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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

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Investigation Of Soybean Susceptibility To Soybean Aphids And How Aphids Affect Plant-Mediated Pest Interactions, Jessica Hohenstein Jan 2017

Investigation Of Soybean Susceptibility To Soybean Aphids And How Aphids Affect Plant-Mediated Pest Interactions, Jessica Hohenstein

Graduate Theses and Dissertations

The soybean aphid (Aphis glycines) is an important insect pest of soybean (Glycine max). Previously, jasmonic acid (JA) was shown to elicit effective plant defense responses against soybean aphids. However, aphids were able to attenuate wound- or JA-induced responses in infested leaves in the compatible interaction and the mechanism of suppression remained uncharacterized. We hypothesized that aphids induce a decoy pathway to suppress plant defense responses and showed that aphids exploit the abscisic acid (ABA) pathway to suppress JA-mediated signaling. Both endogenous and exogenous ABA suppressed the wound-induced JA response. Furthermore, aphid populations were significantly reduced in the absence of ...


A Genetic And Genomic Study Of Resistance To 4-Hydroxyphenylpyruvate Dioxygenase (Hppd) Inhibitor Herbicides In Amaranthus Tuberculatus (Waterhemp), Daniel Robert Kohlhase Jan 2016

A Genetic And Genomic Study Of Resistance To 4-Hydroxyphenylpyruvate Dioxygenase (Hppd) Inhibitor Herbicides In Amaranthus Tuberculatus (Waterhemp), Daniel Robert Kohlhase

Graduate Theses and Dissertations

Waterhemp (Amaranthus tuberculatus) is an agronomic weed found throughout the Midwestern United States. Without proper management waterhemp has the potential to cause yield losses up to 74% and 56% in maize (Zea mays L.) and soybean [Glycine max (L.) Merr.], respectively. There are various characteristics of waterhemp that contribute to increasing prevalence of waterhemp in agriculture including the ability to evolve herbicide resistance. There are six herbicide sites of action that have been evolved in waterhemp. In 2011, waterhemp was discovered to be resistant to p-hydroxyphenylpyruvate-dioxygenase (HPPD, EC 1.13.11.27) inhibitor herbicides. The objectives of my research were ...


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 ...


Identification And Characterization Of Cold-Responsive Genes In Perennial Ryegrass, Chunzhen Zhang Jan 2009

Identification And Characterization Of Cold-Responsive Genes In Perennial Ryegrass, Chunzhen Zhang

Graduate Theses and Dissertations

In this study, analysis of freezing-induced ion leakage revealed that freezing tolerance of the perennial ryegrass cv. Caddyshack was continuously increased from 1 d to 14 d of cold acclimation. About 3,000 quality ESTs were generated from two cDNA libraries that were constructed from cold-acclimated (CA) and nonacclimated (NA) perennial ryegrass cv. Caddyshack plant materials. Comparative analysis of EST indicated that over 60 EST groups were either increased or decreased three times or more in the CA library than in the NA library. Reverse transcriptase PCR (RT-PCR) analysis confirmed that the expression patterns for 19 out of the 23 ...


Evaluation Of The Expression Of Water Stress-Responsive Pseudomonas Syringae Genes During Plant Infection And In The Presence Of Low Osmotic Versus Low Matric Potential In Culture, Kelly Crowley Peterson Jan 2009

Evaluation Of The Expression Of Water Stress-Responsive Pseudomonas Syringae Genes During Plant Infection And In The Presence Of Low Osmotic Versus Low Matric Potential In Culture, Kelly Crowley Peterson

Graduate Theses and Dissertations

The purpose of these studies was to characterize bacterial gene expression changes within the intercellular plant environment during infection with Pseudomonas syringae pv. tomato DC3000 as well as during water stress in culture. Our goals were to measure gene expression of the osmoresponsive proU promoter during early plant infection, and to measure specifically osmotically and matrically-induced genes during upshock with NaCl or the nonpermeating compound PEG8000 which sequesters water, at -1 MPa. To accomplish our first goal of measuring gene expression in planta we employed proU-inaZ and proU-uidA reporter gene fusions, both of which were found to be limited due ...