Project description:In most aphid species, facultative parthenogenetic reproduction allows rapid growth and formation of large single-genotype colonies. Upon predator attack, individual aphids emit an alarm pheromone to warn the colony of this danger. (E)-beta-farnesene (EBF) is the predominant constituent of the alarm pheromone in Myzus persicae (green peach aphid) and many other aphid species. Continuous exposure to alarm pheromone in aphid colonies raised on transgenic Arabidopsis thaliana plants that produce EBF leads to habituation of the aphid population. Whereas naïve aphids are repelled by EBF, habituated aphids show no avoidance response. Individual aphids from the habituated colony can revert back to being EBF-sensitive in three generations, indicating that this behavioral change is not caused by a genetic mutation. Instead, DNA microarray experiments comparing gene expression in naïve and habituated aphids treated with EBF demonstrate an almost complete desensitization in the transcriptional response to EBF. Furthermore, EBF-responsive aphids, but not habituated aphids show significantly lower reproduction in the presence of EBF. Although both naïve and habituated aphids emit EBF upon damage, EBF-responsive aphids display a higher survival rate in the presence of coccinellid predators and thus outperform habituated aphids that do not show an avoidance response. These results provide direct evidence that aphid perception of conspecific alarm pheromone aids in predator avoidance and thereby bestows fitness benefits in survivorship and fecundity. Although habituated M. persicae have equal fecundity on control and EBF-producing plants, such transgenics may have practical applications in agriculture because of increased predation of habituated aphids. Log fold-changes (LogFC) were computed and contigs with P-values ≤ 0.05 were considered to be differentially expressed (see Supplementary file at foot of this record).
