Dissertation
Jasmonate Metabolism and Signaling in Abiotic Stress and Male Reproductive Development
Doctor of Philosophy (PhD), Washington State University
01/2014
Handle:
https://hdl.handle.net/2376/117977
Abstract
Jasmonic acid (JA) is a plant hormone with essential roles in reproductive development and in regulation of plant responses to multiple stresses. Very recently the isoleucine-conjugated derivative of jasmonic acid, jasmonoyl-isoleucine (JA-Ile), has been identified as the molecularly active form of the hormone. This information, coupled with the recent identification of the core jasmonate signaling module allows for productive reverse-genetic interrogation of mechanisms of JA-Ile inactivation. ILL6 was identified as an Arabidopsis gene whose expression is closely correlated with the Jasmonate ZIM-Domain (JAZ) genes, which encode essential components of the jasmonate co-receptor complex. Like the JAZ genes, ILL6 is rapidly induced by jasmonate treatment and wounding. ill6 mutant plants were identified and observed to be hypersensitive to jasmonate-mediated inhibition of root and leaf growth. In addition, these mutants accumulated significantly more wound-induced JA-Ile than wild type plants. Consistent with the similarity of the ILL6 protein to other hormone-amino acid conjugate hydrolases, ill6 mutant plants hydrolyzed substantially less exogenously-applied radiolabeled JA-Ile than did wild type plants. A cyp94b3 mutant that accumulates more JA-Ile than wild type was found to hydrolyze significantly more JA-Ile than wild type, and this increased JA-Ile hydrolysis was dependent on ILL6, indicating that JA-Ile rather than any other JA-Ile derived metabolite is the in vivo substrate for ILL6. In other experiments I confirmed previous reports that indicated increased jasmonate signaling in response to external sulfate deficiency. Importantly, an increased capacity for jasmonic acid biosynthesis was seen in sulfate-deprived plants, and jasmonate biosynthesis and perception mutants were found to be defective in senescence induced by sulfate-deficiency. Finally, I used tissue-specific complementation of the male-sterile jasmonate-insensitive mutant coi1 to interrogate in which tissues of the Arabidopsis stamen jasmonate perception is sufficient for male fertility. Complementation of jasmonate perception in the stamen epidermis using the WUSCHEL or COI1 promoters resulted in complete rescue of male fertility. This surprising result indicates the presence of a previously undiscovered cell non-autonomous signal triggered by JA-Ile perception in the anther epidermis to initiate pollen maturation. In summary this dissertation reports a novel pathway for JA-Ile inactivation, a novel role for JA signaling in sulfate-deficiency-induced senescence, and clarification of the essential site of perception in JA-mediated reproductive development.
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Details
- Title
- Jasmonate Metabolism and Signaling in Abiotic Stress and Male Reproductive Development
- Creators
- Jeremy Burke Jewell
- Contributors
- John Browse (Advisor)Michael Neff (Committee Member)Sanja Rojes (Committee Member)Hanjo Hellmann (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
- 160
- Identifiers
- 99900581845301842
- Language
- English
- Resource Type
- Dissertation