Dissertation
UNDERSTANDING THE PHYSIOLOGICAL ROLE OF AMINO ACID TRANSPORT IN PEA (PISUM SATIVUM L.) METABOLISM AND PERFORMANCE
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/118438
Abstract
Nitrogen is an essential nutrient that plants require in large amounts for successful growth and reproduction. Following nitrogen acquisition from the atmosphere or soil, temperate legumes such as pea (Pisum sativum L.) assimilate nitrogen to amino acids, which are used for metabolism, transiently stored, or transported via the vasculature to growing sinks such as developing leaves, fruits, and seeds. This research investigates the role of plasma membrane transporters in amino acid partitioning in pea plants and their importance for plant metabolism and development.
First, the role of a broad specific amino acid transporter in source to sink partitioning of nitrogen and plant productivity was analyzed using pea plants overexpressing (OE) amino acid permease 1 (PsAAP1) simultaneously in the phloem and developing cotyledons. Transgenic PsAAP1 OE plants demonstrated increased phloem and seed loading of amino acids, triggering improved seed development, and seed protein accumulation. Results further resolved that phloem loading of amino acids exerts regulatory control over nitrogen and carbon acquisition and metabolism.
Next, pea plants expressing a yeast cysteine/methionine transporter (MUP1) in the phloem and developing seeds were produced in the attempt to increase sulfur allocation to sinks and seed protein quality. Results showed that phloem levels of methionine, other amino acids and sucrose were increased, while delivery of these metabolites to individual seeds, as well as seed protein amounts were unchanged. Furthermore, the MUP1 plants produced more shoot biomass and higher seed yields than wild-type, supporting that changes in source to sink allocation of organic sulfur, nitrogen, and carbon promotes sink development in MUP1 plants. Finally, the function of pea amino acid permease 6 (PsAAP6) in organic nitrogen export from root nodules was examined. Localization studies resolved that PsAAP6 is expressed in the nodule cortex cells. Repression of PsAAP6 demonstrated that the transporter is essential for amino acid translocation from nodules to the shoot and roots. However, transporter activity did not affect biological nitrogen fixation and nodule metabolism, suggesting that pea nodule function is regulated by the shoot nitrogen status, rather than nodule nitrogen levels and/or partitioning processes.
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Details
- Title
- UNDERSTANDING THE PHYSIOLOGICAL ROLE OF AMINO ACID TRANSPORT IN PEA (PISUM SATIVUM L.) METABOLISM AND PERFORMANCE
- Creators
- Matthew G Garneau
- Contributors
- Mechthild Tegeder (Advisor)John Browse (Committee Member)Andrew McCubbin (Committee Member)Michael Knoblauch (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 173
- Identifiers
- 99900581714101842
- Language
- English
- Resource Type
- Dissertation