Plant Sciences Commons^™

Mechanisms For High Light Tolerance In A Fast-Growing Cyanobacterium, Patricia Walker

Arts & Sciences Electronic Theses and Dissertations

Through oxygenic photosynthesis, cyanobacteria, algae, and plants convert light into chemical energy. However, highly energetic light often damages the photosynthetic apparatus, which can lead to the decline of photosynthetic activity (photoinhibition), and prolonged photoinhibition can lead to cell death. Cyanobacteria enact various protective mechanisms to mitigate photodamage, many of which have been conserved in plants. Repair of PSII reaction centers, decreased light absorption, quenching of excess absorbed energy, and biosynthesis of antioxidants all work to mitigate damage during high light. Due to the adjustments to photosynthesis, acclimation to high light requires remodeling of cellular metabolism and physiology. Therefore, phototrophs have …

Dynamics Of Redox-Driven Molecular Processes In Local And Systemic Plant Immunity, Philip Berg

Theses and Dissertations

The work here presents two main parts. In the first part, chapters 1 – 3 focus on dynamical systems modeling in plant immunity, whereas chapters 4 – 6 describe contributions to computational modeling and analysis of proteomics and genomics data. Chapter 1 investigates dynamical and biochemical patterns of reversibly oxidized cysteines (RevOxCys) during effector-triggered immunity (ETI) in Arabidopsis, examines the regulatory patterns associated with Arabidopsis thimet oligopeptidase 1 and 2’s (TOP1 and TOP2), roles in the RevOxCys events during ETI, and analyzes the redox phenotype of the top1top2 mutant. The second chapter investigates the peptidome dynamics during ETI …

Leveraging Mass Spectrometry-Based Proteomics And Post-Translational Modifications For System-Wide Understanding Of Bioenergy Plants And Their Environment, Him K. Shrestha

Doctoral Dissertations

Bioenergy research focuses on utilizing renewable biomass feedstocks to produce biofuels and bioproducts to address growing concerns about energy security and climate change. To better understand the details of bioenergy crop production and conversion to bioproducts, it is essential to characterize bioenergy plants and their environments at a molecular systems level. Mass spectrometry has emerged as a promising technique for detailed proteomic information, including post-translational modifications (PTMs), of molecular processes and cellular functions of biological systems. In this dissertation, proteomic approaches have been optimized and implemented to deepen our understanding of the interaction of plants and their environment in a …

Spatiotemporal Transcriptome Diversity And Responses To Salinity Tolerance In The Extremophyte Schrenkiella Parvula, Chathura Wijesinghege

LSU Doctoral Dissertations

Schrenkiella parvula is an extremophyte model related to the most widely studied plant model, Arabidopsis thaliana and Brassica crops in the mustard family (Brassicaceae). It can thrive in highly saline environments where the soil is enriched in Na⁺, K⁺, Li⁺, borates, and chlorides. Understanding how this extremophyte can survive high salinity with genomic adaptations can provide insight into developing stress resilient crops in the future. Gene expression of S. parvula in response to salt has been investigated using shoot and root tissue from mature vegetative-phase plants. However, prior studies have not examined the transcript …

A Bacterial Microbiome Analysis Of Solarized Ginseng Garden Soils, Anka Colo

Undergraduate Student Research Internships Conference

American ginseng (Panax quinquefolius) is a highly valued perennial crop grown for its roots during a four-year cultivation cycle. American ginseng is subject to ginseng replant disease (GRD) in which severe root rot develops in newly planted ginseng grown in a former ginseng garden. A common strategy to mitigating GRD is not available and techniques such as fumigation, fungicides, and biocontrol are ineffective, banned, or are slowly being phased out. Alternatively, soil solarization is a pre-plant technique used to treat soil to reduce disease inoculum and alter soil microbiomes. In summer 2019, a six-week soil solarization experiment was …

Comparative Genomics And Virulence Studies Of Streptomyces Soil Rot And Scab Pathogen Species, Natasha Soares

LSU Doctoral Dissertations

Comparative genomic analyses were performed to gain insights into the organization and content of the genome of Streptomyces ipomoeae, the soil rot pathogen that infects sweetpotatoes. Unlike Streptomyces scab pathogens, the thaxtomin phytotoxin gene cluster (txt) in S. ipomoeae does not appear to reside within a genomic island and has diverged from its scab pathogen counterparts. Increased usage of the rare TTA codon, particularly for the txt cluster, suggests greater translational control by the bldA tRNA in S. ipomoeae. Orthologous gene searches and secondary metabolite profiling yielded ortholog groups and metabolite gene clusters that were exclusive …

Effect Of Cover Crops, Grazing And Tillage Practices On Soil Microbial Community Composition, Function, And Soil Health In East Central Mississippi Soybean Production System., Namita Sinha

Theses and Dissertations

Integrating crop and livestock is being considered to improve soil health by carbon sequestration. A two-year study (2019-2021) at CPBES in Newton, MS was aimed to evaluate soil microbial diversity in the warm, humid regions, specifically southeastern USA. Amplicons targeting bacterial 16S rRNA genes and fungal ITS2 regions were sequenced. Taxonomic assignment and microbial diversity characterization were performed using QIIME2^®. Soil fungal diversity showed significant differences (alpha diversity, p = 0.031 in yr. 2020 and beta diversity, p = 0.037 in yr. 2021). Canonical Correspondence Analysis (CCA) and Mantel test showed significant influence on fungal diversity due to …

Better Understanding Genomic Architecture With The Use Of Applied Statistics And Explainable Artificial Intelligence, Jonathon C. Romero

Doctoral Dissertations

With the continuous improvements in biological data collection, new techniques are needed to better understand the complex relationships in genomic and other biological data sets. Explainable Artificial Intelligence (X-AI) techniques like Iterative Random Forest (iRF) excel at finding interactions within data, such as genomic epistasis. Here, the introduction of new methods to mine for these complex interactions is shown in a variety of scenarios. The application of iRF as a method for Genomic Wide Epistasis Studies shows that the method is robust in finding interacting sets of features in synthetic data, without requiring the exponentially increasing computation time of many …

Genome Evolution In The Salicaceae: Genetic Novelty, Horizontal Gene Transfer, And Comparative Genomics, Timothy Yates

Doctoral Dissertations

Genome evolution is a powerful force which shapes genomes over time through processes like mutation, horizontal transfer, and sexual reproduction. Although questions which aim to explore genome evolution are broad, they are all understood through the discovery and comparison of genetic variation. For example, genetic diversity may explain differences in phenotypes, etiology of disease, and is essential for phylogenomic analysis. Recently, the democratization of next generation and third generation DNA sequencing technologies have allowed for genomics to produce large amounts of sequence data. This has facilitated the capture of genetic variation at species and population scales.

Populus and Salix are …

Manipulating The Root Mycobiome To Improve Plant Performance And Reduce Pathogen Pressure In Corn (Zea Mays), Noor F. Saeed Cheema

Electronic Thesis and Dissertation Repository

Crop yield often varies within a field of a single genetically uniform crop plant, with the causes presumed to be a mix of both biotic and abiotic factors. Manipulating crop root mycobiomes could potentially increase yield by reducing pathogen impacts and improving access to soil water and nutrients. This study aimed to identify different fungal inoculation treatments that could increase the growth of corn seedlings sown in low productivity soils to that in high productivity soils and shift the root mycobiome composition. Fungal inoculation treatments did not have significantly different root mycobiome composition than seedlings grown in low yield control …

Transcriptional Analysis Of Maize Under Drought Stress And The Impact Of Plant Maturity, Oliver J. Oviedo

Biology ETDs

Climate change related drought is projected to harm maize production. Water use strategies can help mitigate the impact of drought on crop yield. However, little is known about maize metabolic response to drought at different developmental stages. To shed light on this, drought conditions were applied to maize at the six-leaf stage (V6), twelve leaf stage (V12), and tassel stage (VT). V6 and VT took eight days to achieve a low stomatal conductance threshold, but V12 took 16 days. Differential gene expression analysis of the transcriptome indicates that V6 showed the most response with 53 impacted metabolic pathways, many of …

Native Soil Virus Abundance, Composition, And Mobility Under Natural And Managed Agricultural Conditions, Regan Mcdearis

Doctoral Dissertations

Soil viruses are ubiquitous in the environment and important for their influence on host community composition and function. Viral infection influences host evolution, metabolism, function, diversity, community evenness, and more. As host bacteria play critical roles in agricultural systems, including nutrient cycling and soil aggregate formation, the influence which soil viruses have on their hosts makes them key players in these systems. However, many important questions remain regarding virus abundance and distribution under human imposed and natural conditions in agricultural systems. Understanding how these conditions impact virus abundance, transport, and community structure is critical for a broader understanding of soil …

Multi-Omic Systems Biological Analysis Of Host-Microbe Interactions, Piet Jones

Doctoral Dissertations

Systems biology offers the opportunity to understand the complex mechanisms of various biological phenomena. The wealth of data that is produced, at an increasing rate, provides the potential to meet this opportunity. Here we take an applied approach to integrate multiple omic level data sources in order to generate biologically relevant hypotheses. We apply a novel analysis pipeline to model both, in concert, the microbial and transcriptomic signature from COVID-19 positive patients. We show patients may suffer from an increased microbial burden, with an increased pathogen potential. Gene expression evidence further shows patients may exhibit a compromised barrier immunity, owing …

Exploration Of Genes Controlling Grain Yield Heterosis In Hybrid Wheat (Triticum Aestivum L.) Utilizing 3ʹ Rna Sequencing, Nichole Miller

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

The implementation and future success of hybrid wheat (Triticum aestivum L.) is impacted by breeders’ inability to create consistent high yielding, high heterosis hybrids. This research addresses this problem by conducting an exploration of transcriptomes from hybrids and parent lines to determine what genes are active in heterotic or non-heterotic hybrids and how their level of expression can explain the phenotype of grain yield heterosis. Using hybrids that showed positive mid-parent heterosis (MPH), classified as heterotic in our study, and negative or no difference MPH hybrids, classified as non-heterotic, differentially expressed genes (DEGs) potentially related to heterosis and hybrid …

Microbial Diversity And Community Structure In Sediments Associated With The Seagrass (Thallassia Testudinum) In Apalachicola Bay, Florida, Rahma Ahmed, Thomas Mcelroy, Troy Mutchler

Symposium of Student Scholars

Seagrass is an angiosperm which provides many ecosystem services in coastal areas, such as providing food, shelter and nurseries for many species, and decreasing the impact of waves on shorelines. A global assessment reported that 29% of known seagrass meadows are in a state of decline due to the effects of human activity. Seagrass is commonly found in shallow marine waters where they form meadows containing a microbiome that plays an important role in providing nutrients for seagrass growth, though little is known about the microorganisms within the seagrass meadow sediments. Our project collected sediments from seagrass meadows and adjacent …

Genetic Characterization Of Resistance To Bacterial Panicle Blight And Sheath Blight In Rice Using Qtl Linkage Analysis And Qtl-Seq, John Christian E. Ontoy

LSU Master's Theses

Bacterial panicle blight (BPB) and sheath blight (SB) are major diseases of rice causing significant yield reduction in conducive conditions. Few cultivars have shown reliable resistance to these diseases. In this study, a recombinant inbred line (RIL) population derived from the U.S. cultivars Jupiter (moderately resistant) and Trenasse (susceptible) was investigated to identify genomic regions associated with BPB and SB resistance. Phenotypes in BPB and SB, as well as days to heading (DH), of the RIL population were evaluated in the field. DH was found to be correlated to BPB and SB diseases. BPB was also positively correlated to SB. …

Phylogenomic Discordance Suggests Polytomies Along The Backbone Of The Large Genus Solanum, Edeline Gagnon, Rebeccca Hilgenhof, Andrés Orejuela, Angela J. Mcdonnell, Gaurav Sablok, Xavier Aubriot, Leandro Giacomin, Yuri Gouvêa, Thamyris Bragionis, João Renato Stehmann, Lynn Bohs, Steven Dodsworth, Christopher T. Martine, Péter Poczai, Sandra Knapp, Tiina Särkinen

Faculty Journal Articles

Premise of the study

Evolutionary studies require solid phylogenetic frameworks, but increased volumes of phylogenomic data have revealed incongruent topologies among gene trees in many organisms both between and within genomes. Some of these incongruences indicate polytomies that may remain impossible to resolve. Here we investigate the degree of gene-tree discordance in Solanum, one of the largest flowering plant genera that includes the cultivated potato, tomato, and eggplant, as well as 24 minor crop plants.

Methods

A densely sampled species-level phylogeny of Solanum is built using unpublished and publicly available Sanger sequences comprising 60% of all accepted species (742 spp.) …

Community Assembly And Stress Response Of Grassland Phyllosphere Bacteria, Emily Bechtold

Doctoral Dissertations

Grasslands are an important ecosystem with potential to help stabilize food security and reduce greenhouse gas levels. As global temperatures rise, weather patterns are predicted to drastically change. The resulting increase in intensity, duration, and frequency of drought in important grassland areas will not only affect agricultural production, but also increase grassland susceptibility to fire, disease, and soil erosion. Thus, developing ways to sustainably promote grassland health and production is essential to increase food security and reduce environmental strain. Microbes in the phyllosphere, or aerial surface of plants, promote host fitness through phytohormone and nutrient production, increased stress tolerance, and …

Chromomap: An R Package For Interactive Visualization Of Multi-Omics Data And Annotation Of Chromosomes, Lakshay Anand, Carlos M. Rodriguez Lopez

Horticulture Faculty Publications

BACKGROUND: The recent advancements in high-throughput sequencing have resulted in the availability of annotated genomes, as well as of multi-omics data for many living organisms. This has increased the need for graphic tools that allow the concurrent visualization of genomes and feature-associated multi-omics data on single publication-ready plots.

RESULTS: We present chromoMap, an R package, developed for the construction of interactive visualizations of chromosomes/chromosomal regions, mapping of any chromosomal feature with known coordinates (i.e., protein coding genes, transposable elements, non-coding RNAs, microsatellites, etc.), and chromosomal regional characteristics (i.e. genomic feature density, gene expression, DNA methylation, chromatin modifications, etc.) of organisms …

Development Of Genomic Resources In Vitis Riparia For Discoveries On Pre- And Post-Transcriptional Molecular Regulators Of Early Induction Into Endodormancy, Michael Robben

Electronic Theses and Dissertations

Grapevine is one of the most important fruit crops in the world, responsible for billions in global sales annually. The largest threat to grapevine and other crop production is global climate change resulting human activities. This brings unpredictable and drastic changes in ambient air temperatures to many climates in which grapes are grown. Lower temperatures and inclement weather are already responsible for millions in lost revenue due to tissue damage of established plants. Thus, protecting grapevine crops from weather-related damage is the biggest concern to growers aside from pathogen- and diseaserelated crop damage. The primary mechanism for winter survival in …

Characterizing Drought Adaptations, Phenotypic Plasticity, And Fixed Gene Expression Patterns Within Quercus, James K. Rauschendorfer

Dissertations, Master's Theses and Master's Reports

This dissertation was written on topics related to the genus Quercus with a primary focus on Quercus ellipsoidalis (northern pin oak) and Quercus rubra (northern red oak). Within this dissertation are chapters related to the setup of experimental common gardens within the Ford and Kellogg experimental forest, a literature review describing drought adaptations of Quercus sect. Lobatae (red oak group), identification of transcription factors within the Q. robur (English oak) and Q. rubra genomes, a study comparing leaf trait phenotypic plasticity of Q. ellipsoidalis and Q. rubra, and an RNA-seq experiment studying ecological speciation between Q. ellipsoidalis and Q. …

Getting To The Root Cause: The Genetic Underpinnings Of Root System Architecture And Rhizodeposition In Sorghum, Farren Smith

Graduate Theses, Dissertations, and Problem Reports

Plants are some of the most diverse organisms on earth, consisting of more than 350,000 different species. To understand the underlying processes that contributed to plant diversification, it is fundamental to identify the genetic and genomic components that facilitated various adaptations over evolutionary history. Most studies to date have focused on the underlying controls of above-ground traits such as grain and vegetation; however, little is known about the “hidden half” of plants. Root systems comprise half of the total plant structure and provide vital functions such as anchorage, resource acquisition, and storage of energy reserves. The execution of these key …

Cbp60-Db: An Alphafold-Predicted Plant Kingdom-Wide Database Of The Calmodulin-Binding Protein 60 (Cbp60) Protein Family With A Novel Structural Clustering Algorithm, Keaun Amani, Vanessa Shivnauth, Christian Castroverde

Biology Faculty Publications

Molecular genetic analyses in the model species Arabidopsis thaliana have demonstrated the major roles of different CAM-BINDING PROTEIN 60 (CBP60) proteins in growth, stress signaling, and immune responses. Prominently, CBP60g and SARD1 are paralogous CBP60 transcription factors that regulate numerous components of the immune system, such as cell surface and intracellular immune receptors, MAP kinases, WRKY transcription factors, and biosynthetic enzymes for immunity-activating metabolites salicylic acid (SA) and N-hydroxypipecolic acid (NHP). However, their function, regulation and diversification in most species remain unclear. Here we have created CBP60-DB, a structural and bioinformatic database that comprehensively characterized 1052 CBP60 gene homologs …