Insect herbivores selectively suppress the HPL branch of the oxylipin pathway in host plants (original) (raw)

Insect herbivores have developed a myriad of strategies to manipulate the defense responses of their host plants. Here we provide evidence that chewing insects differentially alter the oxylipin profiles produced by the two main and competing branches of the plant defensive response pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, responsible for wound-inducible production of jasmonates (JAs), and Green Leafy Volatiles (GLVs) respectively. Specifically, we used three Arabidopsis genotypes damaged by mechanical wounding or by insects of different feeding guilds (piercing aphids, generalist chewing caterpillars and specialist chewing caterpillars). We established that emission of GLVs is stimulated by wounding incurred mechanically or by aphids, but the release of these volatiles is constitutively impaired by both generalist and specialist chewing insects. Simultaneously however, these chewing herbivores stimulated JA production, demonstrating targeted insectsuppression of the HPL branch of the oxylipin pathway. Employment of lines engineered to express HPL constitutively, in conjunction with qRT-PCR-based expression analyses, established a combination of transcriptional and posttranscriptional reprogramming of the HPLpathway genes as the mechanistic basis of insect-mediated suppression of the corresponding metabolites. Feeding studies alluded to potential evolutionary advantage of suppressing GLV production as caterpillars preferably consumed leaf tissue from plants that had not been primed by these volatile cues. Feussner, I. and Fauconnier, M.L. (2009) Attacks by a piercing-sucking insect (Myzus persicae Sultzer) or a chewing insect (Leptinotarsa decemlineata Say) on potato plants (Solanum tuberosum L.) induce differential changes in volatile compound release and oxylipin synthesis. Journal of experimental botany, 60, 1231-1240. Halitschke, R. and Baldwin, I.T. (2003) Antisense LOX expression increases herbivore performance by decreasing defense responses and inhibiting growth-related transcriptional reorganization in Nicotiana attenuata. Plant J, 36, 794-807. Halitschke, R., Schittko, U., Pohnert, G., Boland, W. and Baldwin, I.T. (2001) Molecular interactions between the specialist herbivore Manduca sexta (Lepidoptera, Sphingidae) and its natural host Nicotiana attenuata. III. Fatty acid-amino acid conjugates in herbivore oral secretions are necessary and sufficient for herbivore-specific plant responses. Plant Physiol, 125, 711-717.