Title page for ETD etd-08092012-090201

Type of Document Master's Thesis
Author Vallabhaneni, Prashanthi
Author's Email Address vprash@vt.edu
URN etd-08092012-090201
Title Metabolomic approaches to understanding the auxin and ethylene response in Arabidopsis roots
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Winkel, Brenda S. J. Committee Chair
Helm, Richard Frederick Committee Member
Muday, Gloria K. Committee Member
Tholl, Dorothea B. C. Committee Member
  • Arabidopsis
  • metabolite analysis
  • flow injection electrospray mass spectrometry
  • auxin
  • ethylene
Date of Defense 2012-06-22
Availability unrestricted
Non-targeted metabolite profiling by liquid chromatography-mass spectrometry (LC-MS) was used to determine the metabolite responses of Arabidopsis roots to auxin or ethylene. Crosstalk between these hormones regulates many important physiological processes in plants, including the initiation of lateral root formation and the response to gravity. These occur in part through alterations in the levels of flavonoids, specialized plant metabolites that have been shown to act as negative regulators of auxin transport. However, much remains to be learned about auxin and ethylene responses at the level of the metabolome. LC-MS analysis showed that a number of ions changed in response to both hormones in seedling roots. Although classes of specialized metabolites such as flavonols and glucosinolates change in abundance in response to both auxin and ethylene, there was little overlap with regard to the specific metabolites affected. These data will be integrated with information from transcriptomic and proteomic experiments to develop framework models that connect phytohormones and specialized metabolism with specific physiological processes.

Previous studies by imaging techniques have shown that flavonols increase in response to both auxin and ethylene in the root elongation zone, but LC-MS showed that flavonols decreased in abundance in response to these hormones. Therefore a method was developed for targeted metabolite profiling of flavonols in individual root tips by flow injection electrospray mass spectrometry. This method uncovered spatial differences in metabolic profiles that were masked in analyses of whole roots or seedlings, and verified that flavonols increase in response to these hormones in root tips.

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