Digital Commons Network^™

First Report Of Leaf Spot Of Smooth Bromegrass Caused By Pithomyces Chartarum In Nebraska, C. Eken, C. C. Jochum, G. Y. Yuen

Department of Plant Pathology: Faculty Publications

Smooth bromegrass (Bromus inermis Leyss.) is the most common perennial grass species cultivated for forage in North America. During late fall of 2004, smooth bromegrass plants in Lincoln, NE were observed to have brown lesions on leaf midveins that were several centimeters long. Symptomatic leaves were surface disinfested for 1 min in 2% NaOCl and incubated at 25°C on potato dextrose agar (PDA) and water agar. The fungus, Pithomyces chartarum (Berk. & Curt) Ellis, was isolated consistently and identified on the basis of morphological characteristics (1). Colonies were effused and black on PDA. Conidiophores measured 3.5 to 8 …

Bioinformatics-Enabled Identification Of The Hrpl Regulon And Type Iii Secretion System Effector Proteins Of Pseudomonas Syringae Pv. Phaseolicola 1448a, Monica Vencato, Fang Tian, James R. Alfano, C. Robin Buell, Samuel Cartinhour, Genevieve A. Declerck, David S. Guttman, John Stavrinides, Vinita Joardar, Magdalen Lindeberg, Philip A. Bronstein, John W. Mansfield, Christopher R. Myers, Alan Collmer, David J. Schneider

Department of Plant Pathology: Faculty Publications

The ability of Pseudomonas syringae pv. phaseolicola to cause halo blight of bean is dependent on its ability to translocate effector proteins into host cells via the hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS). To identify genes encoding type III effectors and other potential virulence factors that are regulated by the HrpL alternative sigma factor, we used a hidden Markov model, weight matrix model, and type III targeting-associated patterns to search the genome of P. syringae pv. phaseolicola 1448A, which recently was sequenced to completion. We identified 44 high-probability putative Hrp promoters upstream of genes encoding the …

Regulation Of Hyphal Morphogenesis And The Dna Damage Response By The Aspergillus Nidulans Atm Homolog Atma, Iran Malavazi, Camile P. Semighini, Marcia Regina Von Zeska Kress, Steven D. Harris, Gustavo H. Goldman

Department of Plant Pathology: Faculty Publications

Ataxia telangiectasia (A-T) is an inherited disorder characterized by progressive loss of motor function and susceptibility to cancer. The most prominent clinical feature observed in A-T patients is the degeneration of Purkinje motor neurons. Numerous studies have emphasized the role of the affected gene product, ATM, in the regulation of the DNA damage response. However, in Purkinje cells, the bulk of ATM localizes to the cytoplasm and may play a role in vesicle trafficking. The nature of this function, and its involvement in the pathology underlying A-T, remain unknown. Here we characterize the homolog of ATM (AtmA) in the filamentous …

Seagrass–Pathogen Interactions: ‘Pseudo-Induction’ Of Turtlegrass Phenolics Near Wasting Disease Lesions, Latina Steele, Melanie Caldwell, Anne Boettcher, Tom Arnold

Biology Faculty Publications

Marine protists of the genus Labyrinthula cause the seagrass wasting disease, which is associated with regional die-offs of eelgrass Zostera marina and also infects turtlegrass Thalassia testudinum . The ability of seagrasses to resist pathogen attack is determined by multiple factors, which are poorly understood. One factor hypothesized to influence seagrass disease resistance is the presence of (poly)phenolic natural products such as caffeic acid, which inhibits the growth of L. zosterae in in vitro laboratory bioassays. This hypothesis has been supported by reports of pathogen-induced phenolic accumulations in eelgrass Z. marina. To test the response of T. testudinum to …

Complete Deletion Of Wheat Streak Mosaic Virus Hc-Pro: A Null Mutant Is Viable For Systemic Infection, Drake C. Stenger, Roy C. French, Frederick E. Gildow

Department of Plant Pathology: Faculty Publications

A Wheat streak mosaic virus (WSMV) genome lacking HC-Pro was constructed and confirmed by reverse transcription-PCR to systemically infect wheat, oat, and corn. Coupled in vitro transcription/translation reactions indicated that WSMV P1 proteinase cleaved the polyprotein at the P1/P3 junction of the HC-Pro null mutant. The WSMV HC-Pro null mutant was competent for virion formation, but the virus titer was reduced 4.5-fold relative to that of the wild type. Collectively, these results indicate that WSMV HC-Pro is dispensable for replication and movement, two essential processes that are disrupted by point and small-insertion mutations introduced into potyvirus HC-Pro.

First Report Of Crown And Stem Rot Of Orchid (Orchis Palustris) Caused By Sclerotinia Minor, C. Eken, S. Ercişli, A. Eşitken, E. Demirci, G. Y. Yuen

Department of Plant Pathology: Faculty Publications

Orchis palustris Jacq. is a wild orchid native to wetlands in eastern Anatolia. During June of 2003, near Erzurum, Turkey, a decline of this orchid was observed in several meadows that had been irrigated for forage production. Stems were chlorotic, wilted, and collapsed. There was a soft, watery rot at the crowns and lower stems. White mycelium and black sclerotia formed on necrotic stem and crown tissues. The fungus was isolated from sclerotia on potato dextrose agar (PDA) and identified as Sclerotinia minor Jagger on the basis of small sclerotia (0.5 to 2.5 mm long) scattered throughout the colonies (2). …

Plant Virus Hc-Pro Is A Determinant Of Eriophyid Mite Transmission, Drake C. Stenger, Gary L. Hein, Frederick E. Gildow, Kempton M. Horken, Roy C. French

Department of Plant Pathology: Faculty Publications

The eriophyid mite transmitted Wheat streak mosaic virus (WSMV; genus Tritimovirus, family Potyviridae) shares a common genome organization with aphid transmitted species of the genus Potyvirus. Although both tritimoviruses and potyviruses encode helper component-proteinase (HC-Pro) homologues (required for nonpersistent aphid transmission of potyviruses), sequence conservation is low (amino acid identity, ~16%), and a role for HC-Pro in semipersistent transmission of WSMV by the wheat curl mite (Aceria tosichella [Keifer]) has not been investigated. Wheat curl mite transmissibility was abolished by replacement of WSMV HC-Pro with homologues of an aphid transmitted potyvirus (Turnip mosaic virus), …

Pseudomonas Syringae Type Iii Chaperones Shco1, Shcs1, And Shcs2 Facilitate Translocation Of Their Cognate Effectors And Can Substitute For Each Other In The Secretion Of Hopo1-1, Ming Guo, Scott T. Chancey, Fang Tian, Zhengxiang Ge, Yashitola Jamir, James R. Alfano

Center for Plant Science Innovation: Faculty Publications

The Pseudomonas syringae type III secretion system (TTSS) translocates effector proteins into plant cells. Several P. syringae effectors require accessory proteins called type III chaperones (TTCs) to be secreted via the TTSS. We characterized the hopO1-1, hopS1, and hopS2 operons in P. syringae pv. tomato DC3000; these operons encode three homologous TTCs, ShcO1, ShcS1, and ShcS2. ShcO1, ShcS1, and ShcS2 facilitated the type III secretion and/or translocation of their cognate effectors HopO1-1, HopS1, and HopS2, respectively. ShcO1 and HopO1-1 interacted with each other in yeast two-hybrid and coimmunoprecipitation assays. Interestingly, ShcS1 and ShcS2 were capable of substituting for …

Mutagenesis Of Β-1,3-Glucanase Genes In Lysobacter Enzymogenes Strain C3 Results In Reduced Biological Control Activity Toward Bipolaris Leaf Spot Of Tall Fescue And Pythium Damping-Off Of Sugar Beet, Jeffrey D. Palumbo, Gary Y. Yuen, C. Christine Jochum, Kristin Tatum, Donald Y. Kobayashi

Department of Plant Pathology: Faculty Publications

Lysobacter enzymogenes produces extracellular lytic enzymes capable of degrading the cell walls of fungi and oomycetes. Many of these enzymes, including β-1,3-glucanases, are thought to contribute to the biological control activity expressed by several strains of the species. L. enzymogenes strain C3 produces multiple extracellular β-1,3-glucanases encoded by the gluA, gluB, and gluC genes. Analysis of the genes indicates they are homologous to previously characterized genes in the related strain N4-7, each sharing >95% amino acid sequence identity to their respective counterparts. The gluA and gluC gene products encode enzymes belonging to family 16 glycosyl …

Green Fluorescent Protein Is Lighting Up Fungal Biology, J.M. Lorang, R.P. Tuori, J.P. Martinez, T.L. Sawyer, R.S. Redman, J.A. Rollins, T. J. Wolpert, K.B. Johnson, R. J. Rodriguez, M. B. Dickman, L. M. Ciuffetti

Department of Plant Pathology: Faculty Publications

Prasher (42) cloned a cDNA for the green fluorescent protein (GFP) gene from the jellyfish Aequorea victoria in 1992. Shortly thereafter, to the amazement of many investigators, this gene or derivatives thereof were successfully expressed and conferred fluorescence to bacteria and Caenorhabditis elegans cells in culture (10, 31), followed by yeast (24, 39), mammals (40), Drosophila (66), Dictyostelium (23, 30), plants (28, 49), and filamentous fungi (54). The tremendous success of GFP as a reporter can be attributed to unique qualities of this 238- amino-acid, 27-kDa protein which absorbs light at maxima of 395 and 475 nm and emits light …

'Paclims': A Component Lim System For High-Throughput Functional Genomic Analysis, Nicole Donofrio, Ravi Rajagopalon, Douglas Brown, Stephen Diener, Donald Windham, Shelly Nolin, Anna Floyd, Thomas Mitchell, Natalia Galadima, Sara Tucker, Marc J. Orbach, Gayatri Patel, Mark Farman, Vishal Pampanwar, Cari Soderlund, Yong-Hwan Lee, Ralph A. Dean

Plant Pathology Faculty Publications

BACKGROUND: Recent advances in sequencing techniques leading to cost reduction have resulted in the generation of a growing number of sequenced eukaryotic genomes. Computational tools greatly assist in defining open reading frames and assigning tentative annotations. However, gene functions cannot be asserted without biological support through, among other things, mutational analysis. In taking a genome-wide approach to functionally annotate an entire organism, in this application the approximately 11,000 predicted genes in the rice blast fungus (Magnaporthe grisea), an effective platform for tracking and storing both the biological materials created and the data produced across several participating institutions was required.

RESULTS: …

Proposed Guidelines For A Unified Nomenclature And Phylogenetic Analysis Of Type Iii Hop Effector Proteins In The Plant Pathogen Pseudomonas Syringae, Magdalen Lindeberg, John Stavrinides, Jeffrey H. Chang, James R. Alfano, Alan Collmer, Jeffrey L. Dangl, Jean T. Greenberg, John W. Mansfield, David S. Guttman

Department of Plant Pathology: Faculty Publications

Pathovars of Pseudomonas syringae interact with their plant hosts via the action of Hrp outer protein (Hop) effector proteins, injected into plant cells by the type III secretion system (TTSS). Recent availability of complete genome sequences for a number of P. syringae pathovars has led to a significant increase in the rate of effector discovery. However, lack of a systematic nomenclature has resulted in multiple names being assigned to the same Hop, unrelated Hops designated by the same alphabetic character, and failure of name choices to reflect consistent standards of experimental confirmation or phylogenetic relatedness. Therefore, specific experimental and bioinformatic …

Crop Updates 2005 - Cereals, Darshan Sharma, Brenda Shackley, Mohammad Amjad, Christine M. Zaicou-Kunesch, Wal Anderson, D. Tennant, Steve Penny Jr, Ben Curtis, Veronika Reck, Richard Richards, Gavin Knell, Steve Curtin, David Sermon, Alan Bedggood, T. B. Biddulph, T. L. Setter, J. A. Plummer, D. J. Mares, H. Khabaz-Saberi, I. Waters, G. Mcdonald, Harmohinder Dhammu, David Nicholson, Chris Roberts, Stephen Loss, Ross Brennan, Kithsiri Jayasena, Eddy Pol, Simon Teakle, Rob Loughman, Ciara Beard, Blakely Paynter, K. Tanaka, G. Poulish, A. Smith, Paul Damon, Zed Rengel, Lionel Martin, Narelle Hill, Ron Mctaggart, Ray Tugwell, Geoff J. Thomas, Manisha Shankar, John Majewski, D. Foster, H. Golzar, J. Piotrowski, Rob Grima, Jeff Russell, Angie Roe, Vivien A. Vanstone, Sean Kelly, Helen Hunter, Mena C. Gilchrist, C. R. Newman, Svetlana Micic, Phil Michael, Gabrielle Coupland, Ern Kostas, Mohammed Hamza, Tina Botwright Acuña, Len Wade, Ingrid Richardson

Crop Updates

This session covers thirty six papers from different authors:

WHEAT AGRONOMY

1. Optimum sowing time of new wheat varieties in Western Australia, Darshan Sharma, Brenda Shackley, Mohammad Amjad, Christine M. Zaicou-Kunesch and Wal Anderson, Department of Agriculture

2. Wheat varieties updated in ‘Flowering Calculator’: A model predicting flowering time, B. Shackley, D. Tennant, D. Sharma and C.M. Zaicou-Kunesch, Department of Agriculture

3. Plant populations for wheat varieties, Christine M. Zaicou-Kunesch, Wal Anderson, Darshan Sharma, Brenda Shackley and Mohammad Amjad, Department of Agriculture

4. New wheat cultivars response to fertiliser nitrogen in four major agricultural regions of Western Australia, Mohammad Amjad, …

Crop Updates 2005 - Farming Systems, David Stephens, Nicola Telcik, Ross Kingwell, Wayne Pluske, Bill Bowden, Mike Collins, Frances Hoyle, D. V. Murphy, N. Milton, M. Osman, L. K. Abbott, W. R. Cookson, S. Darmawanto, Bill Crabtree, Geoff Anderson, Darren Kidson, Ross Brennan, Nick Drew, Craig Scanlan, Lisa Sherriff, Bob French, Reg Lunt, Jeff Russell, Angie Roe, Ian Maling, Matthew Adams, George Yan, Mohammad Hamza, Glen Riethmuller, Wal Anderson, Angela Loi, Phil Nichols, Clinton Revell, David Ferris, Phil Ward, Andrea Hills, Sally-Anne Penny, David Hall, Michael Robertson, Don Gaydon, Tress Walmsley, Caroline Peek, Megan Abrahams, Paul Raper, Richard O'Donnell, Trevor Lacey, Meredith Fairbanks, David Tennant, Cameron Weeks, Richard Quinlan, Alexandra Edward, Chris Carter, Doug Hamilton, Peter Tozer, Renaye Horne, Tracey Gianatti, Paul Carmody, Ian Foster, Michele John, Ross George, Imma Farré, Ian Kininmonth, Dennis Van Gool, Neil Coles, Bill Porter, Louise Barton, Richard Harper, Peter Ritson, Tony Beck, Chris Mitchell, Michael Hill, Fiona Barker-Reid, Will Gates, Ken Wilson, Rob Baigent, Ian Galbally, Mick Meyer, Ian Weeks, Traci Griffin, D. Rodriguez, M. Probust, M. Meyers, D. Chen, A. Bennett, W. Strong, R. Nussey, I Galbally, M. Howden

Crop Updates

This session covers forty four papers from different authors:

PLENARY

1. 2005 Outlook, David Stephens and Nicola Telcik, Department of Agriculture

FERTILITY AND NUTRITION

2. The effect of higher nitrogen fertiliser prices on rotation and fertiliser strategies in cropping systems, Ross Kingwell, Department of Agriculture and University of Western Australia

3. Stubble management: The short and long term implications for crop nutrition and soil fertility, Wayne Pluske, Nutrient Management Systems and Bill Bowden, Department of Agriculture

4. Stubble management: The pros and cons of different methods, Bill Bowden, Department of Agriculture, Western Australia and Mike Collins, …

Polarisome Meets Spitzenkö̈Rper: Microscopy, Genetics, And Genomics Converge, Steven D. Harris, Nick D. Read, Robert W. Roberson, Brian Shaw, Stephan Seiler, Mike Plamann, Michelle Momany

Department of Plant Pathology: Faculty Publications

The impact of filamentous fungi on human welfare has never been greater. Fungi are acknowledged as the most economically devastating plant pathogens (1) and are attaining increasing notoriety for their ability to cause life-threatening infections in humans (57, 71), and fungal products sustain a billion dollar manufacturing industry (70). The tools available to study filamentous fungi are more sophisticated than ever and include the complete annotated genome sequences of multiple filamentous fungi (12), resources being made available through various functional genomics projects, and advanced bioimaging methods, including high-resolution live-cell imaging (20, 32) and electron tomography (19, 50). The increasing impact …

Mutual Interference Between Genomic Rna Replication And Subgenomic Mrna Transcription In Brome Mosaic Virus, Valery Z. Grdzelishvili, Hernan Garcia-Ruiz, Tokiko Watanabe, Paul Ahlquist

Department of Plant Pathology: Faculty Publications

Replication by many positive-strand RNA viruses includes genomic RNA amplification and subgenomic mRNA (sgRNA) transcription. For brome mosaic virus (BMV), both processes occur in virus-induced, membrane- associated compartments, require BMV replication factors 1a and 2a, and use negative-strand RNA3 as a template for genomic RNA3 and sgRNA syntheses. To begin elucidating their relations, we examined the interaction of RNA3 replication and sgRNA transcription in Saccharomyces cerevisiae expressing 1a and 2a, which support the full RNA3 replication cycle. Blocking sgRNA transcription stimulated RNA3 replication by up to 350%, implying that sgRNA transcription inhibits RNA3 replication. Such inhibition was independent of the …

The Glycosphingolipid Globotriaosylceramide In The Metastatic Transformation Of Colon Cancer, Olga Kovbasnjuk, Rakhilya Mourtazina, Boris Baibakov, Thomas Wang, Christian Elowsky, Michael A. Choti, Anne Kane, Mark Donowitz

Department of Plant Pathology: Faculty Publications

The most devastating aspect of cancer is the emergence of metastases. Thus, identification of potentially metastatic cells among a tumor cell population and the underlying molecular changes that switch cells to a metastatic state are among the most important issues in cancer biology. Here we show that, although normal human colonic epithelial cells lack the glycosphingolipid globotriaosylceramide (Gb₃), this molecule is highly expressed in metastatic colon cancer. In addition, a subpopulation of cells that are greatly enriched in Gb₃ and have an invasive phenotype was identified in human colon cancer cell lines. In epithelial cells in culture, …

The Hrpk Operon Of Pseudomonas Syringae Pv. Tomato Dc3000 Encodes Two Proteins Secreted By The Type Iii (Hrp) Protein Secretion System: Hopb1 And Hrpk, A Putative Type Iii Translocator, Tanja Petnicki-Ocwieja, Karin V. Van Dijk, James R. Alfano

Center for Plant Science Innovation: Faculty Publications

Pseudomonas syringae is a gram-negative bacterial plant pathogen that is dependent on a type III protein secretion system (TTSS) and the effector proteins it translocates into plant cells for pathogenicity. The P. syringae TTSS is encoded by hrp-hrc genes that reside in a central region of a pathogenicity island (Pai). Flanking one side of this Pai is the exchangeable effector locus (EEL). We characterized the transcriptional expression of the open reading frames (ORFs) within the EEL of P. syringae pv. tomato DC3000. One of these ORFs, PSPTO1406 (hopB1) is expressed in the same transcriptional unit as hrpK. …

The Structure Of A T=169d Algal Virus, Pbcv-1, At 15Å Resolution, X. Yan, V. Bowman, N. H. Olson, James Gurnon, James L. Van Etten, Michael G. Rossmann, T. S. Baker

James Van Etten Publications

Paramecium bursaria chlorella virus 1 (PBCV-1) (genus Chlorovirus, family Phycodnaviridae), infects certain unicellular, exsymbiotic, chlorella-like green algae [1]. The PBCV-1 virion (~1x109 Da) has a linear dsDNA genome (330kbp) and contains at least 100 different proteins [1, unpublished data]. A published cryo-electron microscopy and three-dimensional (3D) image reconstruction of PBCV-1 (26Å resolution) revealed that the outer icosahedral glycoprotein capsid, with a maximum diameter of 1,900Å along the five-fold axis, consists of 1680 trimeric capsomers (trimer) and 12 pentameric capsomers (pentamer) [2]. These capsomers are arranged on a T=169d (h=7, k=8) quasi-equivalent lattice. The trimers and pentamers are organized into 20 …

Functional Implication Of The Trna Genes Encoded In The Chlorella Virus Pbcv-L Genome, Da Young Lee, Michael V. Graves, James L. Van Etten, Tae-Jin Choi

James Van Etten Publications

The prototype Chlorella virus PBCV-l encodes 11 tRNA genes and over 350 protein-encoding genes in its 330 kbp genome. Initial attempts to overexpress the recombinant A189/192R protein, a putative virus attachment protein, in E. coli strain BL21(DE3) SI were unsuccessful, and multiple protein bands were detected on Western blots. However, the full-length A189/192R recombinant protein or fragments derived from it were detected when they were expressed in E. coli BL21 CodonPlus (DE3) RIL, which contains extra tRNAs. Codon usage analysis of the a1891192r gene showed highly biased usage of the AGA and AUA codons compared to genes encoded by E. …

Incorporating Molecular Identification Of Meloidogyne Spp. Into A Large-Scale Regional Nematode Survey, Thomas O. Powers, P. G. Mullin, T. S. Harris, L. A. Sutton, R. S. Higgins

Department of Plant Pathology: Faculty Publications

A regional nematode survey of potato fields was conducted in the central United States during 2002 and 2003. The survey encompassed seven states and included a morphological and molecular examination of nematodes of regulatory concern from 1,929 soil samples. No regulated pest species were recovered during this survey. Meloidogyne juveniles extracted from soil were identified by mitochondrial and 18S ribosomal molecular markers. Eighty-two DNA sequences representing the two marker regions for Meloidogyne species were submitted to GenBank to facilitate evaluation of marker variability. Sufficient 18S variation was observed among some Meloidogyne species to aid in identification; however, nucleotide sequence from …

Morphogenesis In Germinating Fusarium Graminearum Macroconidia, Steven D. Harris

Department of Plant Pathology: Faculty Publications

Fusarium graminearum (teleomorph Gibberella zeae) is a significant pathogen of wheat and corn. F. graminearum forms multicellular macroconidia that play an important role in dissemination of the disease. The spatial pattern of morphogenesis in germinating macroconidia is described. Germ tubes preferentially emerge from the apical cells in a bipolar pattern that appears to be common to filamentous fungi. Chitin deposition occurs at two locations: the spore apices and cortical regions of macroconidial cells that subsequently produce a germ tube. The spatial pattern of morphogenesis requires the presence of functional microtubules, which may be responsible for the transport of key …

Chlorovirus: A Genus Of Phycodnaviridae That Infects Certain Chlorella-Like Green Algae, Ming Kang, David Dunigan, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Taxonomy: Chlorella viruses are assigned to the family Phycodnaviridae, genus Chlorovirus, and are divided into three species: Chlorella NC64A viruses, Chlorella Pbi viruses and Hydra viridis Chlorella viruses. Chlorella viruses are large, icosahedral, plaque-forming, dsDNA viruses that infect certain unicellular, chlorella-like green algae. The type member is Paramecium bursaria chlorella virus 1 (PBCV-1).

Physical properties: Chlorella virus particles are large (molecular weight ~1 × 10⁹ Da) and complex. The virion of PBCV-1 contains more than 100 different proteins; the major capsid protein, Vp54, comprises ~40% of the virus protein. Cryoelectron microscopy and three-dimensional image reconstruction of PBCV-1 virions …

Proline Suppresses Apoptosis In The Fungal Pathogen Colletotrichum Trifolii, Changbin Chen, Martin B. Dickman

Department of Plant Pathology: Faculty Publications

The role of reactive oxygen species (ROS) in cell communication, control of gene expression, and oxygen sensing is well established. Inappropriate regulation of ROS levels can damage cells, resulting in a diseased state. In Colletotrichum trifolii, a fungal pathogen of alfalfa, the mutationally activated oncogenic fungal Ras (DARas) elevates levels of ROS, causing abnormal fungal growth and development and eventual apoptotic-like cell death but only when grown under nutrient-limiting conditions. Remarkably, restoration to the wild-type phenotype requires only proline. Here, we describe a generally unrecognized function of proline: its ability to function as a potent antioxidant and inhibitor of …

Chlorella Virus Marburg Topoisomerase Ii: High Dna Cleavage Activity As A Characteristic Of Chlorella Virus Type Ii Enzymes, Jennifer S. Dickey, Tae-Jin Choi, James L. Van Etten, Neil Osheroff

Department of Plant Pathology: Faculty Publications

Although the formation of a covalent enzyme-cleaved DNA complex is a prerequisite for the essential functions of topoisomerase II, this reaction intermediate has the potential to destabilize the genome. Consequently, all known eukaryotic type II enzymes maintain this complex at a low steady-state level. Recently, however, a novel topoisomerase II was discovered in Paramecium bursaria chlorella virus-1 (PBCV-1) that has an exceptionally high DNA cleavage activity [Fortune et al. (2001) J. Biol. Chem. 276, 24401-24408]. If robust DNA cleavage is critical to the physiological functions of chlorella virus topoisomerase II, then this remarkable characteristic should be …

Fundamental Contribution Of Β-Oxidation To Polyketide Mycotoxin Production In Planta, Lori A. Maggio-Hall, Richard A. Wilson, Nancy P. Keller

Fungal Molecular Plant-Microbe Interactions

Seed contamination with polyketide mycotoxins, including aflatoxin (AF) and sterigmatocystin (ST) produced by Aspergillus spp., is an agricultural, economic, and medical issue worldwide. Acetyl-CoA, the fundamental building block of all known fungal polyketides, is generated by a large number of biochemical pathways, including β-oxidation of fatty acids and glycolysis of sugars. We present several lines of evidence to support a major role for seed fatty acids in formation of AF and ST in A. flavus, A. parasiticus, and A. nidulans. Aspergillus strains exhibiting canonical signs of oleic acid–induced peroxisome proliferation, including increased catalase activity, β-oxidation gene expression, and …

Genome Sequences Of Agropyron Mosaic Virus And Hordeum Mosaic Virus Support Reciprocal Monophyly Of The Genera Potyvirus And Rymovirus In The Family Potyviridae, Roy C. French, D.C. Stenger

Department of Plant Pathology: Faculty Publications

Assignment of mite-transmitted species to the genus Rymovirus (family Potyviridae) has changed several times, and the status of the genus has been questioned. To address this issue, complete genome sequences of the rymoviruses Agropyron mosaic virus (AgMV) and Hordeum mosaic virus (HoMV) were determined. AgMV (9540 nucleotides) and HoMV (9463 nucleotides) each encode a single polyprotein with proteinase cleavage sites demarcating protein products characteristic of monopartite species of the family Potyviridae. Of the described species of Potyviridae, AgMV and HoMV are most closely related to each other (68.5% nucleotide and 71.6% amino acid sequence identity) and equidistant …

Expression Of The Tobacco Β- 1,3-Glucanase Gene, Pr-2d, Following Induction Of Sar With Peronospora Tabacina, Deanna L. Funnell, Christopher B. Lawrence, Jeffrey F. Pedersen, Christopher L. Schardl

Department of Plant Pathology: Faculty Publications

Systemic acquired resistance (SAR) is induced following inoculation of Peronospora tabacina sporangia into the stems of Nicotiana tabacum plants highly susceptible to the pathogen. Previous results have shown that accumulation of acidic P-1,3-glucanases (PR-2's) following induction of SAR by P. tabacina may contribute to resistance to P. tabacina. We showed that up-regulation of the PR-2 gene, PR-2d, following stem inoculation with P. tabacina, is associated with SAR. Studies using plants transformed with GUS constructs containing the full length promoter from PR-2d or promoter deletions, provided evidence that a previously characterized regulatory element that is involved in response to …

Disabling Surveillance: Bacterial Type Iii Secretion System Effectors That Suppress Innate Immunity, Avelina Espinosa, James R. Alfano

Center for Plant Science Innovation: Faculty Publications

Many Gram-negative bacterial pathogens of plants and animals are dependent on a type III protein secretion system (TTSS). TTSSs translocate effector proteins into host cells and are capable of modifying signal transduction pathways. The innate immune system of eukaryotes detects the presence of pathogens using specific pathogen recognition receptors (PRRs). Plant PRRs include the FLS2 receptor kinase and resistance proteins. Animal PRRs include Tolllike receptors and nucleotide-binding oligomerization domain proteins. PRRs initiate signal transduction pathways that include mitogen-activated protein kinase (MAPK) cascades that activate defencerelated transcription factors. This results in induction of proinflammatory cytokines in animals, and hallmarks of defence …

Mesa, A Novel Fungal Protein Required For The Stabilization Of Polarity Axes In Aspergillus Nidulans, Claire L. Pearson, Kaimei Xu, Kathryn E. Sharpless, Steven D. Harris

Department of Plant Pathology: Faculty Publications

The Aspergillus nidulans proteome possesses a single formin, SepA, which is required for actin ring formation at septation sites and also plays a role in polarized morphogenesis. Previous observations imply that complex regulatory mechanisms control the function of SepA and ensure its correct localization within hyphal tip cells. To characterize these mechanisms, we undertook a screen for mutations that enhance sepA defects. Of the mutants recovered, mesA1 causes the most dramatic defect in polarity establishment when SepA function is compromised. In a wild-type background, mesA1 mutants undergo aberrant hyphal morphogenesis, whereas septum formation remains unaffected. Molecular characterization revealed that MesA …