Location: Chemistry Research Unit
Title: Endogenous signals regulating herbivore-associated volatile emissions Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2012
Publication Date: N/A
Technical Abstract: Induced volatiles are a well-characterized response of maize plants to herbivory and contribute to defense through recruitment of natural enemies. Despite the importance of these volatiles, many questions remain regarding plant regulation of this response. While elicitor-induced production of jasmonic acid and ethylene is clearly involved, few other components of the maize signal transduction and amplification process have been identified. A search for additional components of maize herbivore defense signaling led to identification of a peptide which regulates responses against herbivores, and has thus been designated Herbivory Response Peptide (HRP). Expression of the gene encoding the HRP precursor is rapidly induced by Spodoptera exigua oral secretions. At application concentrations as low as 5 pMol per leaf, HRP stimulates production of both jasmonic acid and ethylene and activates expression of genes encoding proteins associated with defense against herbivory. These include proteinase inhibitors and biosynthetic enzymes for production of volatile terpenes and indole as well as benzoxazinoids. In accordance with gene expression data, plants treated with HRP emitted volatiles similar to those emitted by plants subjected to herbivory. HRP-treated plants also accumulated the highly reactive benzoxazinoid HDMBOA-Glc. The direct and indirect defenses induced by HRP were demonstrated to contribute to resistance against S. exigua through significant reduction of larval growth rates and attraction of Cotesia marginiventris parasitoids. HRP is active only in maize and other Poaceous plants. However, orthologs have been identified in other species and predicted HRP peptides from Solanaceous and Fabaceous plants induce herbivory-associated volatiles in their respective species. These studies indicate that HRP and HRP orthologs are a conserved mechanism across numerous plant species to regulate volatile emissions and other defenses against herbivory.