Browsing by Author "Price, Michelle B."
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- Analysis of T-DNA alleles of flavonoid biosynthesis genes in Arabidopsis ecotype ColumbiaBowerman, Peter A.; Ramirez, Melissa V.; Price, Michelle B.; Helm, Richard F.; Winkel, Brenda S. J. (2012-09-04)BACKGROUND: The flavonoid pathway is a long-standing and important tool for plant genetics, biochemistry, and molecular biology. Numerous flavonoid mutants have been identified in Arabidopsis over the past several decades in a variety of ecotypes. Here we present an analysis of Arabidopsis lines of ecotype Columbia carrying T-DNA insertions in genes encoding enzymes of the central flavonoid pathway. We also provide a comprehensive summary of various mutant alleles for these structural genes that have been described in the literature to date in a wide variety of ecotypes. FINDINGS: The confirmed knockout lines present easily-scorable phenotypes due to altered pigmentation of the seed coat (or testa). Knockouts for seven alleles for six flavonoid biosynthetic genes were confirmed by PCR and characterized by UPLC for altered flavonol content. CONCLUSION: Seven mutant lines for six genes of the central flavonoid pathway were characterized in ecotype, Columbia. These lines represent a useful resource for integrating biochemical and physiological studies with genomic, transcriptomic, and proteomic data, much of which has been, and continues to be, generated in the Columbia background.
- Functional Analysis of Plant Glutamate ReceptorsPrice, Michelle B. (Virginia Tech, 2013-10-02)The plant glutamate receptors (GLRs) are homologs of mammalian ionotropic glutamate receptors (iGluRs) and are hypothesized to be potential amino acid sensors in plants. Since their first discovery in 1998, the members of plant GLRs have been implicated in diverse processes such as C/N ratio sensing, root formation, pollen germination and plant-pathogen interaction. However, the exact properties of these channels, such as the spectrum of ligands, ion specificities, and subunit compositions are still not well understood. It is well established that animal iGluRs form homo- or hetero-tetramers in order to form ligand-gated cation channels. The first aspect of this research was to determine if plant GLRs likewise require different subunits to form functional channels. A modified yeast-2-hybrid system approach was initially taken and applied to 14 of the 20 AtGLRs to identify a number of candidate interactors in yeast. Forster resonance energy transfer (FRET), which measures the transfer of energy between interacting molecules, was performed in mammalian cells to confirm interaction between a few of those candidates. Interestingly, despite an abundance of overlapping co-localization between heteromeric combinations, only homomeric interactions were identified between GLRs 1.1 and 3.4 in HEK293 cells. Further, amino acids have been implicated in signaling between plants and microbes, but the mechanisms for amino acid perception in defense responses are far from being understood. Recently it was demonstrated that calcium responses initiated by bacterial and fungal microbe-associated molecular patterns (MAMPs) were diminished in seedlings treated with known agonists and antagonists of mammalian iGluRs, suggesting potential roles of GLRs in pathogen responses. Analysis of publicly available microarray data shows altered gene expression of a sub-fraction of GLRs in response to pathogen infection and bacterial elicitors. Thus, the second goal of my PhD research was aimed at determining whether GLRs are involved in the interaction between plants and pathogens. Gene expression changes of a number of candidate GLRs as well as pathogen growth was examined in response to the plant pathogen Pseudomonas syringae pv. tomato DC3000. Interestingly, single gene and multi-gene deficient plants responded differently with regards to pathogen susceptibility, likely as a result of functional compensation between GLRs.
- Glutamate receptor homologs in plants: functions and evolutionary originsPrice, Michelle B.; Jelesko, John G.; Okumoto, Sakiko (Frontiers, 2012)The plant glutamate-like receptor homologs (GLRs) are homologs of mammalian ionotropic glutamate receptors (iGluRs) which were discovered more than 10 years ago, and are hypothesized to be potential amino acid sensors in plants. Although initial progress on this gene family has been hampered by gene redundancy and technical issues such as gene toxicity; genetic, pharmacological, and electrophysiological approaches are starting to uncover the functions of this protein family. In parallel, there has been tremendous progress in elucidating the structure of animal glutamate receptors (iGluRs), which in turn will help understanding of the molecular mechanisms of plant GLR functions. In this review, we will summarize recent progress on the plant GLRs. Emerging evidence implicates plant GLRs in various biological processes in and beyond N sensing, and implies that there is some overlap in the signaling mechanisms of amino acids between plants and animals. Phylogenetic analysis using iGluRs from metazoans, plants, and bacteria showed that the plant GLRs are no more closely related to metazoan iGluRs as they are to bacterial iGluRs, indicating the separation of plant, other eukaryotic, and bacterial GLRs might have happened as early on as the last universal common ancestor. Structural similarities and differences with animal iGluRs, and the implication thereof, are also discussed.