Plant Pathology Commons^™

Minimal Art: Or Why Small Viral K+ Channels Are Good Tools For Understanding Basic Structure And Function Relations, Gerhard Thiel, Dirk Baumeister, Indra Schroeder, Stefan M. Kast, James L. Van Etten, Anna Moroni

James Van Etten Publications

Some algal viruses contain genes that encode proteins with the hallmarks of K+ channels. One feature of these proteins is that they are less than 100 amino acids in size, which make them truly minimal for a K+ channel protein. That is, they consist of only the pore module present in more complex K+ channels. The combination of miniature size and the functional robustness of the viral K+ channels make them ideal model systems for studying how K+ channels work. Here we summarize recent structure/function correlates from these channels, which provide insight into functional properties such as gating, pharmacology and …

Managing Crop Diseases With Fungicides, Kay Ruden, Lawrence E. Osborne

SDSU Extension Fact Sheets

This guide contains a list of fungicides labeled for use in South Dakota at the time of publication. The list is dynamic and prone to frequent changes. It therefore should not be considered as a substitute for label information. Always read and follow label directions for approved uses of these products, and check with the South Dakota Department of Agriculture for up-to-date product registration information.

Structural And Functional Analysis Of The Type Iii Secretion System From Pseudomonas Fluorescens Q8r1-96, Dmitri V. Mavrodi, Anna Joe, Olga V. Mavrodi, Karl A. Hassan, David M. Weller, Ian T. Paulsen, Joyce E. Loper, James R. Alfano, Linda S. Thomashow

Center for Plant Science Innovation: Faculty Publications

Pseudomonas fluorescens Q8r1-96 represents a group of rhizosphere strains responsible for the suppressiveness of agricultural soils to take-all disease of wheat. It produces the antibiotic 2,4-diacetylphloroglucinol and aggressively colonizes the roots of cereal crops. In this study, we analyzed the genome of Q8r1-96 and identified a type III protein secretion system (T3SS) gene cluster that has overall organization similar to that of the T3SS gene cluster of the plant pathogen Pseudomonas syringae. We also screened a collection of 30 closely related P. fluorescens strains and detected the T3SS genes in all but one of them. The Q8r1-96 genome contained …

Mpk6, Sphinganine And The Lcb2a Gene From Serine Palmitoyltransferase Are Required In The Signaling Pathway That Mediates Cell Death Induced By Long Chain Bases In Arabidopsis, Mariana Saucedo-García, Arturo Guevara-Garcia, Ariadna González-Solís, Felipe Cruz-García, Sonia Vázquez-Santana, Jennifer E. Markham, M. Guadalupe Lozano-Rosas, Charles R. Dietrich, Maricela Ramos-Vega, Edgar B. Cahoon, Marina Gavilanes-Ruíz

Center for Plant Science Innovation: Faculty Publications

• Long chain bases (LCBs) are sphingolipid intermediates acting as second messengers in programmed cell death (PCD) in plants. Most of the molecular and cellular features of this signaling function remain unknown.

• We induced PCD conditions in Arabidopsis thaliana seedlings and analyzed LCB accumulation kinetics, cell ultrastructure and phenotypes in serine palmitoyltransferase (spt), mitogen-activated protein kinase (mpk), mitogenactivated protein phosphatase (mkp1) and lcb-hydroxylase (sbh) mutants.

• The lcb2a-1 mutant was unable to mount an effective PCD in response to fumonisin B1 (FB1), revealing that the LCB2a gene is essential for the …

A Plant Dj-1 Homolog Is Essential For Arabidopsis Thaliana Chloroplast Development, Jiusheng Lin, Tara J. Nazarenus, Jeanine L. Frey, Xinwen Liang, Mark A. Wilson, Julie M. Stone

Center for Plant Science Innovation: Faculty Publications

Protein superfamilies can exhibit considerable diversification of function among their members in various organisms. The DJ-1 superfamily is composed of proteins that are principally involved in stress response and are widely distributed in all kingdoms of life. The model flowering plant Arabidopsis thaliana contains three close homologs of animal DJ-1, all of which are tandem duplications of the DJ-1 domain. Consequently, the plant DJ-1 homologs are likely pseudo-dimeric proteins composed of a single polypeptide chain. We report that one A. thaliana DJ-1 homolog (AtDJ1C) is the first DJ-1 homolog in any organism that is required for viability. Homozygous disruption of …

Two Distinct Roles Of Arabidopsis Homolog Of Trithorax1 (Atx1) At Promoters And Within Transcribed Regions Of Atx1-Regulated Genes, Yong Ding, Zoya Avramova, Michael E. Fromm

Center for Plant Science Innovation: Faculty Publications

The Arabidopsis thaliana trithorax-like protein, ATX1, shares common structural domains, has similar histone methyltransferase (HMT) activity, and belongs in the same phylogenetic subgroup as its animal counterparts. Most of our knowledge of the role of HMTs in trimethylating lysine 4 of histone H3 (H3K4me3) in transcriptional regulation comes from studies of yeast and mammalian homologs. Little is known about the mechanism by which ATX1, or any other HMT of plant origin, affects transcription. Here, we provide insights into how ATX1 influences transcription at regulated genes, playing two distinct roles. At promoters, ATX1 is required for TATA binding protein (TBP) and …

Structure Function Analysis Of An Adp-Ribosyltransferase Type Iii Effector And Its Rna-Binding Target In Plant Immunity, Byeong-Ryool Jeong, Yan Lin, Anna Joe, Ming Guo, Christin Korneli, Huirong Yang, Ping Wang, Min Yu, Ronald Cerny, Dorothee Staiger, James R. Alfano, Yanhui Xu

Center for Plant Science Innovation: Faculty Publications

Background: HopU1 ADP-ribosylates GRP7, suppressing plant immunity.

Results: The HopU1 structure has two novel loops required for GRP7 recognition, and HopU1 ribosylates GRP7 at an arginine in position 49 disrupting its function.

Conclusion: HopU1 targets a conserved arginine in GRP7, disabling its ability to bind immunity-related RNA.

Significance: The mechanistic details of how HopU1 recognizes its substrate reveal how HopU1 contributes to pathogenesis.

Functional Hak/Kup/Kt-Like Potassium Transporter Encoded By Chlorella Viruses, Timo Greiner, José Ramos, Maria C. Alvarez, James Gurnon, Ming Kang, James L. Van Etten, Anna Moroni, Gerhard Thiel

James Van Etten Publications

Chlorella viruses are a source of interesting membrane transport proteins. Here we examine a putative K+ transporter encoded by virus FR483 and related chlorella viruses. The protein shares sequence and structural features with HAK/KUP/KT-like K+ transporters from plants, bacteria and fungi. Yeast complementation assays and Rb+ uptake experiments show that the viral protein, termed HAKCV (high-affinity K+ transporter of chlorella virus), is functional, with transport characteristics that are similar to those of known K+ transporters. Expression studies revealed that the protein is expressed as an early gene during viral replication, and proteomics data indicate that it is not packaged in …

Characterization Of Viral And Host Proteins And Rna Elements In Tombusvirus Replication, Kunj Bihari Pathak

Theses and Dissertations--Plant Pathology

Two thirds of plant viruses are positive-strand RNA viruses including the family Tombusviridae. One of the best-studied members of this family is Tomato bushy stunt virus (TBSV). Like many other viruses, TBSV has much fewer genes when compared to its hosts’ genome. Nevertheless, TBSV utilizes its genome very judiciously. To compensate for a lack of many proteins of its own, it codes for multi-functional replication protein p33 and also co-opts host factors to facilitate its replication.

By using recombinant replication proteins p33 and p92 containing single amino acid changes in protein-protein interaction domains (S1 and S2), I demonstrated that the …

Efficient And Stable Expression Of Gfp Through Wheat Streak Mosaic Virus-Based Vectors In Cereal Hosts Using A Range Of Cleavage Sites: Formation Of Dense Fluorescent Aggregates For Sensitive Virus Tracking, Satyanarayana Tatineni, Anthony J. Mcmechan, Gary L. Hein, Roy French

Department of Plant Pathology: Faculty Publications

A series of Wheat streak mosaic virus (WSMV)-based expression vectors were developed by engineering a cycle 3 GFP (GFP) cistron between P1 and HC-Pro cistrons with several catalytic/cleavage peptides at the Cterminus of GFP. WSMV-GFP vectors with the Foot-and-mouth disease virus 1D/2A or 2A catalytic peptides cleaved GFP from HC-Pro but expressed GFP inefficiently. WSMV-GFP vectors with homologous NIa-Pro heptapeptide cleavage sites did not release GFP from HC-Pro, but efficiently expressed GFP as dense fluorescent aggregates. However, insertion of one or two spacer amino acids on either side of NIb/CP heptapeptide cleavage site or deletion in HC-Pro cistron improved processing …

Another Really, Really Big Virus, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Viruses with genomes larger than 300 kb and up to 1.2 Mb, which encode hundreds of proteins, are being discovered and characterized with increasing frequency. Most, but not all, of these large viruses (often referred to as giruses) infect protists that live in aqueous environments. Bioinformatic analyses of metagenomes of aqueous samples indicate that large DNA viruses are quite common in nature and await discovery. One issue that is perhaps not appreciated by the virology community is that large viruses, even those classified in the same family, can differ significantly in morphology, lifestyle, and gene complement. This brief commentary, which …

Motus, Morphology, And Biodiversity Estimation: A Case Study Using Nematodes Of The Suborder Criconematina And A Conserved 18s Dna Barcode, Thomas O. Powers, Timothy Harris, Rebecca Higgins, Peter Mullin, Lisa Sutton, Kirsten Powers

Department of Plant Pathology: Faculty Publications

DNA barcodes are increasingly used to provide an estimate of biodiversity for small, cryptic organisms like nematodes. Nucleotide sequences generated by the barcoding process are often grouped, based on similarity, into molecular operational taxonomic units (MOTUs). In order to get a better understanding of the taxonomic resolution of a 3’ 592-bp 18S rDNA barcode, we have analyzed 100 MOTUs generated from 214 specimens in the nematode suborder Criconematina. Previous research has demonstrated that the primer set for this barcode reliably amplifies all nematodes in the Phylum Nematoda. Included among the Criconematina specimens were 25 morphologically described species representing 12 genera. …

Economic Returns From Fungicide Application To Control Foliar Fungal Diseases In Winter Wheat, Stephen N. Wegulo, Michael V. Zwingman, Julie A. Breathnach, P. Stephen Baenziger

Department of Plant Pathology: Faculty Publications

Fungicides are commonly applied to control foliar fungal diseases of winter wheat in the central Great Plains of the United States and often are routinely recommended. However, economic benefits from fungicide application in winter wheat have rarely been quantified in this region. A total of eight field experiments were conducted in 2006 and 2007 in Nebraska, USA to quantify yield increases from fungicide applications to control foliar fungal diseases in winter wheat. Experiments were conducted at the same four locations (Mead, Clay Center, North Platte and Sidney) in both years. The fungicides used were azoxystrobin + propiconazole, pyraclostrobin, propiconazole, azoxystrobin …

Presence Of Fusarium Spp. In Air And Soil Associated With Sorghum Fields, Deanna L. Funnell-Harris, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Sorghum grain, valuable for feed, food, and bioenergy, can be colonized by several Fusarium spp.; therefore, it was of interest to identify possible sources of conidia. Analysis of air and soil samples provided evidence for the presence of propagules from Fusarium genotypes that may cause grain infections. Soil population estimates of members of the Gibberella fujikuroi species complex, that includes sorghum pathogens and other Fusarium spp., suggested that adequate inoculum for systemic infections was present. Conidia in air samples within two sorghum fields were collected by passive trapping for 2 years. Subsampled Fusarium isolates indicated that numbers of G. fujikuroi …

First Report Of Goss's Bacterial Wilt And Leaf Blight (Clavibacter Michiganensis Subsp. Nebraskensis) Of Corn In Texas, K. A. Korus, A. D. Timmerman, R. D. French-Monar, T. A. Jackson

Department of Plant Pathology: Faculty Publications

In September 2009, the University of Nebraska–Lincoln Plant and Pest Diagnostic Clinic received leaf samples of hybrid corn (Zea mays L.) displaying long, necrotic lesions with wavy margins. The lesions had discontinuous water-soaked spots that are indicative of Goss's bacterial wilt and leaf blight. The symptomatic leaves were submitted from Dallam County, located in the Texas Panhandle (northwest Texas). According to the USDA Farm Service Agency and the National Agricultural Statistics Service, in 2009 Dallam County had 54,025 ha planted to corn. This is approximately 19% of the total corn planted in the 26 counties in the Texas Panhandle …

Effects Of Integrating Cultivar Resistance And Fungicide Application On Fusarium Head Blight And Deoxynivalenol In Winter Wheat, Stephen N. Wegulo, William W. Bockus, John Hernandez Nopsa, Erick D. De Wolf, Kent M. Eskridge, Kamaranga H. S. Peiris, Floyd E. Dowell

Department of Plant Pathology: Faculty Publications

Fusarium head blight (FHB) or scab, incited by Fusarium graminearum, can cause significant economic losses in small grain production. Five field experiments were conducted from 2007 to 2009 to determine the effects on FHB and the associated mycotoxin deoxynivalenol (DON) of integrating winter wheat cultivar resistance and fungicide application. Other variables measured were yield and the percentage of Fusarium-damaged kernels (FDK). The fungicides prothioconazole + tebuconazole (formulated as Prosaro 421 SC) were applied at the rate of 0.475 liters/ha, or not applied, to three cultivars (experiments 1 to 3) or six cultivars (experiments 4 and 5) differing in their …

Characterization Of Three-Dimensional Spatial Aggregation And Association Patterns Of Brown Rot Symptoms Within Intensively Mapped Sour Cherry Trees, Sydney E. Everhart, Ashley Askew, Lynne Seymour, Imre J. Holb, Harald Scherm

Department of Plant Pathology: Faculty Publications

Characterization of spatial patterns of plant disease can provide insights into important epidemiological processes such as sources of inoculum, mechanisms of dissemination, and reproductive strategies of the pathogen population. While two-dimensional patterns of disease (among plants within fields) have been studied extensively, there is limited information on three-dimensional patterns within individual plant canopies. Reported here are the detailed mapping of different symptom types of brown rot (caused by Monilinia laxa) in individual sour cherry tree (Prunus cerasus) canopies, and the application of spatial statistics to the resulting data points to de-termine patterns of symptom aggregation and association. …

Giant Viruses, James L. Van Etten

James Van Etten Publications

The common view of viruses, mostly true, is of tiny burglars that sneak into cells, grab the biosynthetic controls and compel the cell to make huge numbers of progeny that break out of the cell and keep the replication cycle going. Viruses are supposed to be diminutive even compared to cells that are just a micrometer (1,000 nanometers) in diameter. They are supposed to travel light, making do with just a few well-adapted genes.

In 1992, a new microorganism was isolated from a power-plant cooling tower in Bradford, England, where Timothy Robotham, a microbiologist at Leeds Public Health Laboratory, was …

Role Of The Sexual Cycle In Development Of Genotypic And Phenotypic Diversity In Gibberella Zeae, Sladana Bec

Theses and Dissertations--Plant Pathology

Gibberella zeae (anamorph Fusarium graminearum) is a homothallic ascomycete pathogen that is responsible for causing Fusarium head blight (FHB) of wheat and small grains. In addition to causing a reduction in yield, harvested grain is frequently contaminated with trichothecene mycotoxins that are harmful for human and animal health. Use of wheat varieties with resistance to FHB is an important strategy to lower its impact. In order to produce varieties with durable resistance, we must understand the origin and degree of genetic diversity present in the pathogen population. In my research, I focused my efforts on an investigation of the …

Role Of Lipids In Tombusvirus Replication, Monika Sharma

University of Kentucky Doctoral Dissertations

Positive-strand RNA virus group are the most abundant among viruses affecting plants and animals. To successfully achieve replication, these viruses usurp or co-opt host proteins. To facilitate the discovery of host factors involved in Tomato bushy stunt virus (TBSV), yeast has been developed as a surrogate model host. Genome-wide approaches covering 95% of yeast genes, has revealed approximately hundred factors that could affect virus replication. Among the identified host factors, there are fourteen yeast genes, which affect/regulate lipid metabolism of the host.

One of the identified host gene is ERG25, which is an important factor for sterol biosynthesis pathway, affecting …