Life Sciences Commons^™

Increased Plant Uptake Of Nitrogen From 15N-Depleted Fertilizer Using Plant Growth-Promoting Rhizobacteria, A. O. Adesemoye, H. A. Torbert, J. W. Kloepper

Department of Plant Pathology: Faculty Publications

Harmful environmental effects resulting from fertilizer use have spurred research into integrated nutrient management strategies which can include the use of specific microorganisms to enhance nutrient use efficiency by plants. Some strains of plant growth-promoting rhizobacteria (PGPR) have been reported to enhance nutrient uptake by plants, but no studies with PGPR have used ¹⁵N isotope techniques to prove that the increased N in plant tissues came from the N applied as fertilizer. The current study was conducted to demonstrate that a model PGPR system can enhance plant uptake of fertilizer N applied to the soil using different rates of …

The Chlorella Variabilis Nc64a Genome Reveals Adaptation To Photosymbiosis, Coevolution With Viruses, And Cryptic Sex, Guillaume Blanc, Garry Duncan, Irina Agarkova, Mark Borodovsky, James Gurnon, Alan Kuo, Erika Lindquist, Susan Lucas, Jasmyn Pangilinan, Juergen Polle, Asaf Salamov, Astrid Terry, Takashi Yamada, David D. Dunigan, Igor V. Grigoriev, Jean-Michel Claverie, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Chlorella variabilis NC64A, a unicellular photosynthetic green alga (Trebouxiophyceae), is an intracellular photobiont of Paramecium bursaria and a model system for studying virus/algal interactions. We sequenced its 46-Mb nuclear genome, revealing an expansion of protein families that could have participated in adaptation to symbiosis. NC64A exhibits variations in GC content across its genome that correlate with global expression level, average intron size, and codon usage bias. Although Chlorella species have been assumed to be asexual and nonmotile, the NC64A genome encodes all the known meiosis-specific proteins and a subset of proteins found in flagella. We hypothesize that Chlorella might have …

Unique Functionality Of 22 Nt Mirnas In Triggering Rdr6-Dependent Sirna Biogenesis From Target Transcripts In Arabidopsis, Josh T. Cuperus, Alberto Carbonell, Noah Fahlgren, Hernan Garcia-Ruiz, Russell T. Burke, Atsushi Takeda, Christopher M. Sullivan, Sunny D. Gilbert, Taiowa A. Montgomery, James C. Carrington

Department of Plant Pathology: Faculty Publications

RNA interference pathways may involve amplification of secondary siRNAs by RNA-dependent RNA polymerases. In plants, RDR6-dependent secondary siRNAs arise from transcripts targeted by some microRNA (miRNA). Here, Arabidopsis thaliana secondary siRNA from mRNA, and trans-acting siRNA, are shown to be triggered through initial targeting by 22 nt miRNA that associate with AGO1. In contrast to canonical 21 nt miRNA, 22 nt miRNA primarily arise from foldback precursors containing asymmetric bulges. Using artificial miRNA constructs, conversion of asymmetric foldbacks to symmetric foldbacks resulted in production of 21 nt forms of miR173, miR472 and miR828. Both 21 and 22 nt forms associated …

Alteration In Lignin Biosynthesis Restricts Growth Of Fusarium Spp. In Brown Midrib Sorghum, Deanna L. Funnell-Harris, Jeffrey F. Pedersen, Scott E. Sattler

Department of Plant Pathology: Faculty Publications

To improve sorghum for bioenergy and forage uses, brown midrib (bmr)6 and -12 near-isogenic genotypes were developed in different sorghum backgrounds. The bmr6 and bmr12 grain had significantly reduced colonization by members of the Gibberella fujikuroi species complex compared with the wild type, as detected on two semiselective media. Fusarium spp. were identified using sequence analysis of a portion of the translation elongation factor (TEF) 1-α gene. The pathogens Fusarium thapsinum, F. proliferatum, and F. verticillioides, G. fujikuroi members, were commonly recovered. Other frequently isolated Fusarium spp. likely colonize sorghum asymptomatically. The χ2 analyses showed that the …

Vittatidera Zeaphila (Nematoda: Heteroderidae), A New Genus And Species Of Cyst Nematode Parasitic On Corn (Zea Mays), Ernest C. Bernard, Zafar A. Handoo, Thomas O. Powers, Patricia A. Donald, Robert D. Heinz

Department of Plant Pathology: Faculty Publications

A new genus and species of cyst nematode, Vittatidera zeaphila, is described from Tennessee. The new genus is superficially similar to Cactodera but is distinguished from other cyst-forming taxa in having a persistent lateral field in females and cysts, persistent vulval lips covering a circumfenestrate vulva, and subventral gland nuclei of the female contained in a separate small lobe. Infective juveniles (J2) are distinguished from all previously described Cactodera spp. by the short stylet in the second-stage juvenile (14-17 mm); J2 of Cactodera spp. have stylets at least 18 mm long. The new species also is unusual in that …

Dna Viruses: The Really Big Ones (Giruses), James L. Van Etten, Leslie C. Lane, David Dunigan

Department of Plant Pathology: Faculty Publications

Viruses with genomes greater than 300 kb and up to 1200 kb are being discovered with increasing frequency. These large viruses (often called giruses) can encode up to 900 proteins and also many tRNAs. Consequently, these viruses have more protein-encoding genes than many bacteria, and the concept of small particle/small genome that once defined viruses is no longer valid. Giruses infect bacteria and animals although most of the recently discovered ones infect protists. Thus, genome gigantism is not restricted to a specific host or phylogenetic clade. To date, most of the giruses are associated with aqueous environments. Many of these …

Wheat Cultivar-Specific Disease Synergism And Alteration Of Virus Accumulation During Co-Infection With Wheat Streak Mosaic Virus And Triticum Mosaic Virus, Satyanarayana Tatineni, Robert A. Graybosch, Gary L. Hein, Stephen N. Wegulo, Roy French

Department of Plant Pathology: Faculty Publications

Triticum mosaic virus (TriMV), the type member of the newly proposed Poacevirus genus, and Wheat streak mosaic virus (WSMV), the type member of Tritimovirus genus of the family Potyviridae, infect wheat naturally in the Great Plains and are transmitted by wheat curl mites. In this study, we examined the ability of these viruses to infect selected cereal hosts, and found several differential hosts between TriMV and WSMV. Additionally, we examined the interaction between WSMV and TriMV in three wheat cultivars at two temperature regimens (19 and 20 to 26°C), and quantified the virus concentration in single and double infections …

Arabidopsis Rna-Dependent Rna Polymerases And Dicer-Like Proteins In Antiviral Defense And Small Interfering Rna Biogenesis During Turnip Mosaic Virus Infection, Hernan Garcia-Ruiz, Atsushi Takeda, Elisabeth J. Chapman, Christopher M. Sullivan, Noah Fahlgren, Katherine J. Brempelis, James C. Carrington

Department of Plant Pathology: Faculty Publications

Plants respond to virus infections by activation of RNA-based silencing, which limits infection at both the single-cell and system levels. Viruses encode RNA silencing suppressor proteins that interfere with this response. Wild-type Arabidopsis thaliana is immune to silencing suppressor (HC-Pro)-deficient Turnip mosaic virus, but immunity was lost in the absence of DICER-LIKE proteins DCL4 and DCL2. Systematic analysis of susceptibility and small RNA formation in Arabidopsis mutants lacking combinations of RNA-dependent RNA polymerase (RDR) and DCL proteins revealed that the vast majority of virus derived small interfering RNAs (siRNAs) were dependent on DCL4 and RDR1, although full antiviral defense …

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 …

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 …

Deep And Comparative Transcriptome Analysis Of Rice Plants Infested By The Beet Armyworm (Spodoptera Exigua) And Water Weevil (Lissorhoptrus Oryzophilus), R. C. Venu, M. Sheshu Madhav, M. V. Sreerekha, Kan Nobuta, Yuan Zhang, Peter Carswell, Michael J. Boehm, B. C. Meyers, Kenneth L. Korth, Guo-Liang Wang

Department of Plant Pathology: Faculty Publications

The beet armyworm (Spodoptera exigua) and the rice water weevil (Lissorhoptrus oryzophilus) are two important insect pests in rice production. To identify insect-responsive genes in rice, we performed a deep transcriptome analysis of Nipponbare rice leaves infested with both beet armyworm and water weevil using massively parallel signature sequencing (MPSS). Many antisense, alternative, and novel transcripts were commonly and specifically induced and suppressed in the infested tissue. Key genes involved in the defense metabolic pathways such as salicylic acid and jasmonic acid biosynthesis pathways were up-regulated in the infested leaves. To validate theMPSS results, we analyzed …

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 …

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 …

Isolation Of The Phycodnavirus Pbcv-1 By Biological Laser Printing, Lisa A. Fitzgerald, Peter K. Wu, James R. 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. …

Morphological And Molecular Characterization Of Discocriconemella Inarata, An Endemic Nematode From North American Native Tallgrass Prairies, Thomas O. Powers, Timothy Harris, Rebecca Higgins, Lisa Sutton, Kirsten S. Powers

Department of Plant Pathology: Faculty Publications

Discocriconemella inarata, a plant parasitic nematode species originally discovered in a virgin tallgrass prairie in northwest Iowa, was re-examined by molecular and morphological analyses of topotype material. This species has never been recorded in cultivated fields and could potentially serve as an indicator for high quality prairie habitats. DNA sequence from a conserved 3’ portion of the 18S ribosomal gene exhibited an identical match between D. inarata topotype specimens and topotype specimens of Mesocriconema xenoplax from Fresno, California. Higher resolution sequence analyses using the internal transcribed spacer 1 (ITS1) and a portion of the mitochondrial gene cytochrome b (cytb) …

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 …

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. …

Initial Events Associated With Virus Pbcv-1 Infection Of Chlorella Nc64a, Gerhard Thiel, Anna Moroni, David Dunigan, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Chlorella viruses (or chloroviruses) are very large, plaque-forming viruses. The viruses are multilayered structures containing a large double-stranded DNA genome, a lipid bilayered membrane, and an outer icosahedral capsid shell. The viruses replicate in certain isolates of the coccal green alga, Chlorella. Sequence analysis of the 330-kbp genome of Paramecium bursaria Chlorella virus 1 (PBCV-1), the prototype of the virus family Phycodnaviridae, reveals <365 protein-encoding genes and 11 tRNA genes. Products of about 40% of these genes resemble proteins of known function, including many that are unexpected for a virus. Among these is a virus-encoded protein, called Kcv, which forms a functional K+ channel. This chapter focuses on the initial steps in virus infection and provides a plausible role for the function of the viral K+ channel in lowering the turgor pressure of the host. This step appears to be a prerequisite for delivery of the viral genome into the host.

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 …

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 …

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 …

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 …

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 …