sometimes before the birth of the mother herself, so that females
can end up carrying both their daughters and their granddaughters within them. This telescoping of generations promotes short
generation times, allowing aphid colonies to rapidly exploit new
resources. Like other hemimetabolous insects, aphids undergo an
incomplete metamorphosis from juvenile to adult stages.
Here we present the genome sequence of the pea aphid,
Acyrthosiphon pisum. This aphid, which is widely used in laboratory
studies, attacks legume crops (Fabaceae) and is closely related to
important crop pests, including the green peach aphid (Myzus
persicae) and the Russian wheat aphid (Diuraphis noxia) [7]. This first
published hemimetabolous genome, coupled with the genomes of
its obligate and facultative bacterial symbionts [8,9,10], provides a
strong foundation for exploring the genetic basis of coevolved
symbiotic associations, of host plant specialization, of insect-plant
interactions, and of the developmental causes of extreme
phenotypic plasticity. We first provide an overview of the general
features of the pea aphid genome and then review findings of
manual gene annotation efforts focused on genes related to
symbiosis, insect-plant interactions, and development. Additional
findings from these annotation projects can be found in multiple
companion papers [8,11–39].