Plant Biology Commons^™

Analysis Of Alternative Oxidase In Non-Angiosperm Plants, Anissa M. Francis

Theses and Dissertations (Comprehensive)

Alternative oxidase (AOX) is a mitochondrial terminal oxidase that provides an alternative pathway for electron transport, allowing plants to maintain respiratory flexibility under environmental stress conditions. While AOX has been extensively studied in angiosperms (flowering plants), little is known about its distribution and conservation in non-angiosperms. Based on gaps identified in the literature, this thesis investigated the distribution of AOX across non-angiosperm plant lineages. Although AOX is present in many green algae and is therefore considered to be an ancient protein that originated before the existence of non-angiosperm plants, it remains unclear whether the protein is uniformly distributed across these …

Characterizing The Targeting Of Toc159 Receptors To The Chloroplast Outer Envelope Membrane And Their Role In The Assembly Of Distinct Toc Complexes, Michael Fish

Theses and Dissertations (Comprehensive)

Global agriculture and food security face challenges from climate change, population growth, and other human-driven pressures. Enhancing our understanding of plant biology, particularly chloroplast function, is critical for improving crop yield and stress resilience. As the sites of photosynthesis and key regulators of plant responses to environmental cues, chloroplasts depend on the precise import of thousands of nuclear-encoded proteins to maintain their biogenesis and function. While much is known about the core translocon components in the chloroplast outer envelope membrane that form the TOC complex, the mechanisms underlying their targeting, assembly, and regulation remain incompletely understood.

Plastids, including chloroplasts, evolved …

Npr1 As A Temperature-Sensitive Regulator Of Pipecolic Acid-Mediated Plant Systemic Immunity, Spencer Tout

Theses and Dissertations (Comprehensive)

Healthy plant development requires balancing both abiotic (e.g. climate) and biotic (e.g. pathogen) challenges, which intercept important signaling pathways in plants. For example, climate change-associated elevated temperature can negatively modulate various aspects of plant immunity, including the production of central immune signals salicylic acid (SA) and N-hydroxypipecolic acid (NHP). Since SA and NHP signaling both require the master immune co-activator protein NON-EXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1), it is important to investigate NPR1 as a potentially temperature-regulated molecular hub. Although the NPR1 gene is not transcriptionally downregulated at elevated temperatures (28° C vs. 23° C), little is known about …

The Plant Disease Triangle Facing Climate Change: A Molecular Perspective, Charles Roussin-Léveillée, Christina A. M. Rossi, Christian Castroverde, Peter Moffett

Biology Faculty Publications

No abstract provided.

Structural Diversity And Stress Regulation Of The Plant Immunity-Associated Calmodulin-Binding Protein 60 (Cbp60) Family Of Transcription Factors In Solanum Lycopersicum (Tomato), Vanessa Shivnauth, Sonya Pretheepkumar, Eric J. R. Marchetta, Christina A. M. Rossi, Keaun Amani, Christian Castroverde

Biology Faculty Publications

Cellular signaling generates calcium (Ca2+) ions, which are ubiquitous secondary messengers decoded by calcium-dependent protein kinases, calcineurins, calreticulin, calmodulins (CAMs), and CAM-binding proteins. Previous studies in the model plant Arabidopsis thaliana have shown the critical roles of the CAM-BINDING PROTEIN 60 (CBP60) protein family in plant growth, stress responses, and immunity. Certain CBP60 factors can regulate plant immune responses, like pattern-triggered immunity, effector-triggered immunity, and synthesis of major plant immune-activating metabolites salicylic acid (SA) and N-hydroxypipecolic acid (NHP). Although homologous CBP60 sequences have been identified in the plant kingdom, their function and regulation in most species remain unclear. In …

Molecular Regulation Of The Salicylic Acid Hormone Pathway In Plants Under Changing Environmental Conditions, Christina A. M. Rossi, Eric J. R. Marchetta, Jong Hum Kim, Christian Castroverde

Biology Faculty Publications

Salicylic acid (SA) is a central plant hormone mediating immunity, growth, and development. Recently, studies have highlighted the sensitivity of the SA pathway to changing climatic factors and the plant microbiome. Here we summarize organizing principles and themes in the regulation of SA biosynthesis, signaling, and metabolism by changing abiotic/biotic environments, focusing on molecular nodes governing SA pathway vulnerability or resilience. We especially highlight advances in the thermosensitive mechanisms underpinning SA-mediated immunity, including differential regulation of key transcription factors (e.g., CAMTAs, CBP60g, SARD1, bHLH059), selective protein–protein interactions of the SA receptor NPR1, and dynamic phase separation of the recently identified …

Natural Variation In Temperature-Modulated Immunity To Pseudomonas Syringae Pv. Tomato (Pst Dc3000) In Arabidopsis Thaliana Plants, Christina A. M. Rossi

Theses and Dissertations (Comprehensive)

Studies conducted on the model plant-pathogen system Arabidopsis thaliana-Pseudomonas syringae pv. tomato (Pst) showed that elevated temperature suppresses the pathogen-induced production of salicylic acid (SA), which is a key plant defence hormone. This increased host vulnerability at higher temperatures is due to downregulated expression of CALMODULIN BINDING PROTEIN 60-LIKE G (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1), which encode master regulators of SA production. Collectively, these previous studies only focused on one natural accession of Arabidopsis called Columbia-0 (Col-0). However, the intraspecific variation in Arabidopsis immunity phenotypes under elevated temperature remains unknown. To fill this critical knowledge gap, my …

Winter Dynamics Of Storm Water Management Ponds And Winter Tolerance In Three Aquatic Plant Species, Patrick Strzalkowski

Theses and Dissertations (Comprehensive)

The vast majority of the research into the performance of stormwater management ponds (SWMPs) has been performed in warm regions or during the warmer seasons in temperate regions. It is presumed that SWMPs are inactive in the winter as any potential stormwater is trapped in snow and ice. The main goal of this thesis was to test this presumption and to study the dynamics and performance of three SWMPs during the winter. Remote water level loggers were installed into the three SWMPs and daily grab samples from the influents and effluents were taken and analyzed for total phosphorus (TP), chloride, …

Increasing The Resilience Of Plant Immunity To A Warming Climate, Jong Hum Kim, Christian Castroverde, Shuai Huang, Chao Li, Richard Hilleary, Adam Seroka, Reza Sohrabi, Diana Medina-Yerena, Bethany Huot, Jie Wang, Sharon Marr, Mary Wildermuth, Tao Chen, John Macmicking, Sheng Yang He

Biology Faculty Publications

Extreme weather conditions associated with climate change affect many aspects of plant and animal life, including the response to infectious diseases. Production of salicylic acid (SA), a central plant defence hormone, is particularly vulnerable to suppression by short periods of hot weather above the normal plant growth temperature range via an unknown mechanism. Here we show that suppression of SA production in Arabidopsis thaliana at 28 °C is independent of PHYTOCHROME B (phyB) and EARLY FLOWERING 3 (ELF3), which regulate thermo-responsive plant growth and development. Instead, we found that formation of GUANYLATE BINDING PROTEIN-LIKE 3 (GBPL3) defence-activated biomolecular condensates (GDACs) …

Salicylic Acid And N-Hydroxypipecolic Acid At The Fulcrum Of The Plant Immunity-Growth Equilibrium, Alyssa Shields, Vanessa Shivnauth, Christian Danve M. Castroverde

Biology Faculty Publications

Salicylic acid (SA) and N-hydroxypipecolic acid (NHP) are two central plant immune signals involved in both resistance at local sites of pathogen infection (basal resistance) and at distal uninfected sites after primary infection (systemic acquired resistance). Major discoveries and advances have led to deeper understanding of their biosynthesis and signaling during plant defense responses. In addition to their well-defined roles in immunity, recent research is emerging on their direct mechanistic impacts on plant growth and development. In this review, we will first provide an overview of how SA and NHP regulate local and systemic immune responses in plants. We …

Diversity And Evolution Of Inflorescences In Cuscuta, Morgan Glofcheskie

Theses and Dissertations (Comprehensive)

Cuscuta (dodder) includes ca. 200 species of plant obligate stem parasites with both ecological and economical significance. Inflorescences have been historically used in Cuscuta for species descriptions and identification keys, but no comprehensive study exists to date. The main objective of this study was to survey the diversity of inflorescences, and to understand their evolution and possible form-function relationships. The inflorescence architecture of 132 Cuscuta taxa was analyzed using herbarium specimens, and eight species were grown to study their inflorescence development. Inflorescence traits were mapped into a genus phylogeny obtained from a combined analysis of nuclear ITS and plastid trnL-F …

Changes In Plant Community Composition, Structure, And Function In Response To Permafrost Thaw, Katherine Standen

Theses and Dissertations (Comprehensive)

Air temperature is increasing at three or more times the global average in high latitudes, causing widespread permafrost thaw across the boreal biome. Since the boreal biome stores 30-40% of global terrestrial carbon (C), of which about 30-45% is found in permafrost soils, this temperature increase could cause a large efflux of C to the atmosphere. Climate warming and permafrost thaw are also expected to alter plant community composition and productivity and, given the link between plant functional traits and ecosystem C fluxes, may alter overall ecosystem function. Across the boreal biome of western Canada, we know surprisingly little about …

Salicylic Acid: A Key Regulator Of Redox Signalling 1 And Plant Immunity, Mohd Saleem, Qazi Fariddudin, Christian Castroverde

Biology Faculty Publications

In plants, the reactive oxygen species (ROS) formed during normal conditions are essential in regulating several processes, like stomatal physiology, pathogen immunity and developmental signaling. However, biotic and abiotic stresses can cause ROS over-accumulation leading to oxidative stress. Therefore, a suitable equilibrium is vital for redox homeostasis in plants, and there have been major advances in this research arena. Salicylic acid (SA) is known as a chief regulator of ROS; however, the underlying mechanisms remain largely unexplored. SA plays an important role in establishing the hypersensitive response (HR) and systemic acquired resistance (SAR). This is underpinned by a robust and …

Temperature Regulation Of Plant Hormone Signaling During Stress And Development, Christian Castroverde, Damaris Dina

Biology Faculty Publications

Global climate change has broad-ranging impacts on the natural environment and human civilization. Increasing average temperatures along with more frequent heat waves collectively have negative effects on cultivated crops in agricultural sectors and wild species in natural ecosystems. These aberrantly hot temperatures, together with cold stress, represent major abiotic stresses to plants. Molecular and physiological responses to high and low temperatures are intricately linked to the regulation of important plant hormones. In this review, we shall highlight our current understanding of how changing temperatures regulate plant hormone pathways during immunity, stress responses and development. This article will present an overview …

Wildlife Forage Recovery Following Boreal Wildfire, Alexis Jorgensen, Jennifer Baltzer

Theses and Dissertations (Comprehensive)

Climate change is altering the boreal wildfire regime through increases in the extent and severity of burning and reductions in fire return intervals. These changes can alter the regeneration trajectory of canopy species and ground vegetation, with implications for wildlife habitat. There is some uncertainty about the timelines of when different animal species will use burned areas as their preferred forage taxa recover following fire, and how such recovery is mediated by environmental factors. Here, we aim to address these knowledge gaps through the following questions: 1) What are the main forage types consumed by boreal wildlife and how much …

Mechanistic Insights Into Strigolactone Biosynthesis, Signaling And Regulation During Plant Growth And Development, Kaiser Iqbal Wani, Andleeb Zehra, Sadaf Choudhary, M Naeem, M. Masroor A. Khan, Christian Danve Castroverde, Tariq Aftab

Biology Faculty Publications

Strigolactones (SLs) constitute a group of carotenoid-derived phytohormones with butenolide moieties. These hormones are involved in various functions, including regulation of secondary growth, shoot branching and hypocotyl elongation, and stimulation of seed germination. SLs also control hyphal branching of arbuscular mycorrhizal (AM) fungi, and mediate responses to both abiotic and biotic cues. Most of these functions stem from the interplay of SLs with other hormones, enabling plants to appropriately respond to changing environmental conditions. This dynamic interplay provides opportunities for phytohormones to modulate and augment one another. In this article, we review our current mechanistic understanding of SL biosynthesis, receptors …

Diversity, Function And Regulation Of Cell Surface And Intracellular Immune Receptors In Solanaceae, Jong Hum Kim, Christian Castroverde

Biology Faculty Publications

The first layer of the plant immune system comprises plasma membrane-localized receptor proteins and intracellular receptors of the nucleotide-binding leucine-rich repeat protein superfamily. Together, these immune receptors act as a network of surveillance machines in recognizing extracellular and intracellular pathogen invasion-derived molecules, ranging from conserved structural epitopes to virulence-promoting effectors. Successful pathogen recognition leads to physiological and molecular changes in the host plants, which are critical for counteracting and defending against biotic attack. A breadth of significant insights and conceptual advances have been derived from decades of research in various model plant species regarding the structural complexity, functional diversity and …

A Stimulatory Role For Cytokinin In The Arbuscular Mycorrhizal Symbiosis Of Pea, Dane M. Goh, Marco Cosme, Anna B. Kislala, Samantha Mulholland, Zakaria M.F. Said, Lukáš Spíchal, R.J. Neil Emery, Stéphane Declerck, Frédérique C. Guinel

Biology Faculty Publications

The arbuscular mycorrhizal (AM) symbiosis between terrestrial plants and AM fungi is regulated by plant hormones. For most of these, a role has been clearly assigned in this mutualistic interaction; however, there are still contradictory reports for cytokinin (CK). Here, pea plants, the wild type (WT) cv. Sparkle and its mutant E151 (Pssym15), were inoculated with the AM fungus Rhizophagus irregularis. E151 has previously been characterized as possessing high CK levels in non-mycorrhizal (myc^-) roots and exhibiting high number of fungal structures in mycorrhizal (myc⁺) roots. Myc^- and myc⁺ plants were …

Context Is Everything: An Investigation Of Spanish River Carbonatite And Its Effects On Soil-Plant-Microorganism Systems, James Mc Jones

Theses and Dissertations (Comprehensive)

With growing concerns about agricultural sustainability and food security, the use of rock fertilizers and agrominerals is receiving renewed interest. A wide variety of geological resources have been proposed as crop nutrient sources, with silicate rocks the predominant focus. Carbonatite rocks are known to weather more readily than silicate rocks; yet, they have received relatively little attention as it is thought their high Ca and Mg contents hinder effective nutrient release. However, there is strong evidence that the nutrients within carbonatite rocks are easily accessible to plants, and that these rocks have noticable effects on crop plant growth. Here I …

Going Back To The Soil: An Integrated Approach To Farming., Renée V. Christie

Theses and Dissertations (Comprehensive)

Agricultural productivity is often constrained by nutrient availability; as such, copious amounts of synthetic fertilizers are applied to maintain productivity. However, the intensive use of synthetic fertilizers has reduced the capacity of the soil to carry out crucial roles such as nutrient cycling because of shifts in the microbial community composition and structure. In addition, much of the applied synthetic fertilizers become lost to the environment through run-off, which contributes to soil degradation. With the increasing demand on agricultural systems to provide food and fibre and the adverse impacts of agricultural production on the soil resource, amendments that support soil …

Diversity And Evolution Of Seeds In Cuscuta (Dodders, Convolvulaceae): Morphology And Structure, Magdalena Olszewski

Theses and Dissertations (Comprehensive)

Cuscuta is a genus of nearly 200 obligate stem parasites with a nearly cosmopolitan distribution and considerable agricultural and ecological significance. Dodder seeds are considered “unspecialized”, with no morphological adaptations towards particular dispersal vectors; however, the seed coat anatomy has recently suggested an adaptation to endozoochory. This is the first attempt to provide a genus-wide overview of the diversity in morphology and anatomy of Cuscuta seeds, together with an assessment of the water gap and exploration of various form-function relationships. I surveyed 104 species belonging to all four Cuscuta subgenera. Seeds of the species of the first infrageneric dodder …

Competition Or Facilitation: Examination Of Interactions Between Endangered Sida Hermaphrodita And Invasive Phragmites Australis, Samantha N. Mulholland

Theses and Dissertations (Comprehensive)

Virginia Mallow (Sida hermaphrodita) is a perennial herb of the Malvaceae family that is native to riparian habitats in northeastern North America. Throughout most of its geographical distribution however, it is considered threatened and only two populations are known from Canada. The biology and ecology of S. hermaphrodita are still poorly understood and although few studies have been performed to determine the factors that contribute to the species rarity, it is considered threatened potentially due to the loss of habitat caused by exotic European Common reed (Phragmites australis subsp. australis) invasion. Allelopathic and phytotoxic conditioning of …

Yardwork: A Biography Of An Urban Place By Daniel Coleman, Vivian M. Hansen

The Goose

Review of Daniel Coleman's Yardwork: A Biography of an Urban Place.

Influence Of Topography And Moisture And Nutrient Availability On Green Alder Function On The Low Arctic Tundra, Nt, Katherine Louise Black Ms., Jennifer Lynn Baltzer Dr.

Theses and Dissertations (Comprehensive)

The Arctic has warmed by at least 3^°C over the past 50 years and this rapid warming is expected to continue. Climate warming is driving the proliferation of shrubs across the tundra biome with implications for energy balance, climate, hydrology, nutrient cycling, and biodiversity. Changes in tundra plant water use attributable to shrub expansion are predicted to increase evapotranspirative water loss which may amplify local warming and reduce run-off. However, little is known about the extent to which shrubs will enhance evapotranspirative water loss in these systems. Direct measures of shrub water use are needed to accurately predict …

Spanish River Carbonatite: Its Benefits And Potential Use As A Soil Supplement In Agriculture, James J

Theses and Dissertations (Comprehensive)

A critical problem facing agriculture today is being able to consistently and sustainably provide plants with adequate nutrients for growth. With this problem being exacerbated by the ever-increasing human population, new perspectives and techniques are required to ensure global food security. In order to fully realize potential solutions, however, plant growth and nutrition cannot be exclusively focused upon. The soil-microorganism-plant system is comprised of many interconnected and interdependent processes that together support plant growth: it is upon these processes that the focus must be placed. In this work, the agromineral Spanish River Carbonatite (SRC) is characterized using the framework of …

Morphology, Structure, Function And Evolution Of Infrastaminal Scales In Cuscuta (Convolvulaceae), Stephanie Riviere

Theses and Dissertations (Comprehensive)

Cuscuta (dodder, Convolvulaceae) is a genus of about 200 species of obligate stem parasites of cosmopolitan distribution. Infrastaminal scales (IFS) are staminode-like formations that surround the ovary in the flowers of dodders. Their morphological diversity has historically provided some of the most useful taxonomic diagnostic characters at the species-level, however, their function had not been determined. I performed a comparative study of the IFS in 147 taxa using light, scanning and transmission electron microscopy, and results were analyzed in relation to a Cuscuta phylogeny obtained from a combined analysis of rbcL and 26S rDNA gene sequences. To test the hypothesis …

The Role Of The Acidic Domain Of The Toc159 Protein Import Receptor Family In Toc Complex Assembly In Arabidopsis Thaliana, Yi Chen

Theses and Dissertations (Comprehensive)

Most chloroplast proteins are encoded in the nucleus and translated in the cytosol with an N-terminal cleavable transit peptide, which can be recognized by the translocon at the outer envelope membrane of chloroplasts (Toc complex). The core Toc complex is composed of two GTPases, Toc159 and Toc34, and the Toc75 channel. atToc159, atToc132 and atToc120 are homologues of the Toc159 family in Arabidopsis, and have been shown to assemble into structurally and functionally distinct Toc complexes. Targeting of atToc159 to the chloroplast outer membrane is mediated by its GTPase (G-) domain. However, the role of the acidic (A-) domain in …

Molecular Studies Of 5-Azacytidine-Induced Early-Flowering Lines Of Flax, Megan A. House

Theses and Dissertations (Comprehensive)

Several early-flowering flax (Linum usitatissimum L.) lines were derived from treatment of germinating seeds with 5-azacytidine in 1990. These lines are also shorter, have fewer leaves, and their DNA is hypomethylated, relative to their corresponding controls. The work presented in this thesis used early-flowering and control lines of the Royal (R) flax genotype, and the Large (L) flax genotroph. Firstly, levels of cytosine methylation were measured over a 24-hour period in the early-flowering line RE2 and its control (RC), using an HPLC method. Secondly, to determine the response of the flax lines to short-day conditions, control and early-flowering …

Insights Into The World Of Pea Nodulation Using The Low Nodulator R50, Scott Clemow

Theses and Dissertations (Comprehensive)

Cytokinin oxidase (CKX) is the enzyme responsible for the degradation of cytokinin, a class of adenine-based plant hormones that stimulate cell division, among other physiological processes. The pea mutant R50 is characterized by having a pale leaf phenotype, dwarf stature, few lateral roots, low nodule formation, and elevated levels of endogenous cytokinins in its shoots, roots and nodules. When compared to that of the wild-type Sparkle, total CKX activity is low but the transcript levels of PsCKX1 are significantly higher. In this study, I investigated the expression of PsCKX1 throughout the development of a nodule and the localization of PsCKX1 …

Evolution And Systematic Significance Of Reproductive Structures In The Genus Cuscuta (Dodders, Convolvulaceae): Pollen And Gynoecium, Mark Welsh

Theses and Dissertations (Comprehensive)

The genus Cuscuta (dodders, Convolvulaceae) is one of the most significant lineages of parasitic plants from economic, conservation, and anthropogenic perspectives. Members of the genus are twining stem parasites with no roots, lacking almost completely chlorophyll or its function, and gather required nutrition from their host via specialized haustorial connections. While there are almost 200 described species, problems with species identification exist because many diagnostic characters are restricted to their tiny flowers. Probably contributing to this identification difficulty is the fact that the group has not received taxonomic attention for over 75 years; even knowledge of its basic reproductive biology …