Life Sciences Commons^™

Calmodulin Like 38 Is Required For Autophagy Of Hypoxia-Induced Cytoplasmic Rna Granules In Arabidopsis Thaliana, Sterling Field

Doctoral Dissertations

In response to the energy crisis resulting from submergence stress and hypoxia, the model plant Arabidopsis thaliana limits non-essential mRNA translation, and accumulates cytosolic stress granules. Stress granules are phase-separated mRNA-protein particles that partition transcripts for various fates: storage, degradation, or return to translation after stress alleviation. Another response by the plant cell to low oxygen stress is the induction of the turnover pathway autophagy. Stress granule regulation by autophagy occurs by a ‘granulophagy’ pathway in yeast and mammalian systems through which parts or whole stress granules are degraded. Whether this occurs in plants has not been investigated.

A connection …

A Systematic And Biogeographic Study Of Trillium (Melanthiaceae), Jayne A. Lampley

Doctoral Dissertations

Trillium (Melanthiaceae, Parideae) has a disjunct distribution occurring in eastern and western North America, and eastern Asia. Past studies have examined the phylogeny and historical biogeography of Melanthiaceae and Parideae, however these studies either did not fully examine these aspects within Trillium or did not employ sufficiently broad taxonomic or character sampling to clarify relationships among taxa. The first phylogenetic analysis presented in this study provides a resolved phylogeny for Trillium s.l. and Paris s.l. by using a dataset of 70 plastid coding genes and by sampling broadly from Trillium s.s., Pseudotrillium, Trillidium, Paris s.s., Daiswa, and Kinugasa. The results …

Erecta Family Genes Regulate The Shoot Apical Meristem And Organ Formation, Daniel A. Degennaro

Doctoral Dissertations

Plants are sessile and must adjust their organ growth to their environments. A reservoir of stem cells in the shoot apical meristem (SAM) supplies cells for differentiation into organs. The SAM must balance organ production with stem cell maintenance. The ERECTA family (ERfs) encodes the leucine-rich repeat receptor-like kinases ERECTA (ER), ERECTA-LIKE 1 (ERL1), and ERL2. ERf signaling regulates organ initiation and stem cell maintenance. Results presented in this work include the following:

1) WUSCHEL (WUS) and CLAVATA3 (CLV3) make up a negative feedback loop to maintain SAM size. WUS and CLV3 expression localization is critical for …

Interseeding Native Warm-Season Grass Pastures, Jonathan D. Richwine

Doctoral Dissertations

Cool-season annual (CSA) grass and legume species, as well as warm-season forbs, can enhance established native warm-season grass (NWSG) pastures by extending the grazing season, reducing supplemental feed costs, suppressing weeds, increasing herbage production and overall forage quality, and increasing food and cover resources for pollinators and wildlife. Therefore, two NWSG experiments were conducted near Spring Hill, TN, 2018-2020, to assess three CSA seeding options (cereal rye monoculture, a cereal rye, ‘Purple Top’ turnip, ‘Trophy’ rape, ‘Frosty’ berseem clover, and ‘Dixie’ crimson clover polyculture, or non-planted control) and two warm-season N rates (0 or 67 kg N ha^-1) …

Identification And Functional Characterization Of Plant Small Secreted Proteins During Arbuscular Mycorrhizal Symbiosis, Xiaoli Hu

Doctoral Dissertations

Plant small secreted proteins (SSPs) are sequences of 50 – 250 amino acids in size which are transported out of cells to fulfill multiple functions related to plant growth and development and response to various stresses. With the development of more accurate and affordable genome sequencing technology, an increasing number of SSPs have been predicted using diverse computational tools based on machine learning. Although experimentally validated plant SSPs are still limited, some studies have reported that plant SSPs can be induced and involved in mutualistic relationships between plants and microbes. In Chapter I, known SSPs and their functions in various …

Alteration Of Potato Plastids As Platforms For Biotechnology And Synthetic Biology, Alexander C. Pfotenhauer

Doctoral Dissertations

Plastids represent a unique opportunity for plant biotechnology and synthetic biology. Their fundamental uses for photosynthesis, starch storage, and other processes can be exploited to benefit food production and other industries. In this work, we attempt to modulate these plastids in order to produce potato plants with beneficial characteristics for further use in synthetic biology. The first chapter of this dissertation involves genome-editing of the FtsZ1 gene, which is involved in plastid division. Plants were generated with large plastids and starch granules, and similar methods could be used to produce these plants without foreign DNA integration. The second chapter involves …

Characterization And Management Of Glyphosate-Resistant Junglerice, Clay M. Perkins

Doctoral Dissertations

Junglerice has become a major weed in Tennessee and across the mid-south. Glyphosate resistance and dicamba antagonism has resulted in the reported control failures and rise in prevalence. Junglerice was the most prevalent weed escape in cotton and soybean fields across Tennessee from 2018 to 2020. In all, 13% of the junglerice accessions could no longer be effectively controlled with glyphosate. Due to poor in-crop control, it has been recommended to start clean when trying to control junglerice and other grasses. Therefore, research was conducted to determine the best burndown methods utilizing dicamba, glufosinate, or paraquat. A sequential application of …

Epigenetic Mechanisms Governing Plant Growth, Development, And Responses To Nematode Parasitism, Meredith M. Bennett

Doctoral Dissertations

Epigenetic mechanisms, including histone and DNA methylation and microRNAs, play key roles in mediating transcriptional changes during plant development and stress responses. However, how these interconnected epigenetic components regulate gene expression in a spatiotemporal fashion remains partially known. Here, I generated 15 transgenic Arabidopsis GUS reporter lines for genes involved in DNA methylation and demethylation pathways. The spatiotemporal expression patterns of these genes were profiled in various plant organs during development, exogenous phytohormone response, and plant-parasitic nematode pathogenesis. The analyses revealed unique and overlapping expression patterns in roots, shoots, and reproductive organs, emphasizing the importance of a DNA methylation—demethylation equilibrium. …

Regulation Of Plasmodesmata By Specialized Metabolites Glucosinolates In Arabidopsis Thaliana, Jessica C. Fernandez

Doctoral Dissertations

Communication is an essential component to all living organisms. In

plants, the additional cell wall surrounding each cell adds a layer of complexity

not observed in animals. To overcome the literal wall separating cells, plants

have evolved specialized pores to connect adjacent cells. Plasmodesmata (PD)

allow plants to have a continuous cytoplasm between cells. Although

plasmodesmata may appear simple and lack regulation, their structural

components and their regulatory machinery is complex and not well understood.

Organelle-to-nucleus-to-plasmodesmata signaling (ONPS) have been worked as

a leading model for a possible regulatory mechanism. Many of the details of

organelle-to-nucleus retrograde signaling pathways have …

Using Multi-Omics Approaches To Study Flowering Time And Fruit Development In Perennial Fruit Species, Jiali Yu

Doctoral Dissertations

Perennial fruiting plants coordinate their reproductive activities with seasonal changes in the temperate climates, with a pattern of bud set, dormancy establishment, fulfillment of chilling, flowering, fruit set, and fruit ripening. These processes have been optimized for the production of orchard plants that reliably produce quality fruit for human consumption. The understanding of molecular controls of dormancy in fruit trees has grown rapidly in the past decade, however, the complex mechanisms remain largely unknown. This dissertation presents my findings on genetic and epigenetic changes in Prunus species from dormancy to flowering using transcriptomics and epigenomics approaches. First, I compared the …

Fungicide Sensitivity Screening Of Corynespora Cassiicola In Us Soybean And Cotton, Tyler Miles Smith

Doctoral Dissertations

Target spot, caused by the fungus Corynespora cassiicola, is a foliar disease of cotton and soybean. Target spot has become a disease of concern in soybean and cotton production systems. Data for fungicide sensitivity and understanding potential impact on yield is lacking for C. cassiicola. Fungicide resistance is also a concern in C. cassiicola with the increase in resistant pathogens in soybean. With the lack of knowledge about baseline fungicide sensitivity and the concern of fungicide resistance the objectives of this study were: (i) to evaluate fungicide products and mixes in small plot soybean and cotton trials, (ii) …