Characterization of the Arabidopsis glutamine dumper1 mutant reveals connections between amino acid homeostasis and plant stress responses

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dc.contributor.authorYu, Shien
dc.contributor.committeechairPilot, Guillaumeen
dc.contributor.committeememberOkumoto, Sakikoen
dc.contributor.committeememberGillaspy, Glenda E.en
dc.contributor.committeememberGrene, Ruthen
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen
dc.date.accessioned2016-10-07T06:00:22Zen
dc.date.available2016-10-07T06:00:22Zen
dc.date.issued2015-04-15en
dc.description.abstractAmino acids constitute the major organic form of transported nitrogen in plants, elements for protein synthesis, and precursors of many plant secondary metabolites, such as lignin, hormones, and flavonoids. Furthermore, amino acid metabolism lies at the crossroad of carbon and nitrogen metabolism. The Arabidopsis glutamine dumper1 (gdu1) mutant secretes glutamine from hydathodes, a phenotype caused by the overexpression of Glutamine Dumper1 (GDU1). GDU1 is a small transmembrane protein presents only in higher plants. The gdu1-1D mutant shows a pleiotropic phenotype: perturbed amino acid metabolism, tolerance to exogenous toxic concentrations of amino acids, elevated amino acid export, and activated stress/defense responses, lesions, and smaller rosettes. The biochemical function of GDU1 remains elusive. To better elucidate the biological processes leading to the complex Gdu1D phenotype, two approaches were conducted: (1) An ethyl methanesulfonate suppressor screening of the Gdu1D phenotype, which led to the isolation of intragenic mutations in GDU1 and mutations in the ubiquitin ligase LOG2 (Loss Of Gdu1D 2). Study of the intragenic mutations in GDU1 helped to characterize its structure-function relationships. Characterization of LOG2 showed that LOG2 interacts with GDU1 and is necessary for the Gdu1D phenotype. (2) The responses of the plant to the dexamethasone-induced expression of GDU1 were studied over time. This experiment identified major signaling pathways contributing to different components of the Gdu1D phenotype and the early events triggered by the perturbation of amino acid homeostasis. Our results showed that GDU1 overexpression first increases amino acid export, which is followed by amino acid imbalance and stress responses. This study sheds light on how amino acid imbalance interacts with various plant signaling pathways and stress responses, and suggests that LOG2 is involved in this process.en
dc.description.degreePh. D.en
dc.format.mediumETDen
dc.identifier.othervt_gsexam:5070en
dc.identifier.urihttp://hdl.handle.net/10919/73175en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectamino acid imbalanceen
dc.subjectamino acid homeostasisen
dc.subjectstress responseen
dc.subjectamino acid exporten
dc.subjectubiquitin ligaseen
dc.titleCharacterization of the Arabidopsis glutamine dumper1 mutant reveals connections between amino acid homeostasis and plant stress responsesen
dc.typeDissertationen
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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