Chemical Ecology of Jasmonates as Signals for an Inducible Defense
Ian Baldwin Principal Investigator
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9507180 Baldwin Leaf damage by herbivores in Nicotiana sylvestris (Solanaceae) produces a damage signal which dramatically increases de novo nicotine synthesis in the roots. The increased synthesis leads to increases in whole-plant nicotine pools, which in turn make plants more resistant to further herbivore attack. Because signal production and the response to the signal occur in widely separated tissues, this whole-plant induced defense represents an ideal system in which to study the signal transduction cascade and how the biotic and abiotic environment influence this induced defense. It has been demonstrated that the damage signal has the characteristics of a slow-moving phloem-transported chemical cue and that jasmonic acid (JA), an octadecanoid- derived cyclopentanone, is an important component of the damage signal transduction pathway in this induced defense. In this project Dr. Baldwin will critically examine the hypothesis that wounding increases shoot JA pools which either directly through transport or indirectly through a systemin-like signal increase root JA pools, which, in turn stimulate root nicotine synthesis and increase whole-plant nicotine pools. To achieve this objective Dr. Baldwin will determine the chirality of the induced jasmonate pools in shoot and roots, examine the plant's nicotine responses to intermediates in the octadecanoid pathway and synthesize jasmonates in the native stereoconfigurations. By understanding the processes responsible for signal generation and transport it may be possible to understand how herbivores consume plants "stealthily" and apparently lessen the induced defenses activated by their feeding.