Journal
JOURNAL OF CHEMICAL ECOLOGY
Volume 36, Issue 10, Pages 1058-1067Publisher
SPRINGER
DOI: 10.1007/s10886-010-9835-x
Keywords
Methyl jasmonate; Plant defenses; Metabolic partitioning; Chemical signaling; Short-lived radiotracers; C-11; Nicotiana tabacum; Shikimate pathway
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Funding
- U.S. Department of Energy, Office of Biological and Environmental Research [DE-AC02-98CH10886]
- National Research Initiative of the USDA National Institute of Food and Agriculture [2007-35302-18351]
- German Academic Exchange Service (Deutscher Akademischer Austauschdienst=DAAD), Bonn
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We examined the timeline by which methyl jasmonate (MeJA) reprograms new carbon partitioning into key metabolite pools. The radioactive isotope C-11 (t(1/2) 20.4 min), administered to intact leaves of Nicotiana tabacum L. (cv Samsun) as (CO2)-C-11 gas enabled us to measure changes in new carbon partitioning into soluble sugar and amino acid pools of [C-11]photosynthate. A 500 mu M MeJA treatment resulted in a decrease in the [C-11]soluble sugar pool and an increase in the [C-11]amino acid pool after 4 h. This pattern was more pronounced 15 h after treatment. We also examined the timeline for C-11-partitioning into aromatic amino acid metabolites of the shikimate pathway. [C-11]Tyrosine, [C-11]phenylalanine and [C-11]tryptophan were elevated 1.5-fold, 12-fold and 12-fold, respectively, relative to controls, 4 h after MeJA treatment, while endogeneous pools were unchanged. This suggests that only new carbon is utilized during early stages of defense induction. By 15 h, [C-11]tyrosine and [C-11]phenylalanine returned to baseline while [C-11]tryptophan was elevated 30-fold, suggesting that MeJA exerts selective control over the shikimate pathway. Finally, we measured trans-cinnamic acid levels as a gauge of downstream phenolic metabolism. Levels were unchanged 4 h after MeJA treatment relative to controls, but were increased 2-fold by 15 h, indicating a lag in response of secondary metabolism.
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