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Figure 1
Alteration of the wound response of wild tobacco plants (Nicotiana attenuata) by Manduca caterpillar feeding. (A) Wounding of the leaf tissue results in a jasmonic acid burst, which is amplified by caterpillar feeding and the application of FACs from larval oral secretions to the wound. (B) Caterpillar attack, or the application of FACs to wounds, but not wounding alone induces the production of volatiles that function as predator attractants in the plants' indirect defense. (C) Caterpillar feeding and the application of their oral secretions to wounds cause an ethylene burst that (D) attenuates the wound- and jasmonic acid-induced accumulation of nicotine by suppressing the accumulation of transcripts for a key regulatory step in nicotine biosynthesis (pmt: putresine N-methyl transferase). The attenuation of the direct defense, nicotine, may be an adaptation to the feeding of a specialized herbivore that is able to tolerate high alkaloid concentrations and can potentially use them for its own defense. (E) Caterpillar attack and the addition of FACs to plant wounds also result in a transcriptional reconfiguration of the plant's wound-response. This reconfiguration consists of three temporal and spatial alterations. Addition of FACs antagonizes the wound-induced increase (W) of transcripts encoding threonine deaminase (TD), representing a type-I expression pattern that spreads systemically throughout the plant from the wound site. The wound-induced increase in transcripts in a type-IIa expression pattern (exemplified by PIOX: pathogen-induced peroxidase) is further amplified after application of FACs to wounds. In contrast, the genes with a type-IIb expression pattern are suppressed after wounding and further suppressed with the addition of FACs, as exemplified by the gene encoding the light harvesting complex subunit LHB C1. Both type IIa and IIb patterns are found only in the leaves directly suffering the herbivore attack (Redrawn from Kessler, A. and I. T. Baldwin (2002) Plant responses to insect herbivory: The emerging molecular analysis. Annual Review of Plant Biology (in press).)
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