Showing 31 - 40 of 63 Items
Investigating the Impacts of Drought on Turfgrass (Festuca arundinacea) Chlorophyll-a Fluorescence Emission
Date: 2024-01-01
Creator: Ayanna S Hatton
Access: Open access
- When photons from sunlight are absorbed by plants, they can take paths of photosynthesis, fluorescence, or energy dissipation. Instruments to quantify fluorescence have expanded in scale to allow measurements from satellites and flux towers using Solar-Induced Chlorophyll Fluorescence (SIF). Studies have found a positive correlation between SIF and gross primary productivity (GPP; representative of photosynthesis), suggesting SIF is a proxy for GPP. This conclusion encourages the use of SIF to inform decisions about carbon budgets and responding to climate change. Studies of fluorescence on the single-leaf scale have revealed that SIF measurements do not account for all variables nor is there an understanding of the impact of environmental factors, such as drought, on these measurements. In this project, tall fescue turfgrass was placed in one of four differing drought severities for 19 days. Leaf-level measurements of photosynthesis and pulse-amplitude modulated fluorescence were made, demonstrating stomatal closure and inhibition of photosynthesis. This physiological change caused greater photon allocation to energy dissipation. Changes in greenness and the utilization of photoprotective mechanisms such as senescence and anthocyanin accumulation were observed. This study has provided an understanding of the temporal, physiological, and visible impacts of drought on turfgrass to inform interpretations of SIF in future experiments. Caution is crucial in utilizing SIF as a proxy for GPP before further research into the impact of drought on SIF is completed.
Investigating the Impact of Helicobacter pylori Glycan Biosynthesis on Host Immune Response Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: William Joseph Surks
Access: Access restricted to the Bowdoin Community
Cell Adhesion in Arabidopsis thaliana Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2019-05-01
Creator: Natasha Ann Belsky
Access: Access restricted to the Bowdoin Community
The role of the ROG1 protein in pectin perception Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Divya Hoon
Access: Access restricted to the Bowdoin Community
Genetic Analysis of Adhesion Protein ELMO3 in Arabidopsis thaliana
Date: 2022-01-01
Creator: Garrison Asper
Access: Open access
- The Extracellular Matrix (ECM) between plant cells is vital for structure, development, and intercellular adhesion. A pectin rich layer in between cells, the middle lamella, is largely responsible for regulating the adhesive properties of adjacent plant cells. Homogalacturonan (HG) pectin, the most common, is synthesized in the Golgi and secreted into the ECM where it undergoes calcium crosslinking, increasing its adhesive properties. Mutations in proteins essential for HG synthesis can reveal a severe adhesion defective phenotype, where the hypocotyls of dark grown Arabidopsis exhibit cell sloughing, curling, and general disorganization. A family of five ELMO proteins are suspected to act as scaffolds for pectin biosynthesis enzymes. ELMO1 and ELMO4 mutants exhibit an adhesion deficient phenotype, and a double mutant provides evidence of redundancy in function between ELMO1 and ELMO2. ELMO1-GFP co-immunoprecipitated with enzymes required for HG synthesis indicating its role as a scaffold protein. Double mutants of the other ELMO homologues were created to determine if they exhibit functional redundancy, and ELMO1 and ELMO3 appear partially redundant. A gene deletion of ELMO3 was also created using the CRSPR/Cas9 system, resulting in two distinct elmo3 deletion alleles, which were phenotypically identical to the original elmo3-/- mutant. All adhesion defective phenotypes can be partially suppressed by altering the osmoticum and hence turgor that provides pressure on adhesive cells. Lastly, ELMO3-GFP was localized to the Golgi, the site of pectin biosynthesis, further supporting a common role of the ELMOs in pectin biosynthesis.
Reactions Responsible for Aging in Wood-Based Pyrolysis Oil: Synthesis and Characterization of a Coniferyl Alcohol Dimer
Date: 2021-01-01
Creator: Alejandro Garcia
Access: Open access
- The negative environmental impact and the diminishing supply of fossil fuels demand a renewable alternative. Pyrolysis oils produced from the decomposition of biomass, like wood, are a potential fuel substitute for energy production and a feedstock alternative for manufacturing value-added chemicals. The possibilities offered by pyrolysis oils are offset by oil instability. The oils contain reactive compounds, such as small aldehydes, conjugated aromatics, and acids that over time react and produce higher molecular mass products. This instability manifests as an increase in viscosity by a process referred to as aging. One chemical component, coniferyl alcohol, is proposed to react with formaldehyde under the acidic oil conditions to produce a dimer. In our lab, researchers have detected the coniferyl alcohol dimer in authentic oil samples and have simulated the reaction under conditions that removes the complexity of the pyrolysis oil matrix. This study focused on the synthesis, isolation, and characterization of the dimer structure by employing NMR analysis. GC/MS analysis of a successful synthesis of the dimer showed multiple dimers were produced, but there was one principal product. The NMR analysis of this dimer was used to elucidate the geometry, providing evidence that the product has E stereochemistry for the double bond and trans stereochemistry in the acetal ring. Confirmation of the principal structure provides support for the dimerization mechanism and will allow for future research to address instability of pyrolysis oils.
The Roles of ROG1, REM1, and REM2 in a WAK Mediated Pectin Response Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2015-05-01
Creator: Joshua A Benton
Access: Access restricted to the Bowdoin Community
Role of Polycomb group proteins in regulation of eyes absent gene expression in Drosophila melanogaster This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Joanne Du
Access: Embargoed
Investigating the effect of Fuc-O-NAP on the glycosylation of Helicobacter pylori Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: Panhasith Ung
Access: Access restricted to the Bowdoin Community
Examining the role of GRP and LIK1 in Wall Associated Kinase (WAK) perception of pectin in the plant cell wall
Date: 2017-01-01
Creator: Jack Ryan Mitchell
Access: Open access
- Wall associated kinases (WAKs) are cell membrane bound receptor kinases that bind pectin and pectin fragments (OGs).The binding of WAKs to pectin sends a growth signal required for cell elongation and plant development. WAKs bind OGs with higher affinity than native pectin and instead activate a stress response. Glycine rich proteins (GRPs) are secreted cell wall proteins of unknown function. Seven GRPs with 65% sequence similarity are coded on a 90kb locus of Arabidopsis chromosome 2. GRP3 and WAK1 have been shown to bind in vitro, but single null mutations have no discernible phenotype, suggesting that the GRPs are redundant. Low recombination frequency has made multiple mutations difficult to achieve, but in this thesis, CRISPR/Cas9 technology was used to induce deletions of the GRP locus. The promoters pYAO and pICU2 drove Cas9 expression in transformed Arabidopsis plants. The presence of a deletion and Cas9 were detected by PCR. While somatic mutations were induced, there was no inheritance of the GRP deletion, indicating that pYAO and pICU2 do not drive Cas9 to induce deletions in progenitor cells. LIK1 is a CERK1 interacting kinase implicated in mediating response to various microbe associated molecular patterns (MAMP) such as chitin, flagellin, and peptidoglycans. LIK1 exhibits a drastic increase in phosphorylation in response to OG treatment, making it a candidate for a co-receptor to WAK. T-DNA insertions to the 5’UTR of LIK1 were used to examine the effect of a lik1 mutation on the OG induced stress response. lik1/lik1 mutant seedlings were grown in the presence and absence of OGs, and RNA was isolated. qPCR was used on cDNA to examine FADLOX expression, a reporter for the transcriptional response to OGs. The lik1/lik1 mutant caused a reduction in the OG induced transcriptional response. However, increased LIK1 expression was associated with the T-DNA insertion indicating that LIK1 inhibits the WAK stress response pathway. Understanding the roles of GRP and LIK1 in moderating WAK mediated pathogenic response in Arabidopsis will enable a better understanding of plant resistance to pathogen invasion in the greater plant kingdom.