Partitioning of New Carbon as 11C in Nicotiana tabacum Reveals Insight into Methyl Jasmonate Induced Changes in Metabolism

• DOI: 10.1007/s10886-010-9835-x
• Publication Date: 2010-09-14T16:12:50Z
• Authors: Nils Hanik; Sara Gómez; Marcel Best; Michael Schueller; Colin M. Orians; Richard A. Ferrieri
• Keywords: 0301 basic medicine; 03 medical and health sciences

We examined the timeline by which methyl jasmonate (MeJA) reprograms new carbon partitioning into key metabolite pools. The radioactive isotope 11C (t1/2 20.4 min), administered to intact leaves of Nicotiana tabacum L. (cv Samsun) as 11CO2 gas enabled us to measure changes in new carbon partitioning into soluble sugar and amino acid pools of [11C]photosynthate. A 500 μM MeJA treatment resulted in a decrease in the [11C]soluble sugar pool and an increase in the [11C]amino acid pool after 4 h. This pattern was more pronounced 15 h after treatment. We also examined the timeline for 11C-partitioning into aromatic amino acid metabolites of the shikimate pathway. [11C]Tyrosine, [11C]phenylalanine and [11C]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, [11C]tyrosine and [11C]phenylalanine returned to baseline while [11C]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.