sequence analysis indicated conserved sequences in mammalian PKC genes, we were unable to induce activity of the fungal protein using known activators …

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Department of Plant Pathology: Faculty Publications

Department of Plant Pathology: Faculty Publications

Effects Of Modification Of The Transcription Initiation Site Context On Citrus Tristeza Virus Subgenomic Rna Synthesis, Maria A. Ayllon, Siddarame Gowda, Satyanarayana Tatineni, Alexander V. Karasev, Scott Adkins, Munir Mawassi, Jose Guerri, Pedro Moreno, William O. Dawson

Department of Plant Pathology: Faculty Publications

Use Of A 3 Cytoplasm To Reduce Risk Of Gene Flow Through Sorghum Pollen, Jeffrey F. Pedersen, D. B. Marx, Deanna L. Funnell

Department of Plant Pathology: Faculty Publications

Bcl-2 Family Members Inhibit Oxidative Stress-Induced Programmed Cell Death In Saccharomyces Cerevisiae, Shao-Rong Chen, David Dunigan, Martin Dickman

Department of Plant Pathology: Faculty Publications

Induced Resistance As A Mechanism Of Biological Control By Lysobacter Enzymogenes Strain C3, Ozlem Kilic-Ekici, Gary Y. Yuen

Department of Plant Pathology: Faculty Publications

Evolution Of Wheat Streak Mosaic Virus: Dynamics Of Population Growth Within Plants May Explain Limited Variation, Roy C. French, Drake C. Stenger

Department of Plant Pathology: Faculty Publications

Review Of Molecular Biology Of Fungal Development, Mycology Series, Volume 15, Marty Dickman

Department of Plant Pathology: Faculty Publications

Evaluation Of Resistance Screening Methods For Sclerotinia Stem Rot Of Soybean And Dry Bean, Linda S. Kull, Tri D. Vuong, Kris S. Powers, Kent M. Eskridge, James R. Steadman, Glen L. Hartman

Department of Plant Pathology: Faculty Publications

Fungal Biology And Agriculture: Revisiting The Field, O. Yarden, D. J. Ebbole, S. Freeman, R. J. Rodriguez, M. B. Dickman

Department of Plant Pathology: Faculty Publications

Unusual Life Style Of Giant Chlorella Viruses, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Are Chlorella Viruses A Rich Source Of Ion Channel Genes?, Ming Kang, Anna Moroni, Sabrina Gazzarrini, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Department of Plant Pathology: Faculty Publications

A Protein Kinase From Colletotrichum Trifolii Is Induced By Plant Cutin And Is Required For Appressorium Formation, M. B. Dickman, Y.-S. Ha, Z. Yang, B. J. Adams, C. Huang

Department of Plant Pathology: Faculty Publications