Suppression of a P450 hydroxylase gene in plant trichome glands enhances natural-product-based aphid resistance

Trichome glands on the surface of many higher plants produce and secrete ex udates affecting insects, microbes, and herbivores. Metabolic engineering o f gland exudation has potential for improving pest/disease resistance, and for facilitating molecular farming. We identified a cytochrome P450 hydroxy lase gene specific to the trichome gland and used both antisense and sense co-suppression strategies to investigate its function. P P450-suppressed tr ansgenic tobacco plants showed a greater than or equal to 41% decrease in t he predominant exudate component, cembratriene-diol (CBT-diol), and a great er than or equal to 19-fold increase in its precursor, cembratriene-ol (CBT -ol). Thus, the level of CBT-ol was raised from 0.2 to greater than or equa l to4.3% of leaf dry weight. Exudate from antisense-expressing plants had h igher aphidicidal activity, and transgenic plants with exudate containing h igh concentrations of CBT-ol showed greatly diminished aphid colonization r esponses. Our results demonstrate the feasibility of significantly modifyin g the natural-product chemical composition and aphid-interactive properties of gland exudates using metabolic engineering. The results also have impli cations for molecular farming.