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Title: Jasmonate Hormone: Regulating Synthesis of Reduced Carbon Compounds in Plants

Our original interest in understanding the role of jasmonate (JA) in regulating the final stages of stamen and pollen development led to our discovery of the JAZ repressors, and the molecular mechanism of JA action is now a second important focus of our research. The specific goals for this grant period are to: 1. Investigate the generation and clearance of the hormone with emphasis on the regulation of the OPR3 enzyme and the hydrolysis of JA-Ile. 2. Use dominant-negative and overexpression constructs to explore the role of the MYC5 transcription factor in initiating and regulating JA responses. 3. Investigate specific JAZ protein interactions that will help us to recognize and understand the extended network of processes, such as sulfur nutrition, that interface with JA signaling. The COI1 F-Box protein is a JA-Ile coreceptor and coi1 mutant plants lack JA responses. We have tested the possibility that sites of JA action can be probed by using tissue-specific promoters to drive expression of a COI1-YFP fusion protein in coi1 mutant plants deficient in stamen and pollen function. When we expressed COI1 behind a filament-specific promoter (from the DAD1 gene), filament elongation was restored but not anther dehiscence or pollen function. Three tapetummore » specific promoters, all failed to restore any of these three functions but, unexpectedly, a promoter active in the stomium and epidermal cells, restored both pollen function and anther dehiscence. Most importantly, our results demonstrate the power of promoter::COI1-YFP constructs in revealing the primary sites of JA-regulated gene expression that control developmental and other responses in neighboring tissues. We now plan to use this new tool to test current hypotheses about JA action in other organs of the plant. The MYC2, MYC3, and MYC4 proteins are the primary transcription factors initiating defense and root growth responses to JA signaling. However, transgenic plants overexpressing these proteins do not show any substantial reduction in shoot growth, even though they have increased expression of many JA-responsive genes. MYC5 is closely related to MYC2, MYC3, and MYC4 but has not previously been considered a candidate in JA signaling, in part because myc5 mutants exhibit no overt phenotype. However, when we overexpressed the MYC5 protein in wild-type Arabidopsis we got a surprising result. Whereas plants overexpressing MYC2 were similar in size to wild type, as observed previously, MYC5-OE plants were much smaller. This is an exciting discovery because it indicates that growth responses to JA may be controlled by a signaling pathway that is distinct from that pathway (or pathways) controlling secondary-product synthesis and defense.« less
  1. Washington State Univ., Pullman, WA (United States)
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Resource Type:
Technical Report
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Related Information: 1. Jewell, J.B. and Browse, J. 2016. Epidermal Jasmonate Perception is Sufficient for All Aspects of Jasmonate-Mediated Male Fertility in Arabidopsis. Plant J. 85:634-647.2. Havko, N.E., Major, I.T., Jewell, J.B., Attaran, E., Browse, J. and Howe, G.A. 2016. Control of Carbon Assimilation and Partitioning by Jasmonate: An Accounting of Growth–Defense Tradeoffs. Plants 5:7.3. Figueroa, P. and Browse, J. 2015 Male Sterility in Arabidopsis Induced by Overexpression of a MYC5-SRDX Chimeric Repressor. Plant J. 81:849-860.4. Thines, B., Mandaokar, A. and Browse, J. 2013 Characterizing Jasmonate Regulation of Male Fertility in Arabidopsis. Methods Mol. Biol. 1011:13-23.5. Bhosale, R., Jewell, J.B., Hollunder, J., Koo, A.J.K., Vuylsteke, M., Michoel, T., Hilson, P., Goossens, A., Howe, G.A., Browse, J. and Maere S. 2013 Predicting Gene Function from Uncontrolled Expression Variation Among Individual Wild-Type Arabidopsis Plants. Plant Cell. 25:2865-2877.6. Figuerora, P. and Browse, J. 2012 The Arabidopsis JAZ2 Promoter Contains a G-Box and Thymidine-Rich Module that are Necessary and Sufficient for Jasomonate-Dependent Activation by MYC Transcription Factors and Repression by JAZ Proteins. Plant Cell Physiol. 53:330-343.7. Routaboul, J.-M., Skidmore, C., Wallis, J.G. and Browse, J. 2011 Arabidopsis Mutants Reveal That Short- And Long-Term Thermotolerance Have Different Requirements For Trienoic Fatty Acids. J. Exp. Bot. 63:1435-1443. 8. Shyu, C., Figueroa, P., DePew, C.L., Cooke, T.F., Sheard, L.B., Moreno, J.E., Katsir, L., Zheng, N., Browse, J. and Howe, G.A. 2012 JAZ8 Lacks a Canonical Degron and Has an EAR Motif That Mediates Transcriptional Repression of Jasomonate Responses in Arabidopsis. Plant Cell. 24:536-550.9. Wager, A. and Browse, J. 2012 Social Network: JAZ Protein Interactions Expand Our Knowledge of Jasmonate Signaling. Front. Plant Sci. 3:41. Transcriptional Repression of Jasomonate Responses in Arabidopsis. Plant Cell. 24:536-550.
Research Org:
Washington State Univ., Pullman, WA (United States)
Sponsoring Org:
USDOE Chicago Operations Office (CO)
Country of Publication:
United States