Life Sciences Commons^™

Functional Characterization Of The Hua2 Gene Family In Arabidopsis Thaliana, Preetam Janakirama

Electronic Thesis and Dissertation Repository

HUA2 encodes a key developmental regulatory protein implicated in the coordination of induction and the maintenance of floral state in Arabidopsis. To gain further insight into the function of HUA2, I have conducted a series of studies aimed at elucidating the molecular function(s) of its individual domains. I show that the PWWP, RPR and CT-proline rich domains within HUA2 are required for the proper regulation of the flowering time phenotype. I also establish that HUA2 interacts with characterized splicing factors (FCA, AtPRP40, RBP45 and UBP1) through its CT-proline rich domain. In addition, I examine the overlap in function between HUA2 …

Sunergos1, A Lotus Japonicus Gene Required For Proper Accommodation Of Rhizobial Infection, Hwi Joong Yoon

Electronic Thesis and Dissertation Repository

Here, I characterize a symbiotic mutant of Lotus japonicus, called sunergos1 (suner1), which originated from a har1-1 suppressor screen. I have shown that suner1 supports epidermal infection by rhizobia and initiates nodule primordia organogenesis as in wild-type. However, the infection process is temporarily stalled, such that infection threads fail to ramify within the root cortex and timely release of bacteria inside the nodule primordia cells does not occur. This symbiotic defect is ephemeral and with additional time, functional nodules are formed. Using a combined approach involving map-based cloning and next-generation sequencing, I have shown that the suner1 …

Har1 And Ljamp1 Dependent Regulation Of Root Architecture In Lotus Japonicus, Chong Sung Kim

Electronic Thesis and Dissertation Repository

Here, I characterize a root-branching hypermorph of Lotus japonicus, called cluster root-like1 (crl1), which originated from a har1-1 suppressor screen. I have shown that the crl1 root phenotype is determined by two independently segregating recessive mutations, har1-1 and Ljamp1-1, with corresponding HAR1 and LjAMP1 encoding an LRR‑receptor-like kinase and a predicted homologue of the Arabidopsis ALTERED MERISTEM PROGRAM 1 protein, respectively. Unlike har1-1, the Ljamp1 mutation does not affect the symbiotic properties of L. japonicus Gifu but exerts a pleiotropic effect on shoot development. Root architecture, however, is regulated by a synergistic action of HAR1 …

Involvement Of Hexokinase1 In Plant Growth Promotion As Mediated By Burkholderia Phytofimans, Jae Min Park

Electronic Thesis and Dissertation Repository

Burkholderia phytofirmans strain PsJN consistently enhanced the growth of potato plants in vitro. The role of hexokinase1 in glucose phosphorylation was investigated in plants with PsJN. Increased hexokinase1 activity only in roots of PsJN-treated plants cultivar Kennebec suggests that hexokinase1 is associated with plant root and stem growth.

Plant growth with PsJN was determined when plants were grown with different sugars at various concentrations. PsJN-treated plants expressed diverse forms of growth promotion. When growth promotion did occur, hexokinase1 activity also increased. Growth promotion and hexokinase1 activity appear to be correlated to the enzyme to recognize the substrate for catalytic activity. …

Cadmium Accumulation And Distribution In Lettuce And Barley, Fardausi Akhter

Electronic Thesis and Dissertation Repository

Cadmium (Cd) is a non-essential trace element and its environmental concentrations are increasing due to human activities. Edible plants can accumulate high concentrations of Cd, which could be toxic to humans. Understanding how and where Cd is stored in plants is important for ensuring lower concentration of Cd in the food. In this thesis, the accumulation and distribution of Cd in three agricultural plants, namely lettuce (Lactuca sativa L.), barley (Hordeum vulgare L.) and radish (Raphanus sativus L.), were investigated with a focus on the potential mechanisms involved in the localization of Cd in the root. The …

Protein Body Formation In Stable Transgenic Plants Of Nicotiana Tabacum Expressing Elastin-Like Polypeptide And Hydrophobin Fusion Proteins, Sonia P. Gutierrez

Electronic Thesis and Dissertation Repository

Plants are recognized as an efficient and inexpensive system to produce valuable recombinant proteins. However, the use of plants still faces two main limitations: the low accumulation levels of some recombinant proteins and the lack of efficient protein purification methods. Two fusion partners, elastin-like polypeptides (ELP) and hydrophobin I (HFBI) were found to increase the accumulation of recombinant proteins and induce the formation of protein bodies (PBs) when targeted to the ER in transient expression assays. In this study I examined the effect of these tags in stable transgenic plants of two Nicotiana tabacum cultivars when fused to green fluorescent …

Hairy Roots As A Model To Investigate The Role Of Suberin In The Phytophthora Sojae-Soybean Pathosystem, Pooja Sharma

Electronic Thesis and Dissertation Repository

Part of the resistance mechanism of soybean (Glycine max [L.] Merr.) to Phytopthora sojae Kauf. & Gerd. involves pre-formed root suberin. In order to investigate the role of suberin in this host-pathogen interaction, I characterized hairy roots, formed as a result of Agrobacterium rhizogenes (Riker et al.) Conn infection, as a model to be used as a reliable soybean transformation system. I established hairy root cultures and demonstrated that they were a result of A. rhizogenes infection. The anatomy and suberin deposition in soybean hairy roots was examined, and found to be very similar to that of wild-type roots. …

Colonization Of Zea Mays By The Nitrogen Fixing Bacterium Gluconacetobacter Diazotrophicus, Nikita Eskin

Electronic Thesis and Dissertation Repository

To achieve high yields, corn fields are supplemented with nitrogen fertilizers. Nitrogen fertilizers account for a significant portion of production costs, and are harmful to the environment. Gluconacetobacter diazotrophicus, an endophytic nitrogen-fixing bacterium supplies its natural host sugarcane with a significant amount of nitrogen. This study investigated the colonization of G. diazotrophicus in seven different corn genotypes consisting of sweet and grain corn via three different methods of inoculation: soil drench, root dip, and aseptic inoculation. Sucrose content of the corn genotypes and nitrogenase activity were also analysed. Colonization was confirmed by PCR analysis. G. diazotrophicus colonization was detected using …

Identification And Characterization Of The Arabidopsis Homolog Of The Yeast Trex-2 Complex, Gang Tian

Electronic Thesis and Dissertation Repository

Nuclear pore complexes (NPCs) are vital to nuclear-cytoplasmic communication in eukaryotes. The yeast Thp1-Sac3-Cdc31-Sus1 complex, also known as the TREX-2 complex, is anchored to the NPC via the nucleoporin Nup1, and is essential for mRNA export. In this study, the Arabidopsis homolog of the yeast TREX-2 complex was discovered. Physical and functional evidence support the identification of the Arabidopsis orthologs of the yeast Thp1 and Nup1. Of three Sac3 Arabidopsis homologs, two are putative TREX-2 components. Surprisingly, none are required for mRNA export as is the yeast Sac3. Physical association with TREX-2 was observed for the two Cdc31 homologs, but …

The Influence Of Ambient Environment On The Growth And Fitness Of Glyphosate-Resistant And -Susceptible Giant Ragweed (Ambrosia Trifida L.) Biotypes, Julia A. Thompson

Electronic Thesis and Dissertation Repository

Glyphosate-resistant giant ragweed can be found in agricultural fields throughout the mid-western United States and southwestern Ontario. Environmental factors can influence growth and herbicide efficacy in C₃ plant species. I measured the aboveground injury to resistant and susceptible seedlings for 28 d following glyphosate treatment to test the hypothesis that young leaf stages would be more susceptible to glyphosate under warm, dry, low-CO₂ conditions. Glyphosate-resistance was not affected by environmental factors, leaf stage, or glyphosate dose, but plants grown at the highest temperature after spray had the least glyphosate injury. Resistant alleles may be associated with fitness penalties …

Brassinosteroid-Mediated Stress Tolerance In Arabidopsis Thaliana, Tawhidur Rahman

Electronic Thesis and Dissertation Repository

Brassinosteroids (BRs) are a group of steroidal plant hormones that are essential for proper plant development and also promote stress tolerance. Without BRs, plants are dwarfs and infertile. To understand the molecular mechanisms underlying BR-mediated stress tolerance, global gene expression analysis of untreated and 24-epibrassinolide (EBR)-treated Arabidopsis thaliana seedlings under non-stress and heat stress (HS) conditions was carried out. Microarray data analysis indicated that stress-related genes were predominant within the EBR up-regulated gene data set. Furthermore, several of these genes were abscisic acid (ABA) and jasmonic acid (JA) related. Measurements of endogenous hormones showed significant increases in the levels ABA …

Trace Metal Limitation And Its Role In Oxidative Stress Of Coral Algal Symbionts; Implications For Thermally Induced Coral Bleaching Events., Katrina Lynn Iglic

Electronic Thesis and Dissertation Repository

Coral bleaching, the process in which corals expel their photosynthetic symbionts (Genus Symbiodinium), is caused by high temperature and irradiance stress. The synergistic effect of each stressor is the generation of damaging reactive oxygen and nitrogen species (ROS and RNS), which are normally mitigated physiologically by antioxidant enzyme activity. Antioxidant enzymes require iron, copper, manganese and zinc in their structure and the limited nature of these trace metals in reef environments may enhance ROS production under elevated temperature and irradiance. The hypothesis tested within this thesis was that a limited availability of the trace metals Fe, Mn, Cu and …