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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

Genetics

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Tno1 & Vps45: Snare-Associated Proteins Required For Plant Growth, Rahul Roy Jan 2016

Tno1 & Vps45: Snare-Associated Proteins Required For Plant Growth, Rahul Roy

Graduate Theses and Dissertations

Cellular trafficking of cargo vesicles at the trans-Golgi network (TGN) is required for multiple processes such as cell expansion, stress responses and hormonal transport in plants. Activity of membrane proteins known as SNAREs drives membrane fusion events. Associated proteins such as tethering factors and Sec1/Munc18 proteins aid the fidelity and efficiency of these fusion events by interacting with SNAREs. The TGN-localized SYP41/SYP61/VTI12 SNARE complex is required for vacuolar and secretory cargo trafficking.

TNO1, a putative tethering factor, associates with SYP41 and is required for TGN membrane fusion dynamics and proper SYP61 localization. My dissertation research discovered a ...


Optimal Population Value Selection: A Population-Based Selection Strategy For Genomic Selection, Matthew Daniel Goiffon Jan 2016

Optimal Population Value Selection: A Population-Based Selection Strategy For Genomic Selection, Matthew Daniel Goiffon

Graduate Theses and Dissertations

In order to feed the world’s growing population, an interdisciplinary effort is needed. In this thesis, operations research tools of mathematical modeling, optimization, and simulation are used to improve an existing plant breeding method, genomic selection. To do this, a new method, called optimal population value (OPV) selection, is proposed. In this paper, OPV selection is first defined as an optimization problem that selects a breeding population using a population metric, instead of individual metrics. Then, OPV selection is thoroughly tested in a simulation study against the existing methods of genomic selection, weighted genomic selection, and optimal haploid value ...


Analysis Of Cytokinin-Induced Maize Leaf Developmental Changes And Interacting Genetic Modifiers, James Francis Cahill Jan 2015

Analysis Of Cytokinin-Induced Maize Leaf Developmental Changes And Interacting Genetic Modifiers, James Francis Cahill

Graduate Theses and Dissertations

Four distinct segments define the maize leaf along the proximal-distal axis: the proximal sheath and the distal blade, which are separated by the ligule and auricle. The process of maize leaf morphogenesis, patterning and development requires the coordination of a number of proteins and hormones. The semi-dominant gain-of-function mutant Hairy sheath frayed1 (Hsf1) disrupts a number of leaf growth parameters: (i) leaves are shorter and more narrow, (ii) an increased density of macrohairs are apparent on the abaxial sheath and adaxial blade and (iii) the normal proximal-distal leaf pattern is disrupted, resulting in outgrowths, or prongs, of ectopic sheath, auricle ...


The Co2 Concentrating Mechanism And Nitrogen Starvation Effects Under Photoautotrophic Culture Conditions Of Chlamydomonas Reinhardtii Studied By High Throughput Dna Sequencing Technology, Wei Fang Jan 2015

The Co2 Concentrating Mechanism And Nitrogen Starvation Effects Under Photoautotrophic Culture Conditions Of Chlamydomonas Reinhardtii Studied By High Throughput Dna Sequencing Technology, Wei Fang

Graduate Theses and Dissertations

The green algae species Chlamydomonas reinhardtii can acclimate to varied environmental CO2 concentration through an inducible CO2 concentration mechanism (CCM). The chloroplast stroma protein gene LCIB mutant strains exhibits an "air dier" phenotype, which demonstrated the acclimations are different in these conditions. This project first used RNA-Seq to query the Chlamydomonas reinhardtii transcriptome for regulation by CO2 and by the transcription regulator CIA5 (CCM1). Massive impacts of CIA5 and CO2 on the transcriptome were observed, and genes with distinctive expression patterns presented a rich source of candidates for new CCM components.

Two second-site mutant suppressor strains of the "air dier ...


Phenotypic And Genetic Variation In An Apios Americana Breeding Collection; And Characterization Of The Hd-Zip Gene Family, Involved In Abiotic Stress Responses In Glycine Max, Vikas Belamkar Jan 2015

Phenotypic And Genetic Variation In An Apios Americana Breeding Collection; And Characterization Of The Hd-Zip Gene Family, Involved In Abiotic Stress Responses In Glycine Max, Vikas Belamkar

Graduate Theses and Dissertations

This dissertation has two main objectives: (1) morphological and genetic characterization of a little-studied edible legume native to North America, Apios americana; and (2) characterization of the soybean (Glycine max) homeodomain leucine zipper (HD-Zip) transcription factor family (involved in abiotic stress responses), and identification of candidate genes for dehydration and salt stress. In these projects, next generation sequencing (NGS) is evaluated as a tool for rapidly characterizing genetic variation (in Apios) and fine-scale genetic responses to abiotic stress (in soybean).

Apios, commonly called “potato bean,” is a nitrogen-fixing legume that is adapted to diverse climatic conditions of central and eastern ...


Elucidation Of A Bacteriophytochrome-Regulated Signal Transduction Pathway In Pseudomonas Syringae That Contributes To Leaf Colonization, Virulence, And Swarming Motility, Regina S. Mcgrane Jan 2015

Elucidation Of A Bacteriophytochrome-Regulated Signal Transduction Pathway In Pseudomonas Syringae That Contributes To Leaf Colonization, Virulence, And Swarming Motility, Regina S. Mcgrane

Graduate Theses and Dissertations

Plant-associated bacteria encounter a range of stressful environmental conditions when colonizing leaf surfaces. To adapt to these harsh conditions bacteria sense and respond to environmental signals. Within the last two decades, photoreceptors that respond to specific wavelengths of light through associated chromophores have been discovered with increasing frequency in non-photosynthetic bacteria, including those associated with plants. Their presence suggests that fluctuations in light may serve as a cue to regulate bacterial adaptations. The foliar plant pathogen Pseudomonas syringae is unusual among heterotrophic bacteria because it encodes three photoreceptors, two red- and/or far-red light-sensing bacteriophytochromes and a blue light-sensing LOV ...


Regulation Of Shoot Development In Maize Via Brassinosteroid Signaling, Gokhan Kir Jan 2015

Regulation Of Shoot Development In Maize Via Brassinosteroid Signaling, Gokhan Kir

Graduate Theses and Dissertations

Brassinosteroids (BR) are a class of phytohormones with many important roles in plant growth and development. Compared to other model organisms BR signaling is poorly understood in maize. To study BR signaling's role in maize growth and development we suppressed two members of the BR signaling pathway, BRI1 and BIN2, by RNAi approach. BLAST searches and phylogenetic analyses suggested that there are two BRI1 copies and three BRI1-like genes (BRL) homologs in maize. bri1b, which is located on chr 5, was incomplete in databases, but via subsequent cloning and sequencing was found to be an intact and expressed gene ...


Genome-Wide Association Studies To Dissect The Genetic Architecture Of Yield-Related Traits In Maize And The Genetic Basis Of Heterosis, Jinliang Yang Jan 2014

Genome-Wide Association Studies To Dissect The Genetic Architecture Of Yield-Related Traits In Maize And The Genetic Basis Of Heterosis, Jinliang Yang

Graduate Theses and Dissertations

This dissertation includes a general introduction (Chapter 1), three journal manuscripts (Chapters 2 to 4) and a section of general conclusions (Chapter 5). The paper in Chapter 2, which compares three statistical approaches for conducting GWAS and identifies the genetic architecture controlling for KRN trait, has been submitted for publication. I made major contributions include designing and performing the experiments, analyzing data and writing the manuscript under the guidance of Dr. Schnable. Dr. Nettleton and Dr. Dekkers provided technical support and conceptual advice for this work. The paper in Chapter 3, which investigates the modes of inheritance of trait-associated variants ...


Function Of Class One Nonsymbiotic Plant Hemoglobins, Xiaoguang Wang Jan 2014

Function Of Class One Nonsymbiotic Plant Hemoglobins, Xiaoguang Wang

Graduate Theses and Dissertations

Plants lack a circulatory system for oxygen. Thus hypoxia and anoxia are potential problems for plants. Environmental factors like flooding can make such problems even worse. At hypoxia and anoxia conditions, both nitrogen metabolism enzymes and nonsymbiotic hemoglobins in plants are up-regulated. Meanwhile, nitrite and nitric oxide are accumulated. Two physiological roles of plant nonsymbiotic hemoglobins were proposed: 1) nitric oxide scavenging during plant hypoxia using NOD function involving ascorbate and monodehydroascorbate reductase; 2) dissimilatory nitrite reduction during plant hypoxia or anoxia cooperating with other factors (since plant hemoglobin itself cannot reduce nitrite to ammonium in vitro). This thesis includes ...


Genetic Dissection Of Canonical Models Of Maize Kernel Growth And Development, Kendra Ann Meade Jan 2012

Genetic Dissection Of Canonical Models Of Maize Kernel Growth And Development, Kendra Ann Meade

Graduate Theses and Dissertations

An understanding of the genetics of maize kernel growth and development will provide valuable insight into a complicated physiological process. The genetics of kernel growth and development is of interest not only to plant scientists who seek to understand the underlying molecular mechanism but also to plant breeders who seek to develop improved hybrids with faster growing, larger kernels. In order to better understand the genetics of kernel growth and development, biomass accumulation and moisture content were observed in a sample of hybrids and a set of doubled haploids derived from a cross of elite inbred lines and testcrossed to ...


Transcriptional Mechanisms Of Brassinosteroid Regulated Plant Growth And Stress Responses, Huaxun Ye Jan 2012

Transcriptional Mechanisms Of Brassinosteroid Regulated Plant Growth And Stress Responses, Huaxun Ye

Graduate Theses and Dissertations

Plant Steroid hormones, Brassinosteroids (BRs), play important roles in plant growth, development and responses to various stresses. BR signal through receptor BRI1 and BAK1 and a series signaling intermediates to control the activities of BES1/BZR1 family transcription factors that control the expression of thousands of genes, half of which are induced and the other half repressed by BR. While BES1 is known to activate BR-induced genes by itself or cooperating with co-activators, such as transcription factors, histone modification enzymes and transcription elongation factors, how BES1 mediates the BR-repressed gene expression is not known. In chapter Ⅱ, MYBL2, a small ...


Structural Variation In The Maize Genome, Kai Ying Jan 2012

Structural Variation In The Maize Genome, Kai Ying

Graduate Theses and Dissertations

Whole-genome array-based comparative genomic hybridization (aCGH) was used to study structural variation between two elite maize inbred lines, B73 and Mo17. Several hundred Copy Number Variants (CNVs) as well as several thousands of Present Absent Variants (PAVs) were discovered. This high level of structural variation among haplotypes is unprecedented among higher eukaryotes. Haplotype-specific PAVs that encompass hundreds of single-copy, expressed genes may contribute to heterosis and the extraordinary phenotypic diversity of this important crop. aCGH can be also used for genotyping complex genomes, such as that of maize. Approximately 200,000 oligonucleotide probes whose hybridization signals exhibit significant differences between ...


Agronomic, Seed Traits And Oleate Stability Of Soybean Lines Containing The High-Oleate Transgene Dp-305423-1 And The Molecular Characterization Of The Genomic Region Flanking The High-Oleate Transgene, Jordan Dustin Spear Jan 2012

Agronomic, Seed Traits And Oleate Stability Of Soybean Lines Containing The High-Oleate Transgene Dp-305423-1 And The Molecular Characterization Of The Genomic Region Flanking The High-Oleate Transgene, Jordan Dustin Spear

Graduate Theses and Dissertations

To improve the oxidative stability of soybean [Glycine max (L.) Merr.] oil, it is desirable to increase the percentage of the monounsaturated fatty ester oleate. By altering the endogenous FAD2-1gene in soybean, oleate concentrations of greater than 750 g kg-1 can be obtained. From a commercial perspective, it is important to understand the influence of this genetic alteration on agronomic and seed traits, as well as the stability of the increased oleate concentration across a range of environments.

Objective one of my research was to evaluate the influence of the DP-305423-1 high-oleate (HO) transgene on agronomic and seed ...