Today an annotation of the pea aphid immune system has been published in Genome Biology by Nicole Gerardo and colleagues. This coincides with the publication of the draft pea aphid genome sequence from the International Aphid Genomics Consortium in PLoS Biology.

Due to its unusual process of metamorphosis the pea aphid provides interesting insights into insect development and, as a major vector of plant viruses and cause of crop damage, further understanding of pea aphid biology may lead to the development of control strategies. Pea aphids also display other fascinating biological properties, such as phenotypic plasticity, a lifecycle that alternates between parthenogenic and sexual reproduction, and they have co-evolved with symbiotic bacteria.

In their Genome Biology paper, which is also discussed in a Research Highlight in Genome Biology, Gerardo and colleagues perform an extensive manual annotation of the immune and stress response genes present in the pea aphid genome and they also analyse gene and protein expression in pathogen infected aphids to gain insights into how they respond to challenges to their immune system. They find that pea aphids lack many immune response genes found in other insect species and that their response to pathogen attack is more limited than in other insect species. These features may mirror those seen in other insects or they may be due to the unique biology of pea aphid and their relationship with symbiotic bacteria. Whatever the case turns out to be, the general view of insect immunity may not be as widely applicable as previously thought.