Life Sciences Commons^™

Regalia-Induced Resistance In Powdery Mildew-Infected Grapevine Plants Correlates With The Induction Of Chalcone Synthase, Thomas Crottogini

Horticulture and Crop Science

No abstract provided.

An Nadph-Dependent Genetic Switch Regulates Plant Infection By The Rice Blast Fungus, Richard A. Wilson, Robert P. Gibson, Cristian Quispe, Jennifer A. Littlechild, Nicholas J. Talbot

Fungal Molecular Plant-Microbe Interactions

To cause rice blast disease, the fungus Magnaporthe oryzae breaches the tough outer cuticle of the rice leaf by using specialized infection structures called appressoria. These cells allow the fungus to invade the host plant and proliferate rapidly within leaf tissue. Here, we show that a unique NADPH-dependent genetic switch regulates plant infection in response to the changing nutritional and redox conditions encountered by the pathogen. The biosynthetic enzyme trehalose-6-phosphate synthase (Tps1) integrates control of glucose-6-phosphate metabolism and nitrogen source utilization by regulating the oxidative pentose phosphate pathway, the generation of NADPH, and the activity of nitrate reductase. We report …

Analysis Of The Response Of Medicago Truncatula Calcium Oxalate Mutants To Abiotic Stress, Wayra Gabriela Navia-Gine

Graduate Theses and Dissertations

Calcium oxalate crystals are found in most plant species. In Medicago truncatula wild-type A17, crystals accumulate in leaves along the secondary veins and the only role attributed to them so far is defense against chewing insects. Calcium oxalate deficient (cod) mutants were isolated in M. truncatula; the cod mutants include cod5, which completely lack crystals in the leaves and cod6 that accumulates fewer and smaller crystals compared to A17. We analyzed gene expression in the cod mutants and A17 using GeneChip® Medicago Genome Arrays and found important differences in transcriptome between the three genotypes. In particular, we found a gene …

Population Variability Of Rotylenchulus Reniformis In Cotton Agroecosystems, Megan Leach

All Dissertations

Rotylenchulus reniformis, reniform nematode, is a highly variable species and an economically important pest in many cotton fields across the southeast. Rotation to resistant or poor host crops is a prescribed method for management of reniform nematode. An increase in the incidence and prevalence of the nematode in the United States has been reported over the last two decades. However it is not clear whether the observed increase is related to the emergence of novel populations that are more aggressive or have a higher fitness or shifts in host availability or susceptibility. The objectives of this research were to determine …

Fusarium Head Blight: Winter Wheat Cultivar Responses And Characterization Of Pathogen Isolates, John Fredy Hernandez Nopsa

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Fusarium head blight (FHB) is a destructive disease of wheat (Triticum aestivum L). FHB reduces yield and grain quality and causes accumulation of the mycotoxin deoxynivalenol (DON) in grain. Cultivar resistance is one of the most effective management strategies for FHB. Experiments were conducted to 1) identify winter wheat cultivars with resistance to FHB and DON accumulation, 2) determine the effect of winter wheat cultivar on the relationship between FHB and DON concentration, and 3) identify the major species of Fusarium causing FHB in Nebraska and characterize its isolates. Differences (P ≤ 0.05) were detected among cultivars in FHB …

Plant Ecophysiology Of Mycorrhizal Fungi, Gregory Keith Bartley Jr.

Gregory Keith Bartley Jr.

No abstract provided.

Making Of Viral Replication Organelles By Remodeling Interior Membranes, Zsuzsanna Sasvari, Peter D. Nagy

Plant Pathology Faculty Publications

Positive-stranded RNA (+RNA) viruses exploit host cell machinery by subverting host proteins and membranes and altering cellular pathways during infection. To achieve robust replication, some +RNA viruses, such as poliovirus (PV), build special intracellular compartments, called viral replication organelles. A recent work from the Altan-Bonnett laboratory [1] gave new insights into the formation of poliovirus replication organelles, which are unique subcellular structures containing many individual replication complexes as a result of dynamic cellular membrane remodeling.

Translation Elongation Factor 1a Facilitates The Assembly Of The Tombusvirus Replicase And Stimulates Minus-Strand Synthesis, Zhenghe Li, Judit Pogany, Steven Tupman, Anthony M. Esposito, Terri Goss Kinzy, Peter D. Nagy

Plant Pathology Faculty Publications

Replication of plus-strand RNA viruses depends on host factors that are recruited into viral replicase complexes. Previous studies showed that eukaryotic translation elongation factor (eEF1A) is one of the resident host proteins in the highly purified tombusvirus replicase complex. Using a random library of eEF1A mutants, we identified one mutant that decreased and three mutants that increased Tomato bushy stunt virus (TBSV) replication in a yeast model host. Additional in vitro assays with whole cell extracts prepared from yeast strains expressing the eEF1A mutants demonstrated several functions for eEF1A in TBSV replication: facilitating the recruitment of the viral RNA template …

Identification Of Sources Of Rhizoctonia Root Rot Resistance In Common Bean And Mapping A New Source Of Bean Rust Resistance From The Tertiary Gene Pool Of Common Bean, Pamela A. Peña-Perdomo

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

An efficient screening method was developed and used to identify bean lines resistant to Rhizoctonia Root Rot caused by Rhizoctonia solani Kuhn. Two sets of 163 and 111 lines previously evaluated for drought tolerance at Mitchell, NE and Isabela, PR were evaluated for Rhizoctonia Root Rot resistance under greenhouse conditions. This root rot data was also correlated with yield under drought stress and non stress conditions. In the first set of lines the rhizoctonia mean score ranged from 1.7 to 3.9; and in the second set the rhizoctonia mean score was between 2.6 and 5.7. There was no significant correlation …

The Combined Effect Of Environmental And Host Factors On The Emergence Of Viral Rna Recombinants, Hannah M. Jaag, Peter D. Nagy

Plant Pathology Faculty Publications

Viruses are masters of evolution due to high frequency mutations and genetic recombination. In spite of the significance of viral RNA recombination that promotes the emergence of drug-resistant virus strains, the role of host and environmental factors in RNA recombination is poorly understood. Here we report that the host Met22p/Hal2p bisphosphate-3'-nucleotidase regulates the frequency of viral RNA recombination and the efficiency of viral replication. Based on Tomato bushy stunt virus (TBSV) and yeast as a model host, we demonstrate that deletion of MET22 in yeast or knockdown of AHL, SAL1 and FRY1 nucleotidases/phosphatases in plants leads to increased TBSV recombination …

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 …

Plant Immunity Directly Or Indirectly Restricts The Injection Of Type Iii Effectors By The Pseudomonas Syringae Type Iii Secretion System, Emerson Crabill, Anna Joe, Anna Block, Jennifer M. Van Rooyen, James R. Alfano

Center for Plant Science Innovation: Faculty and Staff Publications

Plants perceive microorganisms by recognizing microbial molecules known as pathogen-associated molecular patterns (PAMPs) inducing PAMP-triggered immunity (PTI) or by recognizing pathogen effectors inducing effector-triggered immunity (ETI). The hypersensitive response (HR), a programmed cell death response associated with ETI, is known to be inhibited by PTI. Here, we show that PTI-induced HR inhibition is due to direct or indirect restriction of the type III protein secretion system’s (T3SS) ability to inject type III effectors (T3Es). We found that the Pseudomonas syringae T3SS was restricted in its ability to inject a T3E-adenylate cyclase (CyaA) injection reporter into PTI-induced tobacco (Nicotiana tabacum) cells. …

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 …

A Functional Calcium-Transporting Atpase Encoded By Chlorella Viruses, Maria Cristina Bonza, Holger Martin, Ming Kang, Gentry L. Lewis, Timo Greiner, Sonia Giacometti, James L. Van Etten, Maria Ida De Michelis, Gerhard Thiel, Anna Moroni

James Van Etten Publications

Calcium-transporting ATPases (Ca²⁺ pumps) are major players in maintaining calcium homeostasis in the cell and have been detected in all cellular organisms. Here, we report the identification of two putative Ca²⁺ pumps, M535L and C785L, encoded by chlorella viruses MT325 and AR158, respectively, and the functional characterization of M535L. Phylogenetic and sequence analyses place the viral proteins in group IIB of P-type ATPases even though they lack a typical feature of this class, a calmodulin-binding domain. A Ca²⁺ pump gene is present in 45 of 47 viruses tested and is transcribed during virus infection. Complementation analysis of …

Identification Of An L-Rhamnose Synthetic Pathway In Two Nucleocytoplasmic Large Dna Viruses, Madhu Parakkottil Chothi, Garry A. Duncan, Andrea Armirotti, Chantal Abergel, James R. Gurnon, James L. Van Etten, Cinzia Bernardi, Gianluca Damonte, Michela Tonetti

James Van Etten Publications

Nucleocytoplasmic large DNA viruses (NCLDVs) are characterized by large genomes that often encode proteins not commonly found in viruses. Two species in this group are Acanthocystis turfacea chlorella virus 1 (ATCV-1) (family Phycodnaviridae, genus Chlorovirus) and Acanthamoeba polyphaga mimivirus (family Mimiviridae), commonly known as mimivirus. ATCV-1 and other chlorovirus members encode enzymes involved in the synthesis and glycosylation of their structural proteins. In this study, we identified and characterized three enzymes responsible for the synthesis of the sugar L-rhamnose: two UDP-D-glucose 4,6-dehydratases (UGDs) encoded by ATCV-1 and mimivirus and a bifunctional UDP-4-keto-6-deoxy-D-glucose epimerase/reductase (UGER) from mimivirus. Phylogenetic …

Fragaria Species Grown In A Greenhouse Cropping System Chemigated By Phosfite® And Bacillus® In Subsidence Of Phytophthora Fragariae And Verticillium Dahliae, Russell L. Morgan

Earth and Soil Sciences

Strawberry yields depend directly on infestation of Phytophthora fragariae and Verticillium dahliae in correspondance to the use of Phosfite and Bacillus. The objective is to find understanding of newly administered techniques in prevention of Phytophthora fragariae and Verticillium dahliae and prohibiting the use of Methyl Bromide. Application of Phosfite and Bacillus on patented Fragariae species to identify utilization of P and ZN forms and their aid in prevention of Phytophthora and Verticillium species. In the Plots on the western bench the developmental symptoms of PRR disease were absent within all infested soil containers containing the FHS-1 crop. In the plots …

Overall Growth Of Tomato (Lycopersicon Esculentum L. Cv. Glacier) Inoculated With Species Of Glomus And Trichoderma Growing Under Greenhouse Conditions, Brian J. Adkins

Horticulture and Crop Science

The overall plant growth of tomato (Lycopersicon esculentum L. cv. Glacier) cultivated in greenhouse conditions along with inoculation treatments of beneficial fungi species were observed. This study included 2 brand name products containing species of fungi which include: 1)Botanicare Guardian TR containing Trichoderma harzianum 10,000,000 CFU/g, T. hamatum 10,000,000 CFU/g, T. koningii 10,000,000 CFU/g; and 2)Botanicare Guardian MY containing Glomus intraradices 57 propagules/g;G. fasiculatum 57 propagules/g; G. etunicatum 57 propagules/g; G. clarum 57 propagules/g. Treatments include: Treatments: 1) 2g Botanicare Guardian TR; 2) 2g Botanicare Guardian MY; 3) 1g Botanicare Guardian TR + 1g Botanicare Guardian MY; and …

Environmental Variables Influencing The Severity Of Pierce's Disease In California Grapevines, Christopher James Boisseranc

Master's Theses

This project was designed to correlate environmental variables with the development of Pierce’s Disease (PD), an infection caused by the gram negative bacterium Xylella fastidiosa (Xf), in grapes (Hopkins et al. 2002). PD is one of the most difficult crop pathogens to manage because it is vectored by insects and its continued presence in the vine is usually fatal. PD is influenced by the interaction of host, disease and vector, and probably many other environmental variables. The general objective was to study and identify the most important variables involved in the expression of Pierce’s Disease.

Over a two year period, …

Direct Polymerase Chain Reaction-Based Detection Of Cercospora Beticola In Field Soils, R. T. Lartey, T.C. Caesar-Tonthat, Andrew W. Lenssen, J. Eckhoff, S. L. Hanson, R. G. Evans

Andrew W. Lenssen

Cercospora beticola, the causal agent of Cercospora leaf spot of sugar beet, survives as pseudostromata in infected sugar beet residues in the soil. Under optimal conditions, overwintering propagules germinate and produce conidia that are dispersed as primary inoculum to initiate infection in sugar beet. We developed a polymerase chain reaction (PCR) technique for rapid detection of C. beticola in field soils. Total DNA was first isolated from soil amended with C. beticola culture using the PowerSoil DNA Kit. The purified DNA was subjected to PCR in Extract-N-Amp PCR mix with CBACTIN primers over 35 cycles. The amplified products were resolved …

Origin Of The Polycomb Repressive Complex 2 And Gene Silencing By An E(Z) Homolog In The Unicellular Alga Chlamydomonas, Scott Shaver, J. Armando Casas-Mollano, Ronald L. Cerny, Heriberto D. Cerutti

Center for Plant Science Innovation: Faculty and Staff Publications

Polycomb group proteins play an essential role in the maintenance of cell identity and the regulation of development in both animals and plants. The Polycomb Repressive Complex 2 (PRC2) is involved in the establishment of transcriptionally silent chromatin states, in part through its ability to methylate lysine 27 of histone H3 by the Enhancer of zeste [E(z)] subunit. The absence of PRC2 in unicellular model fungi and its function in the repression of genes vital for the development of higher eukaryotes led to the proposal that this complex may have evolved together with the emergence of multicellularity. However, we report …

Evaluation Of Genetic Diversity Of Flowering Dogwood (Cornus Florida L.) In The Eastern United States Using Microsatellites., Denita Hadziabdic

Doctoral Dissertations

Flowering dogwood (Cornus florida L.) populations have experienced severe declines caused by dogwood anthracnose in the past three decades. Mortality has ranged from 48 to 98%, raising the concern that genetic diversity of this native tree has been reduced significantly. Microsatellite data were used to evaluate the level and distribution of genetic variation throughout much of the native range of the tree. In the first conducted study, we found that genetic variation in areas affected by anthracnose was as high as or higher than areas without die-offs. We found evidence of four widespread, spatially contiguous genetic clusters. However, there was …

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 …

Sp277-O-Root Rots And Seedling Disease Of Beans And Peas, The University Of Tennessee Agricultural Extension Service

Insects, Pests, Plant Diseases and Weeds

Root rots, seed rots and damping off (death of seedlings before or after emergence) are major diseases of snap beans, lima beans and Southern peas. Seed rots and damping off are collectively referred to as seedling disease. These diseases cause poor stands and reduced plant growth and yield. The fungi that cause seedling disease and root rots can be found in most soils, but the occurrence of these diseases is unpredictable. When conditions are favorable for vigorous plant growth, root rot fungi do little damage. These fungi can survive in the soil for long periods and can be moved with …

Sp277-Y-Blossom-End Rot, The University Of Tennessee Agricultural Extension Service

Insects, Pests, Plant Diseases and Weeds

Blossom-end rot is a common problem of peppers, tomatoes and watermelons. It is most often seen in home gardens, but has been quite a factor in droughty years in commercial plantings of these crops.

Effects Of Fully Developed Vesicular Arbuscular Mycorrhizal Hyphae On Seed Germination Of Lolium Perenne, G Keith Bartley Jr, Richard J. Gualandi Jr, Robert M. Augé

Gregory Keith Bartley Jr.

Previous studies demonstrate that the inoculation of mycorrhizal spores in seeds can improve speed of germi- nation and establishment in grass seedlings. The universally positive effects of arbuscular mycorrhiza on plants suggest that fully developed mycorrhizal hyphae could potentially induce faster germination in seeds. This study presents data indicating that the inoculation of full grown hyphae in seeds of Lolium perenne inhibits speed of germination, independent of level of available soil nutrients. Daily measurements of seedling height between in- fected and non-infected plants at different starter fertilization rates in a sand profile showed that abuscular mycor- hiza influenced seeds emerged …

A Potential Plan Of Action For Emerald Ash Borer In Nebraska, Lee Wheeler

Department of Environmental Studies: Undergraduate Student Theses

Abstract Emerald Ash Borer (Agrilus planipennis) (EAB) is an invasive insect pest. It feeds on the cambium tissues of ash tree species. It was first discovered in the United States in 2002 in Detroit, Michigan. Their effects on ash trees are deadly, and it is quickly spreading across the Midwest. Nebraska has not yet been invaded, but confirmed findings continue getting closer and closer. The major problem facing Nebraskans, with regards to EAB, is how to begin preparations to prevent a dramatic economic loss when an infestation does occur. So, to address this problem, I have conducted street and park …

Distinct Evolutionary Histories Of The Dna-A And Dna-B Components Of Bipartite Begomoviruses, Rob W. Briddon, Basavaprabhu L. Patil, Basavaraj Bagewadi, Muhammad Shah Nawaz-Ul-Rehman, Claude M. Fauquet

Plant Pathology Faculty Publications

BACKGROUND: Viruses of the genus Begomovirus (family Geminiviridae) have genomes consisting of either one or two genomic components. The component of bipartite begomoviruses known as DNA-A is homologous to the genomes of all geminiviruses and encodes proteins required for replication, control of gene expression, overcoming host defenses, encapsidation and insect transmission. The second component, referred to as DNA-B, encodes two proteins with functions in intra- and intercellular movement in host plants. The origin of the DNA-B component remains unclear. The study described here was initiated to investigate the relationship between the DNA-A and DNA-B components of bipartite begomoviruses with a …