Plant Pathology Commons^™

Chlorophyll Synthase Under Epigenetic Surveillance Is Critical For Vitamin E Synthesis, And Altered Expression Affects Tocopherol Levels In Arabidopsis, Chunyu Zhang, Wei Zhang, Guodong Ren, Denli Li, Rebecca E. Cahoon, Ming Chen, Yongming Zhou, Bin Yu, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty Publications

Chlorophyll synthase catalyzes the final step in chlorophyll biosynthesis: the esterification of chlorophyllide with either geranylgeranyl diphosphate or phytyl diphosphate (PDP). Recent studies have pointed to the involvement of chlorophyll-linked reduction of geranylgeranyl by geranylgeranyl reductase as a major pathway for the synthesis of the PDP precursor of tocopherols. This indirect pathway of PDP synthesis suggests a key role of chlorophyll synthase in tocopherol production to generate the geranylgeranyl-chlorophyll substrate for geranylgeranyl reductase. In this study, contributions of chlorophyll synthase to tocopherol formation in Arabidopsis (Arabidopsis thaliana) were explored by disrupting and altering expression of the corresponding gene …

Characterization Of A Novel Megabirnavirus From Sclerotinia Sclerotiorum Reveals Horizontal Gene Transfer From Single-Stranded Rna Virus To Double-Stranded Rna Virus, Minghong Wang, Yong Wang, Xiangzhong Sun, Jiasen Cheng, Yanping Fu, Huiquan Liu, Daohong Jiang, Said A. Ghabrial, Jiatao Xie

Plant Pathology Faculty Publications

Mycoviruses have been detected in all major groups of filamentous fungi, and their study represents an important branch of virology. Here, we characterized a novel double-stranded RNA (dsRNA) mycovirus, Sclerotinia sclerotiorum megabirnavirus 1 (SsMBV1), in an apparently hypovirulent strain (SX466) of Sclerotinia sclerotiorum. Two similarly sized dsRNA segments (L1- and L2-dsRNA), the genome of SsMBV1, are packaged in rigid spherical particles purified from strain SX466. The full-length cDNA sequence of L1-dsRNA/SsMBV1 comprises two large open reading frames (ORF1 and ORF2), which encode a putative coat protein and an RNA-dependent RNA polymerase (RdRp), respectively. Phylogenetic analysis of the RdRp domain …

Rust Diseases On Switchgrass (Panicum Virgatum), Ying Ma

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

Switchgrass (Panicum virgatum) is a perennial C₄ grass native to the central prairies of North America. Recent development of switchgrass as a sustainable biofuel feedstock has raised interest in diseases that could impact switchgrass, especially when grown under monoculture conditions. Among the known diseases of switchgrass, rust diseases are the most widespread and could potentially impact yield and biomass quality of new switchgrass cultivars. Two species of rust fungi, Uromyces graminicola and Puccinia emaculata, are known to infect switchgrass, with P. emaculata being the primary or sole rust pathogen on switchgrass in southern US states. The …

Osmotic Stress Induces Phosphorylation Of Histone H3 At Threonine 3 In Pericentromeric Regions Of Arabidopsis Thaliana, Zhen Wang, Juan Armando Casas-Mollano, Jianping Xu, Jean-Jack M. Riethoven, Chi Zhang, Heriberto Cerutti

Center for Plant Science Innovation: Faculty Publications

Histone phosphorylation plays key roles in stress-induced transcriptional reprogramming in metazoans but its function(s) in land plants has remained relatively unexplored. Here we report that an Arabidopsis mutant defective in At3g03940 and At5g18190, encoding closely related Ser/Thr protein kinases, shows pleiotropic phenotypes including dwarfism and hypersensitivity to osmotic/salt stress. The double mutant has reduced global levels of phosphorylated histone H3 threonine 3 (H3T3ph), which are not enhanced, unlike the response in the wild type, by drought-like treatments. Genome-wide analyses revealed increased H3T3ph, slight enhancement in trimethylated histone H3 lysine 4 (H3K4me3), and a modest decrease in histone H3 occupancy …

Osmotic Stress Induces Phosphorylation Of Histone H3 At Threonine 3 In Pericentromeric Regions Of Arabidopsis Thaliana, Zhen Wang, Juan Casas-Mollano, Jianping Xu, Jean-Jack Riethoven, Chi Zhang, Heriberto D. Cerutti

Center for Plant Science Innovation: Faculty Publications

Histone phosphorylation plays key roles in stress-induced transcriptional reprogramming in metazoans but its function(s) in land plants has remained relatively unexplored. Here we report that an Arabidopsis mutant defective in At3g03940 and At5g18190, encoding closely related Ser/Thr protein kinases, shows pleiotropic phenotypes including dwarfism and hypersensitivity to osmotic/salt stress. The double mutant has reduced global levels of phosphorylated histone H3 threonine 3 (H3T3ph), which are not enhanced, unlike the response in the wild type, by drought-like treatments. Genome-wide analyses revealed increased H3T3ph, slight enhancement in trimethylated histone H3 lysine 4 (H3K4me3), and a modest decrease in histone H3 occupancy …

Isolation Of Possible Biocontrol Endophytic Bacteria From Solanum Tuberosum Effective Against Streptomyces Scabies., Annie Flatley, Luke Ogle, Adam Noel, Erica Fraley, Alaxandra Goodman, Donna Becker

Poster Sessions

Use of biological control offers a cost effective and environmentally safe method for controlling plant diseases. Biocontrol agents that can colonize roots and live endophytically within plant tissue should allow for effective disease control. The goal of this research was to develop protocols to isolate putative Streptomyces species from potato stem and tuber tissue due to their ability to produce inhibitory compounds which could potentially reduce diseases caused by Streptomyces scabies. Endophyte isolation from Solanum tuberosum (potato) plants (stem and tuber tissues) that were grown in a biocontrol field trial were the focus of this study. Several surface …

Use Of Two Pathogen-Inhibiting Streptomyces Isolates For Biocontrol Of Scab Disease Of Raphanus Sativus, Tyler Park, Nichole Klingler, Adam Noel, Luke Ogle, Annie Flatley, Donna Becker

Poster Sessions

Streptomyces species are ubiquitous soil bacteria that are promising as biological control agents due to their prolific antibiotic production that can inhibit soil-borne plant pathogens. This includes Streptomyces scabies, which causes scab disease on underground storage organs. The goal of this research was to test two Streptomyces isolates that have known inhibitory and biocontrol abilities against S. scabies in a potato (Solanum tuberosum) agricultural system for their effectiveness in biocontrol of this pathogen in a radish (Raphanus sativus) greenhouse assay. Pathogenic S. scabies were mixed into either pasteurized or unpasteurized soil prior to planting. Radish …

Soybean Seed Quality And Vigor: Influencing Factors, Measurement, And Pathogen Characterization, Kimberly Ann Cochran

Graduate Theses and Dissertations

High seed vigor (SV), or the ability of seed to germinate and grow in a stressful environment is important, as many field emergence conditions are stressful for germination. Soybean SV can be affected by cultivar, seed storage environment conditions, the growing environment during seed development, crop management practices such as foliar fungicide applications, pathogens, and other factors. To assess the effects of some of these factors on soybean, the objectives of this work were to determine 1. the effect of cultivar and foliar azoxystrobin application on soybean yield, germination, vigor, microflora, and their relationships under harvest delay conditions; 2. if …

Pythium: Characterization Of Resistance In Soybean And Population Diversity, Keiddy Esperanza Urrea Romero

Graduate Theses and Dissertations

Pythium spp. are an important group of pathogens causing stand losses in Arkansas soybean production. New inoculation methods and advances in molecular techniques allow a better understanding of cultivar resistance and responses of Pythium communities to cultural practices. The objectives of this research were to i) characterize the resistance of soybean to P. aphanidermatum with two phenotyping assays that evaluated the seed rot phase of the disease; and ii) understand the effect of long term crop rotation on species diversity and iii) to determine the effect of location, temperature and continuous soybean and soybean-rice rotation on Pythium spp. diversity in …

Effect Of Nitrogen Fertilizer Rates And Two-Spotted Spider Mite Incidence On 'Strawberry Festival' Strawberry Cultivar Performance, Megan E. Mcgovern

Graduate Theses and Dissertations

The decline in strawberry (Fragaria x ananassa Duch.) production in Arkansas over the last 50 years has sparked an interest in the use of season extension techniques to improve yield and fruit quality. High tunnel strawberry production has the potential to become a profitable and sustainable production system; however, information on nutrient and pest management is limited.

The overall objective of this study was to determine the response of ‘St. Festival’ strawberry cultivar to different nitrogen fertilizer rates in order to develop a fertilization program for strawberries grown under high tunnel production systems. Experiments were conducted at the University of …

Evaluation Of Control Strategies For The Spread Of Citrus Greening, Vicente Valle Martinez

Theses and Dissertations - UTB/UTPA

Huanglongbing, also known as citrus greening, is a vector-based disease in citrus (with no cure known to date) that has drastically affected the citrus production in Florida in less than a decade and has been recently detected in Texas and California. In this paper, an epidemic model of the spatial spread of the disease is implemented among commercial and residential groves by taking into consideration the diffusion patterns of the psyllid vectors. A system of differential equations resembling one for malaria infection in humans is derived to evaluate different control methods such as quarantine, treatment, removal, foliar treatment, and pest …

Prokaryotic Diversity In The Rhizosphere Of Organic, Intensive, And Transitional Coffee Farms In Brazil, Adam Caldwell, Livia Silva, Cynthia Da Silva, Cleber Ouverney

Faculty Publications, Biological Sciences

Despite a continuous rise in consumption of coffee over the past 60 years and recent studies showing positive benefits linked to human health, intensive coffee farming practices have been associated with environmental damage, risks to human health, and reductions in biodiversity. In contrast, organic farming has become an increasingly popular alternative, with both environmental and health benefits. This study aimed to characterize and determine the differences in the prokaryotic soil microbiology of three Brazilian coffee farms: one practicing intensive farming, one practicing organic farming, and one undergoing a transition from intensive to organic practices. Soil samples were collected from 20 …

Combinatorial Effects Of Fatty Acid Elongase Enzymes On Nervonic Acid Production In Camelina Sativa, Dongxin Huai, Yuanyuan Zhang, Chunyu Zhang, Edgar B. Cahoon, Yongming Zhou

Center for Plant Science Innovation: Faculty Publications

Very long chain fatty acids (VLCFAs) with chain lengths of 20 carbons and longer provide feedstocks for various applications; therefore, improvement of VLCFA contents in seeds has become an important goal for oilseed enhancement. VLCFA biosynthesis is controlled by a multi-enzyme protein complex referred to as fatty acid elongase, which is composed of β-ketoacyl-CoA synthase (KCS), β-ketoacyl-CoA reductase (KCR), β-hydroxyacyl-CoA dehydratase (HCD) and enoyl reductase (ECR). KCS has been identified as the ratelimiting enzyme, but little is known about the involvement of other three enzymes in VLCFA production. Here, the combinatorial effects of fatty acid elongase enzymes on VLCFA production …

Characterization Of A Novel Clade Of Transporters In Phytophthora, Stephanie Padula, Paul F. Morris Dr, Howard Casey Cromwell Dr., Menaka Ariyaratne, Andrew Wagner

Honors Projects

The oomycete Phytophthora parasitica has a worldwide distribution and is an economically important pathogen of more than 100 species⁴. RNA-seq analysis showed that one gene, PPTG_16698 has the 5^th highest level of expression of all transport proteins in the zoospore stage, and is highly conserved throughout Phytophthora species. This project attempts to characterize the important biological role that PPTG_16698 plays in P. parasitica and other oomycetes. Three strategies have been implemented to accomplish this goal: growth analysis by heterologous expression in yeast, metabolite analysis in yeast, and construction of a GFP fusion protein to enable localization of …

Activation Of Tomato Bushy Stunt Virus Rna-Dependent Rna Polymerase By Cellular Heat Shock Protein 70 Is Enhanced By Phospholipids In Vitro, Judit Pogany, Peter D. Nagy

Plant Pathology Faculty Publications

Similar to other positive-strand RNA viruses, tombusviruses are replicated by the membrane-bound viral replicase complex (VRC). The VRC consists of the p92 virus-coded RNA-dependent RNA polymerase (RdRp), the viral p33 RNA chaperone, and several co-opted host proteins. In order to become a functional RdRp after its translation, the p92 replication protein should be incorporated into the VRC, followed by its activation. We have previously shown in a cell-free yeast extract-based assay that the activation of the Tomato bushy stunt virus (TBSV) RdRp requires a soluble host factor(s). In this article, we identify the cellular heat shock protein 70 (Hsp70) as …

Viral Sensing Of The Subcellular Environment Regulates The Assembly Of New Viral Replicase Complexes During The Course Of Infection, Peter D. Nagy

Plant Pathology Faculty Publications

Replication of plus-stranded RNA [(+)RNA] viruses depends on the availability of coopted host proteins and lipids. But, how could viruses sense the accessibility of cellular resources? An emerging concept based on tombusviruses, small plant viruses, is that viruses might regulate viral replication at several steps depending on what cellular factors are available at a given time point. I discuss the role of phospholipids, sterols, and cellular WW domain proteins and eukaryotic elongation factor 1A (eEF1A) in control of activation of the viral RNA-dependent RNA polymerase (RdRp) and regulation of the assembly of viral replicase complexes (VRCs). These regulatory mechanisms might …

Seasonal Activity And Sampling Methods For The Dectes Stem Borer, Dectes Texanus Leconte, In Nebraska Soybeans, Zachary D. Rystrom

Department of Entomology: Dissertations, Theses, and Student Research

The Dectes stem borer, Dectes texanus Leconte, has caused significant economic damage to soybean fields in south central Nebraska during recent years. Most economic injury occurs when soybean plants become susceptible to late season lodging due to larval girdling. Developing a comprehensive management plan for Dectes stem borer in Nebraska is limited by lack of knowledge of seasonal activity and effective sampling plans to monitor adult populations. Field studies were conducted in 2013 and 2014 to describe Dectes stem borer adult emergence patterns, female ovipositional period and adult densities in soybean fields. Calendar date predictions for adult emergence varied, while …

Gata-Dependent Glutaminolysis Drives Appressorium Formation In Magnaporthe Oryzae By Suppressing Tor Inhibition Of Camp/Pka Signaling, Margarita Marroquin-Guzman, Richard A. Wilson

Department of Plant Pathology: Faculty Publications

Fungal plant pathogens are persistent and global food security threats. To invade their hosts they often form highly specialized infection structures, known as appressoria. The cAMP/ PKA- and MAP kinase-signaling cascades have been functionally delineated as positive-acting pathways required for appressorium development. Negative-acting regulatory pathways that block appressorial development are not known. Here, we present the first detailed evidence that the conserved Target of Rapamycin (TOR) signaling pathway is a powerful inhibitor of appressorium formation by the rice blast fungus Magnaporthe oryzae. We determined TOR signaling was activated in an M. oryzae mutant strain lacking a functional copy of …

Producing Quality Barley For The Malting Industry, Haley H. Oser Dph

Doctor of Plant Health Program: Dissertations and Student Research

The University of Nebraska – Lincoln Doctor of Plant Health program requires each student to fulfill a professional internship over the last summer of the program. For my internship, I worked as a Barley Scientist Intern for MillerCoors and Golden Malting in Golden, Colorado. During this internship I gained a fundamental understanding of malting barley production with a significant emphasis on grain quality. Barley produced for malting must fulfill strict industry quality standards before it is accepted by the head maltsters. These quality standards include: a high germination rate, low moisture content, protein content within an acceptable range and the …

Signal Regulators Of Systemic Acquired Resistance, Qing-Ming Gao, Shifeng Zhu, Pradeep Kachroo, Aardra Kachroo

Plant Pathology Faculty Publications

Salicylic acid (SA) is an important phytohormone that plays a vital role in a number of physiological responses, including plant defense. The last two decades have witnessed a number of breakthroughs related to biosynthesis, transport, perception and signaling mediated by SA. These findings demonstrate that SA plays a crictical role in both local and systemic defense responses. Systemic acquired resistance (SAR) is one such SA-dependent response. SAR is a long distance signaling mechanism that provides broad spectrum and long-lasting resistance to secondary infections throughout the plant. This unique feature makes SAR a highly desirable trait in crop production. This review …