Quantification, correlations and manipulations of wound-induced changes in jasmonic acid and nicotine in Nicotiana sylvestris
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Jasmonic acid (JA) is thought to be part of a signal-transduction pathway which dramatically increases de-novo nicotine synthesis in the roots and increases whole-plant (WP) nicotine pools in response to the wounding of the leaves in Nicotiana sylvestrisSpegazzini and Comes (Solanaceae). We report the synthesis of a doubly labeled JA ([1, 2-13C]JA) and use it as an internal standard to quantify by gas chromatography-mass spectrometry the changes in root and shoot JA pools in plants subjected to differing amounts of standardized leaf wounding. Wounding increased JA pools 10-fold locally in damaged leaves within 90 min and systemically in the roots (3.5-fold) 180 min after wounding. If JA functions as an intermediary between stimulus and response, quantitative relationships among the stimulus, JA, and the response should exist. To examine these relationships, we varied the number of punctures in four leaves and quantified both the resulting JA in damaged leaves after 90 min and the resulting WP nicotine concentration after 5 d. We found statistically significant, positive relationships among number of leaf punctures, endogenous JA, and WP nicotine accumulation. We used two inhibitors of wound-induced nicotine production, methyl salicylate and indole-3-acetic acid, to manipulate the relationships between wound-induced changes in JA and WP nicotine accumulation. Since wounding and the response to wounding occur in widely separated tissues, we applied inhibitors to different plant parts to examine their effects on the local and systemic components of this response. In all experiments, inhibition of the wound-induced increase in leaf JA 90 min after wounding was associated with the inhibition of the nicotine response 5 d after wounding. We conclude that wound-induced increases in leaf JA are an important component of this long-distance signal-transduction pathway.
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