Author Summary
Aphids are common pests of crops and ornamental plants.
Facilitated by their ancient association with intracellular
symbiotic bacteria that synthesize essential amino acids,
aphids feed on phloem (sap). Exploitation of a diversity of
long-lived woody and short-lived herbaceous hosts by
many aphid species is a result of specializations that allow
aphids to discover and exploit suitable host plants. Such
specializations include production by a single genotype of
multiple alternative phenotypes including asexual, sexual,
winged, and unwinged forms. We have generated a draft
genome sequence of the pea aphid, an aphid that is a
model for the study of symbiosis, development, and host
plant specialization. Some of the many highlights of our
genome analysis include an expanded total gene set with
remarkable levels of gene duplication, as well as aphidlineage-specific gene losses. We find that the pea aphid
genome contains all genes required for epigenetic
regulation by methylation, that genes encoding the
synthesis of a number of essential amino acids are
distributed between the genomes of the pea aphid and
its symbiont, Buchnera aphidicola,and that many genes
encoding immune system components are absent. These
genome data will form the basis for future aphid research
and have already underpinned a variety of genome-wide
approaches to understanding aphid biology.