Life Sciences Commons^™

Functional Analysis Of The Mir156 Regulatory Network In Arabidopsis Siliques, Zhishuo Wang

Electronic Thesis and Dissertation Repository

Siliques are photosynthetically active seed capsules and their development is strongly influenced by embryo development. MicroRNA156 (miR156)-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) network is involved in regulating plant growth and development, but the downstream genes of this network are still not fully elucidated. Here, I show that the miR156/SPL2 pathway controls the development of floral organs, regulates pollen production, and thus affects male fertility in Arabidopsis thaliana. I present evidence that SPL2 binds to the 5’UTR of the ASYMMETRIC LEAVES 2 (AS2) gene in vivo, indicating that AS2 acts downstream of SPL2. When compared to wild-type plants, AS2 loss-of-function mutants …

Inferring Plastid Metabolic Pathways Within The Nonphotosynthetic Free-Living Green Algal Genus Polytomella, Sara Asmail

Electronic Thesis and Dissertation Repository

The advent of photosynthesis facilitated the evolution of aerobic life on Earth. However, species such as Prototheca wickerhamii and Plasmodium falciparum, among many others, have lost photosynthesis and opted for a free-living/parasitic lifestyle. Despite this loss, these species have retained the plastid for its metabolic pathways, without which they would die. Polytomella is a nonphotosynthetic free-living alga, closely related to the photosynthetic model organism Chlamydomonas reinhardtii, and has been shown to lack a plastid genome. I set out to determine Polytomella plastid metabolic pathways using bioinformatics to look for mRNA and DNA homologous sequences matching pathway enzymes in model organisms. …

Planting The Chalcone Reductase Family Tree: Identification And Characterization Of Chalcone Reductase Genes In Soybean, Caroline Julia Sepiol

Electronic Thesis and Dissertation Repository

Soybean (Glycine max [L.] Merr) is an important crop grown in Canada, generating $2.4 billion in sales. Though this number may be promising, soybean farmers lose about $50 million worth of yield annually due to root and stem rot disease caused by Phytophthora sojae. Many strategies have been developed to combat the infection; however, these methods are prohibitively expensive. A ‘cost effective’ approach to this problem is to select a trait naturally found in soybean that can increase resistance. One such trait is the increased production of root glyceollins. One of the key enzymes exclusively involved in glyceollin …

Genetic Analysis Of A Non-Germinating Mutant Of Arabidopsis Thaliana, Md Jakir Hossan

Electronic Thesis and Dissertation Repository

Seed germination is partially controlled by plant hormone gibberellins (GAs). Chemical mutagenesis yielded an Arabidopsis thaliana mutant gm11, which has an absolute gibberellin requirement for seed germination. This mutant exhibited phenotypes of GA-rescuable dwarfs, including dark-green leaves, and reduced fertility. However, with repeated GA treatment, gm11 develops into fertile plants with a nearly wild type phenotype. Bulked-segregant analysis mapped gm11 to the bottom arm of chromosome 1, and subsequent next-generation mapping revealed that the mutation is a G → A transition in At1g79460 (GA2), creating a premature stop codon. This gene encodes an ent-kaurene synthase (KS) which catalyzes …

Ginsenosides, Glycosidases And The Ginseng-Pythium Interaction, Dimitre A. Ivanov

Electronic Thesis and Dissertation Repository

Ginsenosides, the triterpenoid saponins produced by American ginseng (Panax quinquefolius L.), have been extensively studied for their medicinal value, however, their function in the rhizosphere remains largely unknown. Like other saponins, ginsenosides possess mild fungitoxic activity toward some common ginseng pathogens. However, numerous oomycete root pathogens of ginseng, most notably Pythium irregulare Buisman, are able to partially deglycosylate the 20 (S)-protopanaxadiol ginsenosides Rb1, Rd and gypenoside XVII via extracellular glycosidases (ginsenosidases), leading to the formation of a common product, ginsenoside F2. In this thesis the potential role(s) of these extracellular ginsenosidases and the ginsenoside products they produce (ie. ginsenoside …

Identification Of Putative Plant Defense Genes Using A Novel Hydroponic Co-Cultivation Technique For Studying Plant-Pathogen Interaction, Naeem Nathoo

Electronic Thesis and Dissertation Repository

Previous work on identifying the molecular mechanisms mediating plant-pathogen interactions and reciprocal host responses have little emphasis on developing models that closely resemble host-microbe interaction in planta. This work establishes an amalgamated model of interaction wherein successful pathogens elicit and overcome host defenses activated by microbial signatures and virulence factors. Using a hydroponic co-cultivation model, we assessed the responses of Arabidopsis thaliana Col-0 to Agrobacterium tumefaciens C58 to ameliorate limitations of previous approaches. Comparisons of differential gene expression between directly and indirectly affected host sites by microarray analysis revealed both reactive and pro-active defense responses, respectively. Selected homozygous single-gene …

Effects Of Growth Temperatures And Elevated Co2 On Respiration Rates In Norway Spruce, Yulia Kroner

Electronic Thesis and Dissertation Repository

Projected increase in growth temperatures and CO₂ may affect carbon balance in Norway spruce (Picea abies), a dominant coniferous species of the boreal forest ecosystem. To examine this, I exposed three-year-old Norway spruce seedlings to six treatments: ambient (400 ppm) and elevated (750 ppm) CO₂ concentrations combined with three growth temperatures: ambient, ambient +4 ^oC, and ambient +8 ^oC. I found that while net growth was generally not affected by growth CO₂ or temperature, leaf nitrogen concentrations were reduced, mortality rates were higher, and needles were shorter and thinner in +8 ^oC …

Soybean Isoflavonoid Biosynthesis: Constituents And Circumstance At The Transcriptomic And Molecular Levels, Mehran Dastmalchi

Electronic Thesis and Dissertation Repository

Isoflavonoids are specialized metabolites, almost exclusive to the legume family of plants. They are actors in symbiosis with nitrogen-fixing bacteria and in plant stress response. Isoflavonoids are noted for their human health benefits. Isoflavonoid content in legumes has proven to be a complex trait. The goal of the present research is to determine the mechanisms underlying isoflavonoid biosynthesis in soybean.

The first approach was to unravel the genetic factors of isoflavonoid biosynthesis. A branch-point enzyme of the phenylpropanoid pathway, chalcone isomerase (CHI), catalyzes the reaction producing flavanones, the nucleus for many downstream metabolites such as isoflavonoids. I identified twelve soybean …