Doctor of Philosophy (PhD), Ohio University, 2024, Plant Biology (Arts and Sciences)

Plants encounter various biotic and abiotic stresses daily and have developed defense mechanisms to overcome these challenges. One key system involved in these defense mechanisms is the ubiquitin (Ub)-26S proteasome system (UPS), which targets malfunctioning proteins for degradation through Ub-tagged proteasomal pathways. The E3 ligases, specifically S-phase kinase-associated protein 1 (SKP1), Cullin 1 (CUL1), and F-box (SCF) complexes, play crucial roles in this process by recognizing and tagging specific protein substrates. Arabidopsis thaliana, with over 700 F-box proteins, has the largest group of E3 ligases, yet only 5% have been functionally characterized. Phylogenetic relationships among 111 plant species have identified four clusters of F-box genes, including a cluster with more conserved F-boxes, referred to as core Arabidopsis F-box (CAF) genes. Given that CAF genes have more known functions compared to other clusters, this dissertation hypothesizes significant potential for discovering new functions among the uncharacterized F-boxes within this group. Considering the evolutionary conservation of most CAFs, I adopted a genetic approach to investigate the roles of CAFs during seed germination and seed development. To address the challenges posed by functional redundancy of duplicated CAF genes and the lethality associated with constitutive F-box overexpression in transgenic plants, I created a library of inducible overexpression lines for 40 CAF genes, many of which lacked known biological functions. By systematically examining the effects of conditional overexpression of these 40 CAFs, I found that CAF overexpression during seed germination and seed development can positively or negatively regulate radicle rupture growth, thus controlling the germination process. Specifically, I identified 24 CAFs that enhance radicle rupture and two that inhibited it by interfering with abscisic acid (ABA)-mediated germination suppression. Induction of CAFs during seed (open full item for complete abstract)

Master of Science, Miami University, 2024, Biology

Recent studies show root trait plasticity within species, suggesting differences in root response to ecosystem heterogeneity. The multi-axis root economic spectrum framework (RES) proposes that most root trait variation is explained by phylogeny and ecosystem conditions. We evaluated architecture and morphology in tree species in a long term, nitrogen (N) x phosphorus (P) fertilization study. Root traits differed between taxa and responded to nutrient addition. Red maple roots were less branched, produced fewer tips, and were thicker than roots of the species beech and birch. In both taxa, branching density, total root tips, average diameter, and the root length fraction in the 0-0.25 mm diameter class were lower in response to P. Most of these effects were reversed in response to N+P. Our findings show these species shift root growth to acquisitive traits when P limitations is alleviated but become conservative in response to N+P. This highlights the need to consider whether root growth is single or co-limited in ecosystems due to different effects of N x P interaction on root traits. We must continue refining the multi-axis RES framework to better account for within species plasticity in response to ecosystem conditions.

Bachelor of Science (BS), Ohio University, 2024, Environmental and Plant Biology

Caryophyllaceae flowers have a wide range of morphological appearances, particularly in regards to their stamens and petaloids. In order to determine how these structures evolved, I reviewed the phylogenetic relationships, mature morphology, and developmental pathways of flowers in the family. I concluded that in addition to an antesepalous whorl of stamens, there was likely a whorl of some ancestral structure in the alternisepalous position. This structure may have been a petal, a stamen, or a transitionary staminode, but it diversified in various lineages into the numerous forms we see today.

Bachelor of Science (BS), Ohio University, 2024, Environmental and Plant Biology

A plant's survival is largely impacted by its ability to sense and respond to gravitational changes, such as the changes that occur in spaceflight. However, the gravitropic signaling pathway is not fully understood. In the BRIC-20 experiment aboard the International Space Station, the Arabidopsis proton pump AHA2 was found to be differentially phosphorylated in microgravity compared to ground controls. AHA2 is hypothesized to be involved between plant hormone movement and differential growth during gravity signaling. When subject to reorientation, aha2 mutant seedlings had increased root curvature compared to wild type. Furthermore, wild type seedlings treated with fusicoccin, a phytotoxin that increases AHA2 phosphorylation and activity, had increased root curvature compared to untreated plants. To determine the role of AHA2 phosphorylation in gravitropic signaling, several lines of transgenic Arabidopsis with modifications in phosphorylation sites are being developed. The transformants will then be phenotyped for altered gravity response, showing if the phosphorylation of the AHA2 protein is involved in a plant's gravity response. These findings will further knowledge on the molecular mechanisms of gravitropism to develop space-tolerant plants for life support in spaceflight and for habitation of the moon, Mars, and beyond.

Doctor of Philosophy, The Ohio State University, 2024, Translational Plant Sciences

Grapevine (Vitis) is the world's most valuable fruit crop, therefore, reducing yield losses to stressors is paramount. Vitis labrusca, a wild North American grapevine, is well adapted to its local environment, exhibiting stout pathogen resistance. Meanwhile, Vitis vinifera grapevine, grown worldwide for winemaking, is native to Europe and is highly susceptible to biotic stressors, particularly fungal and insect pests. V. labrusca has been long utilized in Vitis breeding programs to imbue resistance. Therefore, in this dissertation, we determined if V. labrusca acc. ‘GREM4' was more insect herbivory resistant than V. vinifera cv. ‘PN40024' and investigated the morphological, genetic, and metabolomic factors which may contribute to resistance. In an herbivory choice assay, Japanese beetles (Popillia japonica), a major pest of grapevine, preferred to feed upon ‘PN40024' compared to ‘GREM4'. Further, increased leaf area was consumed on ‘PN40024' compared to ‘GREM4' in a time course (30min, 1h, and 4h) feeding assay. These results reported ‘GREM4' is resistant to Japanese beetle herbivory compared to ‘PN40024'. To determine morphological adaptations that may impact defense, trichomes were next investigated. Trichome densities were greater on ‘GREM4' compared to ‘PN40024' leaves. In trichome-focused herbivory studies, beetles exhibited a preference for lower trichome density sides of leaves and, when provided tissues with equal trichome densities for both ‘GREM4' and ‘PN40024', more leaf tissue was still lost from ‘PN40024' compared to ‘GREM4'. These results report that trichomes play a role in resistance but are not the sole factor. Therefore, we conducted a comparative transcriptomic analysis to identify differences in gene expression upon insect herbivory between the two species. When comparing constitutive expression differences prior to insect herbivory, genes with greater expression in ‘GREM4' were enriched in secondary metabolite biosynthesis while enr (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Translational Plant Sciences

Field pennycress (Thlaspi arvense L.) is a winter annual with extreme cold hardiness and seed oil properties desirable for sustainable aviation fuel production. Integration of pennycress as an off-season biofuel cash crop into Midwest corn and soybean rotations could lead to the production of 1 billion liters of seed oil annually, therefore boosting farmer revenue and offsetting carbon emissions. Pennycress fields are vulnerable to heavy spring precipitation events, which can lead to waterlogged soils where the root system is submerged under water. However, it is unknown if growth, development, or yield of pennycress is affected by waterlogging at the reproductive developmental stage which occurs during April. This work aimed to characterize the morphological and transcriptomic responses of pennycress under one week of waterlogging during the reproductive stage. This was done with two core pennycress lines: one is the reference genome (MN106), and one is commonly used for gene editing (SP32-10). Additionally, natural populations of pennycress with predicted variation in soil water availability were included. One week of waterlogging at the reproductive stage under controlled conditions significantly reduced total seed weight in seven accessions, including SP32-10, whereas three accessions did not have reduced seed weight, such as MN106. Therefore, natural phenotypic variation in waterlogging responses existed between the two core lines, so they were further investigated to determine the transcriptomic responses contributing to waterlogging tolerance. Twice as many genes were differentially expressed between waterlogged and control roots in MN106 (3,424 genes) compared to SP32-10 (1,767 genes) after one week of waterlogging at the reproductive stage. Functional enrichment analysis of upregulated differentially expressed genes in both lines revealed Gene Ontology (GO) terms associated with hypoxia and decreased oxygen, including genes involved in alcoholic fermentatio (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Plant Biology (Arts and Sciences)

Transcription factors involved in regulating plant cell wall biosynthesis are diverse and come from various families, including but not limited to AP2/ERF, MYB, NAC, bZIP, and WRKY. These TFs play crucial roles in modulating the expression of genes responsible for cell wall synthesis, composition, and structure, thereby influencing plant development and responses to environmental stimuli. Using gene association networks (GAN) analysis, four transcription factors co-expressed with cellulose synthases and glycosyltransferases for xylan biosynthesis were identified, namely, Os06g0194000 (OsERF071), Os02g0782700 (OsERF070), Os09g0434500 (OsERF072) from the AP2-ERF family, and Os08g0549000 (OsMYB102) from the MYB family. Loss-of-function allelic mutants were created using CRISPR/Cas9 technology. Allelic mutants that are homozygous and Cas9-free were evaluated morphologically, physiologically, and biochemically in the T2 generation. Mutants in Os06g0194000 (OsERF071) exhibited the most significant alterations compared to the CRISPR control plants, prompting the generation of overexpression lines for this gene to enable a more comprehensive functional analysis of this gene. Mutants lacking OSERF071 were taller plants with larger seed sizes, panicle lengths, thousand grain weights, biological yields, and grain yields compared to the CRISPR control plants, while the opposite phenotypes were observed in overexpression lines. Additionally, the allelic mutants exhibited higher content of lignin in their tissues compared to the control and showed higher expression levels of the OsCesA genes related to secondary cell wall biosynthesis compared to those linked to primary cell wall biosynthesis, suggesting OsERF071 may function as a repressor of lignin biosynthesis during primary cell wall deposition. Taken together, my results suggest that OsERF071 may function as a repressor of secondary cell wall formation in tissues that are dividing and growing. Another gene of interest wa (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Plant Biology (Arts and Sciences)

Heteroxylans (HXs) are major hemicellulosic polymers, that provide structural integrity of plant cell walls which directly impact the growth and development of the plant. The backbone of HXs is comprised of β-linked xylose (Xyl) residues with different substitution patterns (acetyl, glucuronic acid/methylglucuronic acid [GlcA/[Me]GlcA] and/or arabinofuranosyl [Ara] side chains). In Arabidopsis, glucuronidation of HXs is mediated by GlucUronic acid substitution of Xylan (GUX) enzymes which are members of the GT8 family (CAZy). Reduced GlcA/[Me]GlcA side chains in HXs have been found to improve saccharification by reducing biomass recalcitrance and improving biofuel production. Therefore, identifying GUXs is of importance, offering insights into enhancing biofuel production and ensuring agricultural sustainability. Recently, GUXs have been identified in other species like conifers, Brachypodium and sugarcane. However, several outstanding questions about HX glucuronidation in grasses remain unanswered. Thus, this work focuses on the understanding of HX glucuronidation in rice, a significant cereal crop renowned for its nutritional value and substantial biomass, holding great potential for biofuel conversion and food security challenges. Through comprehensive phylogenetic and bioinformatics analyses, I identified three OsGUXs in rice, designated as OsGUX-A, OsGUX-B, and OsGUX-C. These OsGUX proteins exhibited structural conservation with counterparts from various species and harbored specific motifs and domains characteristic of GUX enzymes. Subcellular localization studies confirmed their presence within the Golgi apparatus, consistent with the site of HX biosynthesis. Using in vitro assays, I demonstrated that these OsGUXs have glucuronosyltransferase activity and exclusively utilize UDP-GlcA as a substrate. Further investigation through genetic complementation of Arabidopsis gux1/2/3 mutants, characterized by HX lacking GlcA/[Me]GlcA side chains, indicated that OsG (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Plant Biology (Arts and Sciences)

Protein degradation through the Ubiquitin (Ub)-26S Proteasome System (UPS) is a major gene expression regulatory pathway in plants. In this pathway, the 76-amino acid Ub proteins are covalently linked onto a large array of UPS substrates with the help of three enzymes (E1 activating, E2 conjugating and E3 ligating enzymes) and direct them for turnover in the 26S proteasome complex or through autophagy-mediated degradation. The S-Phase Kinase-Associated Protein 1 (Skp1), cullin (CUL)1, and F-box (FBX) protein (SCF) complexes have been identified as the largest E3 ligase group in plants. Since the FBX proteins recognize and determine the specificity of SCF substrates, much effort has made to characterize their genomic, physiological, and biochemical roles in the past two decades of functional genomic studies. The co-immunoprecipitation failed to capture transient interaction while the yeast two-hybrid only test protein interaction in yeast cell instead of plant tissue. Therefore, the sheer number and high sequence diversity of the FBX gene family demands new approaches to uncover unknown functions. In this research, first, from the proteomic level, I developed and tested a proximity labeling and co-immunoprecipitation approach for determining the proteome of active FBX proteins and their associated complexes in Arabidopsis. We demonstrate that ASK1-TurboID is not fully functioning, which led us to discover a novel antagonism between biotinylation and ubiquitylation in regulating protein stability in vivo. This discovery lowers the effectiveness of proximity labeling in ubiquitylation studies. Second, from the FBX level, I characterized a new FBX protein that is involved in reproductive development. The mutant was created using CRISPR/Cas9. And it was confirmed that mutation of this FBX gene impacted seed development. The potential substrates were identified and confirmed using yeast two-hybrid and split-luciferase assay. Third, from the substrate (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2024, Molecular and Cellular Biology (Arts and Sciences)

Functional studies of the ubiquitin (Ub)-26S proteasome system (UPS) have demonstrated that virtually all aspects of the plant's life involve UPS-mediated turnover of abnormal or short-lived proteins. However, developmental characterization of the UPS, including in seeds and fruits, remains scarce. Unfortunately, early termination of embryogenesis limits the scope for characterizing the UPS activities in reproductive organs. In this dissertation, I utilized a biochemical approach to tackle the developmental role of UPS in plants, using Arabidopsis thaliana (Arabidopsis hereafter) as a model. The overarching goal of my research is to unravel the molecular mechanisms of UPS underpinning seed development so that new molecular breeding technologies could be developed to promote seed production. First, I systematically compared expression changes of multiple 26S proteasome subunits along with the dynamics of proteasome activity and total protein ubiquitylation in seedlings and developing siliques of Arabidopsis. Because autophagy plays the second largest role in maintaining proteome stability, I parallelly studied three late-limiting enzymes that are involved in autophagy influx. My experiments unexpectedly discovered that, in opposite to the activities in seedlings, both protein and transcript levels of six selected 26S proteasome subunits gradually decline in immature siliques toward maturation while the autophagy influx rises, albeit in a nutrient-rich condition. I also discovered a reciprocal turnover pathway between the proteasome and autophagy. While the autophagy influx is suppressed in seedlings by UPS-mediated degradation of its three key enzymes, transcriptional reprogramming dampens this process in siliques that in turn stimulates a bulk autophagy degradation of proteasomes. Collectively, my discovery about the developmental changes of the UPS and autophagy activities suggests that they relay the proteome homeostasis regulation in early seed development, w (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Plant Pathology

Phytophthora root and stem rot is one of the top ten most yield-limiting soybean [Glycine max (L.) Merr] diseases in the U.S. and Canada. The causal agent of this disease, Phytophthora sojae (Kaufmann & Gerdemann), is an oomycete (water mold) organism that is often managed by using disease-resistant soybean cultivars containing a single Rps gene to a specific pathotype of the pathogen combined with quantitative disease resistance (QDR). Due to the limitation of the number of effective Rps genes available, as the populations of this pathogen have adapted to these genes, it is a necessity to find new Rps genes and identify perfect markers for QDR genes, which have a smaller effect but can resist all pathotypes of P. sojae, that can be used in the development of modern soybean cultivars. In this dissertation, the main approach for all three chapters is to examine the mechanisms of disease resistance in soybeans towards P. sojae using different forward and reverse genetic approaches. A previous study found more than 100 candidate genes by mapping the expression quantitative disease-resistance loci (eQDRL) from the Conrad × Sloan population. To explore and validate the functions of these genes, a fast neutron (FN) population from the University of Minnesota, derived from soybean cultivar M92-220, with these genes deleted was employed. Thus, the first chapter's first objective was to compare cultivars M92-220 and Conrad at phenotypic and transcriptomic levels for their QDR resistance to determine if the molecular mechanisms associated with the eQDRLs were similar to those previously found in Conrad. Then, the next objective was to explore how the loss of the candidate genes using mutants that were highly susceptible would affect the soybean resistance response following inoculation with P. sojae by examining the three most susceptible FN mutants. Conrad and M92-220 were found to share high levels of QDR in the phenotypic assay as well as having several similar defense-r (open full item for complete abstract)

Master of Science, The Ohio State University, 2023, Evolution, Ecology and Organismal Biology

Invasive temperate lianas are ecologically impactful and increasing in abundance in North America, but information regarding their ecophysiology is relatively scarce. I selected four introduced species representing potentially contrasting shade strategies, "light-demanding" Ampelopsis brevipedunculata and Celastrus orbiculatus and shade-tolerant Hedera helix and Euonymus fortunei, to compare their responses to either neutral shade or shade with a reduced R:FR ratio of 0.88 from the ambient 1.3, with the reduced-R:FR shade intended to more closely resemble canopy shade and induce a phytochrome-mediated shade avoidance response. I tested whether responses differed by species and by light quality, measuring five morphological and physical traits in all species and four photosynthetic traits in the shade-tolerant species. Mortality in shaded Ampelopsis was high along with Celastrus in all conditions, while no mortality was observed in shade-tolerant species. Differential responses to light quality were detected in three morphological traits and one photosynthetic parameter. Relative to neutral shade, leaf mass as a proportion of total aboveground biomass increased in Ampelopsis and Celastrus in reduced R:FR shade while increasing in both treatments for shade-adapted species. Internode length was only greater in R:FR-reduced shade than neutral shade for Celastrus, with no difference in elongation detected between shade treatments in any other species. These changes in allocation patterns and gross morphology were limited to the light-demanding species. While internode length was greatest for all species in control conditions, a subsequent analysis of biomass-adjusted internode length indicated that internodes were longest in the shade treatments, and nonsignificantly longer in R:FR-reduced shade relative to neutral shade. Hedera biomass was greater in R:FR-reduced shade, increasing nonsignificantly in all other species. Quantum yield (φ) was greatest in Hedera but unaffe (open full item for complete abstract)

MS, Kent State University, 2023, College of Arts and Sciences / Department of Biological Sciences

Eastern redcedar (Juniperus virginiana L. var. virginiana) is a native species currently invading open areas and grasslands outside of its original range in the United States. I studied the eastern redcedar's (ERC) invasion patterns in the Lakeside Daisy State Nature Preserve (LDSNP), a short grass prairie located on the Marblehead Peninsula in Ohio, examining the changes in the genetic diversity and structure of the encroaching population. I investigated the relative importance of long-distance dispersal vs. diffusion in the invasion of this short grass prairie by ERC. I used eight microsatellite marker loci and a database of single nucleotide polymorphisms to infer gene flow from external sources vs. within-population recruitment. I found that the older trees in this preserve were less than fifty-years-old, indicating that the population was established between 1970 and 1980. When I grouped trees into five age categories of 10-year increments, we found that the allelic diversity, as indicated by the average number of alleles per locus, increased as the age of the trees decreased. Principal Coordinate Analysis showed two distinct groups of trees in the LDSNP that I investigated further using soil type. Analysis of the population structure of the ERC trees using ADMIXTURE revealed three ancestral clusters in the ERC populations. All ancestral clusters are present in all age groups, suggesting that there is continual input of genetic information from the ancestral clusters. Overall, my findings indicate that ERC encroachment of the LDSNP results from multiple and reiterated gene flow events from the edge of the range through animal-mediated seed dispersal at short and intermediate distances.

Doctor of Philosophy, The Ohio State University, 2023, Plant Pathology

Plants exist in a constantly evolving microbial environment that significantly influences their growth, development, and overall well-being. Within this microbial milieu, certain bacteria play a pivotal role in enhancing plant health and growth. These beneficial bacteria are collectively referred to as plant growth-promoting bacteria (PGPB). They offer valuable services to plants, including improved nutrient absorption, heightened growth stimulation, and increased resilience against pathogens and the other environmental adversities. PGPB engage with plants through diverse modes of interaction, such as root colonization, endophytic association, or rhizosphere competence. An in-depth comprehension of the molecular mechanisms and ecological dynamics governing these interactions is essential for unlocking the potential of PGPB in promoting sustainable agriculture and environmental remediation. In Chapter 1, I provide an overview of current methods used to detect and diagnose Pseudomonas syringae. This encompasses traditional approaches like culture isolation and microscopy, as well as modern techniques such as PCR and ELISA. Furthermore, I explore the upcoming advancements in this domain, emphasizing the necessity for highly sensitive and specific methods to detect pathogens even at low concentrations. Additionally, I delve into approaches for diagnosing P. syringae infections when they coexist with other pathogens. Chapter 1 Figures can be found in Appendix A. In Chapter 2, I present a significant protocol for monitoring the progression of gray mold fungal infection at various developmental stages of strawberries. I detail three distinct in vivo inoculation methods for Botrytis cinerea on strawberry plants, focusing on early, middle, and late stages of strawberry growth. Chapter 2 Figures can be found in Appendix B. In Chapter 3, I introduce Bacillus proteolyticus OSUB18 as a novel inducer of ISR (Induced Systemic Resistance). This bacterium enhances plants' r (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2023, Chemistry and Biochemistry (Arts and Sciences)

Plants represent a fascinating group of organisms that have adapted to survive in diverse environments and provide us with essential resources such as biomass, food, oxygen, and medicines. Despite significant advances in plant biology, many of their biological processes remain a mystery. One area of particular interest is plant cell wall development. Plants form cell walls in two phases: primary cell wall (PCW) and secondary cell wall (SCW). While some factors contributing to SCW development, such as hormones and transcription, are well understood, post-transcriptional regulation remains elusive. Here, I have investigated small RNAs (sRNAs) as post-transcriptional regulators in cell wall development, thus contributing to a better understanding of their underlying mechanisms. I used an inducible system to mimic SCW development and identify differentially expressed sRNAs during SCW development. My research utilized Arabidopsis thaliana (a model plant), which was optimized for this study. I followed a rigorous workflow to identify differentially expressed sRNAs. A parallel approach using data collected online to identify differentially expressed sRNAs analysis was performed. My research sheds light on the complex processes involved in plant cell wall development, specifically the role of sRNA as a post-transcriptional regulator.

Master of Science (MS), Ohio University, 2023, Molecular and Cellular Biology (Arts and Sciences)

Gravity is among the most critical of environmental cues in shaping plant growth; however, its ubiquity on Earth limits available options in the study of the plant gravity response. NASA has circumvented this obstacle by hosting experiments in the microgravity environment of the International Space Station (ISS). Gene expression data gleaned from RNA-seq and microarray analyses of Arabidopsis seedlings grown aboard the ISS has provided a wealth of information regarding how plants respond to this unique gravity condition. A meta-analysis of these datasets intersected with one of terrestrial plants exposed to an alternate gravity stimulus - a new gravity vector – has identified several novel components in the gravity signaling pathway. Of particular interest in the analysis were transcription factors, for their role in regulating downstream expression patterns. Two transcription factors were identified at this fundamental level of the Arabidopsis gravity response: ERF104, which is upregulated on earth in response to a new gravity vector and downregulated in microgravity, and IQD21, which displays the inverse expression pattern. A third gene, CIB1, was shown to be upregulated in both scenarios. Phenotypic characterizations of mutant lines of each of these genes show significant gravity sensitivity in the root tip and/or inflorescence stem, confirming their gravitropic role. Fusion constructs of these transcription factors joining each with a Human Influenza Hemagglutinin (HA) tag were generated, placed under the control of a constitutive promoter, and expressed in each gene's respective Arabidopsis T-DNA mutant line. These lines are enabling chromatin immunoprecipitation followed by sequencing (ChIP-seq) to identify binding sites of each transcription factor in the Arabidopsis genome, and consequently to infer their downstream targets. This work was done in tandem with qPCR analyses targeting the expression patterns of each protein in response to (open full item for complete abstract)

Master of Science (MS), Ohio University, 2023, Plant Biology (Arts and Sciences)

Masting is defined as highly synchronized seed production within a population that varies in intensity among years. Reproductive output of masting species and the occurrence of years with high seed production are thought to be influenced by climate and resource availability. In oaks, spring weather seems to be particularly influential to seed production. However, there is also significant variation in seed production among individuals in the same population. The goal of this study was to examine if individual variation in seed production of Quercus montana (chestnut oak) was explained by differences in pollen availability. Phenological synchrony and conspecific density were examined as indicators of pollen availability. I also asked if these variables were influenced by differences in microclimate related to topography and spring weather. The study included 36 Q. montana individuals from populations in Vinton Furnace Experimental Forest and Zaleski State Forest in southeastern Ohio. For each individual, microclimate was quantified by collecting data on elevation, slope, aspect, air temperature, soil temperature, and humidity during spring of 2022 and 2023. Observations on individual flower development were made from March to May of 2022 and 2023, and relative density of conspecifics within 50 m was also quantified. Results showed that individuals at higher elevations and on more south-facing slopes experienced warmer and drier microclimate conditions during spring, but these conditions did not significantly influence phenological synchrony in either year. Based on seed production data from 2022, there was not a significant relationship between either phenological synchrony nor conspecific density and individual seed production, however there was a significant positive relationship between individual dry weight of collected catkins and number of acorns produced. Analysis of long-term seed production collected since 2000 also revealed a positive relationship between e (open full item for complete abstract)

Doctor of Philosophy (PhD), Ohio University, 2023, Plant Biology (Arts and Sciences)

Glycosyltransferases (GTs) are important proteins that are widely distributed in both prokaryotes and eukaryotes and play a crucial role in the biosynthesis of carbohydrates and glycoconjugates. They catalyze the formation of specific glycosidic linkages by transferring sugar moieties from activated sugars to a variety of biomolecules such as carbohydrates, lipids, proteins, or water. Progress in functional genomics technologies, such as DNA sequencing and proteomics, has allowed the identification of a large number of GT genes in several species. In general, functional genomics approaches, which include genomics, genetics, proteomics, and biochemistry, are used to determine the function of a gene (i.e., GTs). In biochemical approaches, the most direct way to assign a function to a gene is through direct testing of the enzyme activity of its product (carbohydrate) in vitro. However, in contrast to genomics/proteomics approaches, the biochemical approaches are the most difficult to adapt to high-throughput screening. The reason is that biochemical approaches require the use of isolated/purified proteins, which is labor-intensive and prone to the formation of undesired products resulting from background enzyme activity. Therefore, there is a need for the development of protein-based in vitro high-throughput platforms for determination of biochemical functions of proteins, including GTs, and their interactions with other proteins. To be advantageous, a protein-based high-throughput platform should have the following characteristics: i) the platform can be adapted to all GTs and synthases, ii) the detection method should be sensitive enough to demonstrate the formation of GT products, and iii) the platform should be simple and easy to implement or accessible to any laboratory. This work describes the development of a novel platform for screening of enzyme activities of GTs in vitro. It is called the in vitro GT-array (i-GTray) platform. This platform uses an in vitro ce (open full item for complete abstract)

Master of Science in Biological Sciences, Youngstown State University, 2023, Department of Biological Sciences and Chemistry

Since the discovery of the emerald ash borer (Agrilus planipennis, Coleoptera: Buprestidae) in 2002, it has caused near 100% mortality of North American ash trees (genus Fraxinus). Moreover, uncertainties remain regarding the future of the forest regeneration dynamics after the introduction this prolific forest pathogen. The objectives of this study were to: 1) Assess regeneration potential of green ash (Fraxinus pennsylavnica Marsh.) on the Lake Erie and Lake Tonawanda plains in Western New York State where it was formerly one of the dominant trees; 2) Identify other native tree species that could repopulate depleted ash stands; and 3) Assess factors constraining regeneration like invasive shrub cover and deer browsing pressure. In 32 plots (400 – 3600 m2), proportion of ash trees in c. 2010 pre-ash-borer stands was catalogued (including dead or fallen stems), and all ash trees were assigned into health categories ranging from dead to unimpacted. Stump sprout and seedling recruits were recorded. Canopy and understory stems of all other trees were identified and measured (diameter at breast height). Identity and coverage of invasive shrubs were recorded. Data were analyzed and interpreted along gradients in two important independent variables: 1) stand age at ash borer invasion (from increment counts of fallen dead ash trees, or estimated from aerial imagery), and 2) % of ash in pre-ash-borer stands. Most adult ashes within plots were dead, and with no association with stand age or pre-ash-borer ash dominance. However, 11% of ash trees were completely un-impacted, but were <5 cm diameter and concentrated in young (<60 y) ash-dominated (>80%) stands. Stump sprouting was present in 78% of plots, and ash seedlings were noted at most sites, again primarily in young ash-dominated stands. Red and/or silver maples and American elms were the most common native trees and were most important in older less ash-dominated stands. Unfortunately, invasive shrubs were often very a (open full item for complete abstract)

Master of Science (MS), Ohio University, 2023, Plant Biology (Arts and Sciences)

A green roof provides different benefits in an urban environment, like habitat, stormwater management, reduced energy usage, aesthetic values, and carbon storage. To understand the carbon storage capacity of green roofs, it is important to understand the amount of CO2 released (efflux) and taken up by the green roof. So, I measured and compared the above and belowground biomass, soil CO2 efflux (respiration), and associated soil parameters between the green roof and the prairie site to understand how environmental variables like soil temperature and moisture on the green roof influence CO2 efflux. The green roof substrate was significantly warmer than the prairie soil, and CO2 efflux from the green roof was less sensitive to temperature (i.e., had lower Q10) than the prairie site. I hypothesize that the porosity of the green roof substrate, which accounts for its lower water-holding capacity and volumetric moisture content, lowered the potential evapotranspiration and caused higher temperature and greater variation in temperature on the green roof. The green roof also had comparatively higher variation in substrate temperature, consistent with greater variation in CO2 efflux. The differences in the plant activity led to the major differences in the CO2 efflux between the green roof and the prairie site. Higher above and belowground (root biomass) on the prairie site led to higher total CO2 efflux on the prairie site as higher aboveground biomass can lead to increased photosynthates for the roots and higher root exudates along with the higher litter input, all of which can increase autotrophic and heterotrophic respiration. However, after accounting for the differences in root biomass on soil CO2 efflux (i.e., dividing efflux by root biomass), the green roof had higher efflux than the prairie sites, indicating a higher contribution of heterotrophic sources to CO2 efflux at the green roof. Since the green roof at Schoonover Center is unique due to its location, clima (open full item for complete abstract)