Induced expression of defence-related genes in barley is specific to aphid genotype

Understanding the mechanisms by which plants respond to attack is of great ecological and economic importance. When phloem-feeding insects feed they can influence the expression of defence-related genes in the plant. While it is well-documented that the genotype of the feeding insect can influence plant fitness traits, thus far the effect of insect genotype on the induction of defence-related genes in the plant has had relatively little attention. To investigate the molecular specificity of plant-insect interactions, the model plant Hordeum vulgare was exposed to four different genotypes of the aphid Sitobion avenae. When the plants were previously exposed to a specific aphid genotype, the population growth of other aphid genotypes was reduced. A global gene expression study of the barley genome showed that these effects can occur indirectly through physiological changes in the plant. We found 1018 transcripts to be differentially induced by different aphid genotypes, with some specific to one aphid genotype. This work identifies core and genotype-specific plant response genes to aphids and supports the notion that the genotypic composition of the herbivore population can trigger the transcription of different defence-related genes in the host plant, thus affecting the population structure of these herbivores and potentially the wider ecological community.