Graduate Student University of Washington Seattle, Washington
Body of Abstract: Plant defense responses to pests and pathogens are mediated by highly variable immune receptor gene families. We recently identified Inceptin Receptor (INR), a legume-specific receptor which detects In11, a ubiquitous 11-amino acid peptide HAMP in the oral secretions of Lepidopteran larvae (caterpillars). In11 elicits strong anti-herbivore direct and indirect defenses on cowpea, common bean, mung bean, and other legumes, but is inactive on all tested soybean varieties. Comparative genomic analysis revealed that INR is specific to the ~28 my old tribe of Phaseoloid legumes, but is absent in the subtribe Glycininae which includes wild, perennial, and cultivated soy (Glycine sp.), suggesting recent secondary loss-of-function and loss of In11 recognition. We hypothesized that restoration the missing INR immune receptor would enhance soybean responses to herbivory. Transgenic lines of Williams 82 (WT) soybean expressing INR from common bean (Phaseolus vulgaris) restored In11 responsiveness measured by rapid In11-induced release of the defense hormone ethylene. Beet armyworm (Spodoptera exigua) larvae reared on a T1 line (segregating for INR) gained 15% less weight than on a separate line lacking the transgene. We will report on ongoing experiments to measure both direct and indirect defenses to herbivory in INR-transgenic soybean lines, including analysis of In11-induced specialized metabolites and plant volatiles. INR provides a potential defense trait for recruitment of natural enemies and induction of endogenous inducible defenses, to augment Bt-based transgenic resistance to Lepidopteran pests.