Petunia hybrida PDR2 is involved in herbivore defense by controlling steroidal contents in trichomes
Sasse, J, Schlegerl, M, Borghi, L, Ullrich, F, Lee, M, Liu, GW, Giner, JL, Kayser, O, Bigler, L, Martinoia, E & Kretzschmar, T 2016, 'Petunia hybrida PDR2 is involved in herbivore defense by controlling steroidal contents in trichomes', Plant Cell Environment, vol. 39, no. 12, pp. 2725-2739.
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As a first line of defense against insect herbivores many plants store high concentrations of toxic and deterrent secondary metabolites in glandular trichomes. Plant Pleiotropic Drug Resistance (PDR)-type ABC transporters are known secondary metabolite transporters, and several have been implicated in pathogen or herbivore defense. Here, we report on Petunia hybrida PhPDR2 as a major contributor to trichome-related chemical defense. PhPDR2 was found to localize to the plasma membrane and be predominantly expressed in multicellular glandular trichomes of leaves and stems. Down-regulation of PhPDR2 via RNA interference (pdr2) resulted in a markedly higher susceptibility of the transgenic plants to the generalist foliage feeder Spodoptera littoralis. Untargeted screening of pdr2 trichome metabolite contents showed a significant decrease in petuniasterone and petuniolide content, compounds, which had previously been shown to act as potent toxins against various insects. Our findings suggest that PhPDR2 plays a leading role in controlling petuniasterone levels in leaves and trichomes of petunia, thus contributing to herbivory resistance.