Overexpression and Down-Regulation of Barley Lipoxygenase LOX2.2 Affects Jasmonate-Regulated Genes and Aphid Fecundity.

Aphids are pests on many crops and depend on plant phloem sap as their food source. In an attempt to find factors improving plant resistance against aphids, we studied the effects of overexpression and down-regulation of the lipoxygenase gene in barley ( L.) on the performance of two aphid species. A specialist, bird cherry-oat aphid ( L.) and a generalist, green peach aphid ( Sulzer) were studied. overexpressing lines showed up-regulation of some other jasmonic acid (JA)-regulated genes, and antisense lines showed down-regulation of such genes. Overexpression or suppression of did not affect aphid settling or the life span on the plants, but in short term fecundity tests, overexpressing plants supported lower aphid numbers and antisense plants higher aphid numbers. The amounts and composition of released volatile organic compounds did not differ between control and overexpressing lines. Up-regulation of genes was similar for both aphid species. The results suggest that plays a role in the activation of JA-mediated responses and indicates the involvement of in basic defense responses.