Plant Pathology Commons^™

Meloidogyne Spp. Infecting Ornamental Plants In Florida, J. A. Brito, R. Kaur, R. Cetintas, J. D. Stanley, M. L. Mendes, Thomas O. Powers, D. W. Dickson

Department of Plant Pathology: Faculty Publications

A total of 206 root samples were collected from ornamental plants growing in ornamental nurseries and various landscapes in Florida. Isozyme phenotypes, especially esterase (EST) and malate dehydrogenase (MDH) were the main methods used to identify the root-knot nematode species. When needed, the morphology of female perineal patterns, morphometric characters and mitochondrial DNA were used to aid in the identification. Six Meloidogyne spp., M. arenaria , M. floridensis , M. graminis , M. incognita , M. javanica and M. mayaguensis were found infecting ornamental plants in Florida. As previously reported EST activity was of highest diagnostic value to identify Meloidogyne …

Crystal Structure Of A Virus-Encoded Putative Glycosyltransferase, Yi Xiang, Ulrich Baxa, Ying Zhang, Alasdair C. Steven, Gentry L. Lewis, James L. Van Etten, Michael G. Rossmann

James Van Etten Publications

The chloroviruses (family Phycodnaviridae), unlike most viruses, encode some, if not most, of the enzymes involved in the glycosylation of their structural proteins. Annotation of the gene product B736L from chlorovirus NY-2A suggests that it is a glycosyltransferase. The structure of the recombinantly expressed B736L protein was determined by X-ray crystallography to 2.3-Å resolution, and the protein was shown to have two nucleotide-binding folds like other glycosyltransferase type B enzymes. This is the second structure of a chlorovirus-encoded glycosyltransferase and the first structure of a chlorovirus type B enzyme to be determined. B736L is a retaining enzyme and belongs …

Importance Of Myxomycetes In Biological Research And Teaching, Harold W. Keller, Sydney E. Everhart

Department of Plant Pathology: Faculty Publications

Myxomycetes, the true slime molds, are highlighted in research and teaching that emphasizes various stages of the life cycle as experimental models. Past and current phylogenetic classifications of Myxomycetes on the tree of life are presented. Life cycle stages are illustrated, described, and discussed. Simple laboratory demonstrations and experiments are described that include spore germination, spore release, and moist chamber cultures utilizing organic matter from various microhabitats. Novel compounds isolated from fruiting bodies and plasmodia of 22 myxomycete species are tabulated, some of which exhibit biological activity that function as antibiotics, antimicrobials, and are cytotoxic to cancer cells. Aeroallergens include …

Shiga Toxin Is Transported Into The Nucleoli Of Intestinal Epithelial Cells Via A Carrier-Dependent Process, Boris Baibakov, Rakhilya Murtazina, Christian Elowsky, Francis M. Giardiello, Olga Kovbasnjuk

Department of Plant Pathology: Faculty Publications

Shiga toxin (Stx) produced by the invasive Shigella dysenteriae serotype 1 (S. dysenteriae1) causes gastrointestinal and kidney complications. It has been assumed that Stx is released intracellularly after enterocyte invasion by S. dysenteriae1. However, there is little information about Stx distribution inside S. dysenteriae1-infected enterocytes. Here, we use intestinal epithelial T84 cells to characterize the trafficking of Stx delivered into the cytosol, in ways that mimic aspects of S. dysenteriae1 infection. We find that cytoplasmic Stx is transported into nucleoli. Stx nucleolar movement is carrier- and energy-dependent. Stx binding to the nucleoli of normal human …

Summer Heat And An Epidemic Of Cytospora Canker Of Alnus, James J. Worrall, Gerard C. Adams, Sarah C. Tharp

Department of Plant Pathology: Faculty Publications

An epidemic of cytospora canker [Valsa melanodiscus, anamorph Cytospora umbrina] is associated with dieback and mortality of Alnus incana ssp. tenuifolia in the Southern Rocky Mountains and had begun by the late 1980s. Isolations showed that inoculum was often abundant on bark and bud surfaces even in winter, especially near diseased stems. The pathogen was occasionally isolated from internal tissues of dormant buds and asymptomatic wood and phloem. In infected stems, the pathogen was detected up to 5 cm beyond visible canker margins. The data suggest that the pathogen can cause latent infections, but the infection court …

Turnover Of Mature Mirnas And Sirnas In Plants And Algae, Heriberto Cerutti, Fadia Ibrahim

Center for Plant Science Innovation: Faculty Publications

rnicroRNAs (miRNAs) and small interfering RNAs (siRNAs) play important roles in gene regulation and defense responses against transposons and viruses in eukaryotes. These small RNAs generally trigger the silencing of cognate sequences through a variety of mechanisms, including RNA degradation, translational inhibition, and transcriptional repression. In the past few years, the synthesis and the mode of action of miRNAs and siRNAs have attracted great attention. However, relatively little is known about mechanisms of quality control during small RNA biogenesis as well as those that regulate mature small RNA stability. Recent studies in Arabidopsis thaliana and Caenorhahditis elegans have implicated 3′-to-5′ …

Translational Inhibition By Micrornas In Plants, Bin Yu, Hai Wang

Center for Plant Science Innovation: Faculty Publications

MicroRNAs (miRNAs) are 21–24 nucleotide riboregulators, which selectively repress gene expression through transcript cleavage and/or translational inhibition. It was thought that most plant miRNAs act through target transcript cleavage due to the high degree of complementarity between miRNAs and their targets. However, recent studies have suggested widespread translational inhibition by miRNAs in plants. The mechanisms underlining translational inhibition by plant miRNAs are largely unknown, but existing evidence has indicated that plants and animals share some mechanistic similarity of translational inhibition. Translational inhibition by miRNAs has been shown to regulate floral patterning, floral timing, and stress responses. This chapter covers recent …

The Pathogenicity Determinant Of Citrus Tristeza Virus Causing The Seedling Yellows Syndrome Maps At The 3′-Terminal Region Of The Viral Genome, Maria R. Albiach-Marti, Cecile J. Robertson, Siddarame Gowda, Satyanarayana Tatineni, Belen Belliure, Stephen M. Garnsey, Svetlana Y. Folimonova, Pedro Moreno, William O. Dawson

Department of Plant Pathology: Faculty Publications

Citrus tristeza virus (CTV) (genus Closterovirus, family Closteroviridae) causes some of the more important viral diseases of citrus worldwide. The ability to map disease-inducing determinants of CTV is needed to develop better diagnostic and disease control procedures. A distinctive phenotype of some isolates of CTV is the ability to induce seedling yellows (SY) in sour orange, lemon and grapefruit seedlings. In Florida, the decline isolate of CTV, T36, induces SY, whereas a widely distributed mild isolate, T30, does not. To delimit the viral sequences associated with the SY syndrome, we created a number of T36/T30 hybrids by substituting T30 …

Heterologous Minor Coat Proteins Of Citrus Tristeza Virus Strains Affect Encapsidation, But The Coexpression Of Hsp70h And P61 Restores Encapsidation To Wild-Type Levels, Satyanarayana Tatineni, Siddarame Gowda, William O. Dawson

Department of Plant Pathology: Faculty Publications

The long flexuous bipolar virions of Citrus tristeza virus (CTV), a Closterovirus, are encapsidated with two capsid proteins at opposite ends: the minor coat protein (CPm) encapsidates the 5′ 630 nts of the genomic RNA and the major coat protein encapsidates the remainder of the genome. In this study, we found encapsidation of CTV CPm in the absence of other assembly-related proteins is highly specific in contrast to most plant viruses that allow virion assembly by a range of heterologous coat proteins. Heterologous CPms with 95–96% amino acid identity from related strains in CTV-CPm, a replicon with CPm as …

Soil And Root Populations Of Fluorescent Pseudomonas Spp. Associated With Seedlings And Field-Grown Plants Are Affected By Sorghum Genotype, Deanna L. Funnell-Harris, Jeffrey F. Pedersen, Scott E. Sattler

Department of Plant Pathology: Faculty Publications

Sorghum [Sorghum bicolor (L.) Moench] is valued for bioenergy, feed and food. Potential of sorghum genotypes to support differing populations of root- and soil-associated fluorescent Pseudomonas spp. or Fusarium spp., in two soils, was assessed. Culturable pseudomonads were enumerated from roots and soil of sorghum (Redlan and RTx433) and wheat (Lewjain) seedlings repeatedly grown in cycled soils in the growth chamber. Pseudomonads and Fusarium spp. were assessed from roots and soil of field-grown sorghum along with biological control traits hydrogen cyanide (HCN) and 2,4-diacetylphlorogluconol (phl) production. After four 4-week cycles, soil associated with Redlan seedlings had greater numbers …

Brown Midrib Mutations And Their Importance To The Utilization Of Maize, Sorghum, And Pearl Millet Lignocellulosic Tissues, Scott E. Sattler, Deanna L. Funnell-Harris, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Brown midrib mutants have been isolated in maize (Zea mays), sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) arising by either spontaneous or chemical mutagenesis. The characteristic brown coloration of the leaf mid veins is associated with reduced lignin content and altered lignin composition, traits useful to improve forage digestibility for livestock. Brown midrib phenotype is correlated with two homologous loci in maize (bm1 and bm3) and sorghum (bmr6 and bmr12), which encode cinnamyl alcohol dehydrogenase (CAD) and a caffeic O-methyl transferase (COMT). These enzymes are involved in the last …

Microarray Analysis Of Paramecium Bursaria Chlorella Virus 1 Transcription, Giane M. Yanai-Balser, Garry A. Duncan, James D. Eudy, Dong Wang, Xiao Li, Irina V. Agarkova, David D. Dunigan, James L. Van Etten

James Van Etten Publications

Paramecium bursaria chlorella virus 1 (PBCV-1), a member of the family Phycodnaviridae, is a large doublestranded DNA, plaque-forming virus that infects the unicellular green alga Chlorella sp. strain NC64A. The 330-kb PBCV-1 genome is predicted to encode 365 proteins and 11 tRNAs. To monitor global transcription during PBCV-1 replication, a microarray containing 50-mer probes to the PBCV-1 365 protein-encoding genes (CDSs) was constructed. Competitive hybridization experiments were conducted by using cDNAs from poly(A)- containing RNAs obtained from cells at seven time points after virus infection. The results led to the following conclusions: (i) the PBCV-1 replication cycle is temporally …

Upper Canopy Collection And Identification Of Grapevines (Vitis) From Selected Forests In The Southeastern United States, Sydney E. Everhart

Department of Plant Pathology: Faculty Publications

Woody grapevines (Vitis spp.) are common in the deciduous forests of the southeastern United States. Their growth habit makes leaf collection challenging and polymorphic leaves make identification of species difficult. Mature grapevines can grow up to 48 cm in diameter at breast height and reach the upper canopy of trees more than 35 m in height. Leaf morphology is the most readily available character used for species identification. However, most mature grapevines do not produce leaves below the upper canopy and if they do, these leaves are morphologically indistinguishable from other species. In order to sample leaves from …

Regulation Of Septum Formation By The Bud3–Rho4 Gtpase Module In Aspergillus Nidulans, Haoyu Si, Daniela Justa-Schuch, Stephan Seiler, Steven D. Harris

Department of Plant Pathology: Faculty Publications

The ability of fungi to generate polarized cells with a variety of shapes likely reflects precise temporal and spatial control over the formation of polarity axes. The bud site selection system of Saccharomyces cerevisiae represents the best-understood example of such a morphogenetic regulatory system. However, the extent to which this system is conserved in the highly polarized filamentous fungi remains unknown. Here, we describe the functional characterization and localization of the Aspergillus nidulans homolog of the axial bud site marker Bud3. Our results show that AnBud3 is not required for polarized hyphal growth per se, but is involved in septum …

An In Vitro Method For The Analysis Of Infection-Related Morphogenesis In Fusarium Graminearum, William R. Rittenour, Steven D. Harris

Department of Plant Pathology: Faculty Publications

Fusarium graminearum is a significant pathogen of many cereal crops. With its genetic tractability, ease of culture, genome sequence availability and economic significance, F. graminearum has become the subject of intensive molecular research. Although molecular tools have been developed to enhance research into virulence determinants of F. graminearum, simple assays for infection-related development are lacking. As such, the objective of this study was to develop an in vitro protocol for the analysis of infection-related morphogenesis in F. graminearum. We demonstrate that two morphologically distinct hyphal structures are produced by F. graminearum during the invasion of detached wheat glumes: subcuticular hyphae …

Whole Genome Wide Expression Profiles Of Vitis Amurensis Grape Responding To Downy Mildew By Using Solexa Sequencing Technology, Jiao Wu, Yali Zhang, Huiqin Zhang, Hong Huang, Kevin M. Folta, Jiang Lu

School of Information Faculty Publications

Background: Downy mildew (DM), caused by pathogen Plasmopara viticola (PV) is the single most damaging disease of grapes (Vitis L.) worldwide. However, the mechanisms of the disease development in grapes are poorly understood. A method for estimating gene expression levels using Solexa sequencing of Type I restriction-endonuclease-generated cDNA fragments was used for deep sequencing the transcriptomes resulting from PV infected leaves of Vitis amurensis Rupr. cv. Zuoshan-1. Our goal is to identify genes that are involved in resistance to grape DM disease.

Results: Approximately 8.5 million (M) 21-nt cDNA tags were sequenced in the cDNA library derived from PV pathogen-infected …

Population- And Genome-Specific Patterns Of Linkage Disequilibrium And Snp Variation In Spring And Winter Wheat (Triticum Aestivum L.), Shiaoman Chao, Jorge Dubcovsky, Jan Dvorak, Ming-Cheng Luo, P. Stephen Baenziger, Rustam Matnyazov, Dale R. Clark, Luther E. Talbert, James A. Anderson, Susanne Dreisigacker, Karl Glover, Jianli Chen, Kim Campbell, Phil L. Bruckner, Jackie C. Rudd, Scott Haley, Brett F. Carver, Sid Perry, Mark E. Sorrells, Eduard D. Akhunov

Department of Plant Pathology: Faculty Publications

Background: Single nucleotide polymorphisms (SNPs) are ideally suited for the construction of high-resolution genetic maps, studying population evolutionary history and performing genome-wide association mapping experiments. Here, we used a genome-wide set of 1536 SNPs to study linkage disequilibrium (LD) and population structure in a panel of 478 spring and winter wheat cultivars (Triticum aestivum) from 17 populations across the United States and Mexico.

Results: Most of the wheat oligo pool assay (OPA) SNPs that were polymorphic within the complete set of 478 cultivars were also polymorphic in all subpopulations. Higher levels of genetic differentiation were observed among wheat …

Century-Old Mystery Of Puccinia Striiformis Life History Solved With The Identification Of Berberis As An Alternate Host, Yue Jin, Les J. Szabo, Martin Carson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The life history of Puccinia striiformis remains a mystery because the alternate host has never been identified. Inoculation of grasses using aeciospores from naturally infected Berberis chinensis and B. koreana resulted in infection on Poa pratensis, producing uredinia typical of stripe rust caused by P. striiformis. Analyses using real-time polymerase chain reaction and DNA sequence confirmed the rust fungus as P. striiformis. Pycnia and aecia were produced on B. chinensis, B. holstii, B. koreana, and B. vulgaris after inoculation using germinating telia of P. striiformis f. sp. tritici. Wheat inoculated with aeciospores from B. chinensis resulted in …

Isolation Of The Phycodnavirus Pbcv-1 By Biological Laser Printing, Lisa A. Fitzgerald, Peter K. Wu, James Gurnon, Justin C. Biffinger, Bradley R. Ringeisen, James L. Van Etten

Department of Plant Pathology: Faculty Publications

The Phycodnaviridae family of viruses is diverse genetically but similar morphologically. These viruses infect eukaryotic algal hosts from both fresh and marine waters, and are an important component of aqueous environments. They play important roles in the dynamics of algal blooms, nutrient cycling, algal community structure, and possibly gene transfer between organisms. As such, it is important to identify new viruses within the Phycodnaviridae family. Biological laser printing (BioLP) was used to isolate single virus particles from solution. BioLP prints droplets containing a single virus particle directly onto a host medium, thereby enabling viruses to be isolated from unmodified samples. …

Microarray Analysis Of Paramecium Bursaria Chlorella Virus 1 Transcription, Giane M. Yanai-Balser, Garry A. Duncan, James D. Eudy, Dong Wang, Xiao Li, Irina V. Agarkova, David Dunigan, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Paramecium bursaria chlorella virus 1 (PBCV-1), a member of the family Phycodnaviridae, is a large double-stranded DNA, plaque-forming virus that infects the unicellular green alga Chlorella sp. strain NC64A. The 330-kb PBCV-1 genome is predicted to encode 365 proteins and 11 tRNAs. To monitor global transcription during PBCV-1 replication, a microarray containing 50-mer probes to the PBCV-1 365 protein-encoding genes (CDSs) was constructed. Competitive hybridization experiments were conducted by using cDNAs from poly(A)- containing RNAs obtained from cells at seven time points after virus infection. The results led to the following conclusions: (i) the PBCV-1 replication cycle is temporally …