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Role of plant elicitor peptides and phytoalexins in enhancing maize resistance to Aspergillus flavus infection.
A. HUFFAKER (1), J. Sims (1), S. Christensen (1), E. A. Schmelz (1). (1) USDA-ARS CMAVE, Gainesville, FL, U.S.A.

Maize responds to pests and pathogens with complex defense responses. To facilitate effective breeding for pest and pathogen resistance, we’re elucidating cellular and molecular functions of regulatory and metabolic components of these maize defense responses. Our studies of regulatory components have focused on a family of peptide signals (ZmPeps) and their cognate receptors (ZmPEPRs) that regulate maize immunity. One of these, ZmPep1, triggers synthesis of plant defense phytohormones and induces expression of genes encoding pathogenesis-related proteins. ZmPep1 also promotes accumulation of the maize defense chemical HDMBOA-Glc. Treatment of maize plants with ZmPep1 prior to inoculation enhances resistance to fungal pathogens. A second peptide, ZmPep3, induces plant resistance responses against Lepidopteran herbivores associated with spread of mycotoxin-producing fungal pathogens. ZmPep3 stimulates expression of proteinase inhibitor genes and emission of volatiles that attract natural enemies of herbivorous pests. We’ve also discovered two families of fungal-induced terpenoid phytoalexins that accumulate at the plant pathogen interface, the kauralexins and zealexins. Several of these terpenoids have antimicrobial activity and we’re examining their effects on aflatoxin production. We aim to provide understanding of molecular processes regulating maize defense and new strategies for enhancing resistance to pests, disease and mycotoxin accumulation.

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