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Convergent use of polyphenols by insects and plants.
Appel, Heidi1, 1
ABSTRACT- Polyphenols and polyphenol-protein complexes figure prominently in both plant and insect responses to enemies. In both cases, wounding or biochemical elicitors induce polyphenol synthesis and oxidative enzyme activity, both of which are required for most polyphenol action. Polyphenols are derived primarily from phenylalanine in plants via the shikimate pathway and from tyrosine in animals. Both groups of polyphenols are oxidized and polymerized by polyphenol oxidases (PPOs) and peroxidases (PODs). Once oxidized, they can form a variety of products, including covalent complexes with proteins and other compounds. These oxidation products are antimicrobial and participate in wound repair in both plants and animals. Transcriptional regulation of polyphenol-enzyme defense systems is much better known for plants than for insects. Similar polyphenols may also function as signals in analogous plant and animal systems, providing opportunities for plants and herbivores to manipulate each other. Examples may include insects that can suppress plant defenses, and plants that can interfere with insect immune responses. Plant and animal uses of polyphenol-enzyme systems are compared with those employed by microbes, and the implications for tritrophic ecological and evolutionary interactions are discussed.
KEY WORDS: polyphenols, tannins, plant-insect interactions, tritrophic interactions