The genome of the aphid Acyrthosiphon pisum

The genome of the aphid Acyrthosiphon pisum has been secuenciado for the International Consortium of the Genome of the Aphid (IAGC in his initials in English), a consortium formed by more than 50 groups of investigation of 16 countries.

The IAGC was created in Paris in June, 2003 to coordinate efforts and to promote the investigation on aphides to convert them into a biological reference model to molecular, cellular and biological scale at the same level as other insects it shaped whose genome has already been secuenciado.

Why A. pisum?

As other species that are part of the Project Genome of the Insects, the election of A. pisum has been based on his economic importance. This aphid is a parasite of leguminous plants that causes serious agricultural plagues and economic losses in the agriculture. The peculiarities of his vital cycle (rapid reproduction and existence of multiple forms) it turns him into a perfect model for studies on the interactions between plants and insects, symbiosis, vector of transmission of virus and genetic plasticity. It supports a symbiotic relation with the bacterium Buchnera aphidicola, which lives inside a few specializing cells through called bacteriocitos and with the one that has coevolved. Also, there is the first insect hemíptero (thumbtacks, cicadas and aphides) and the first one with partial metamorphosis (hemimetábolo) whose genome there is secuenciado.

Vital cycle of Acyrthosiphon pisum. During the spring and the summer, the females [F] reproduce asexualmente (parthenogenesis) giving place to a descent (females) áptera [To] or flutter [B] that also is reproduced asexualmente. The winged aphides, which can disperse to other plants, take place in conditions of overpopulation or stress. During the autumn, males take place ápteros and flutters of wings [D] and females ápteras [C] that are reproduced sexually and put eggs [And] that will give place in the spring to females ápteras [F]. The females they can be vivíparas (when the reproduction is asexual) and oviparous (when the reproduction is sexual).

Peculiarities of his genome

The sequence of the genome of A. pisum has given place to more than 30 scientific articles, many of them published in a special number of the magazine Insect Molecular Biology.

• A. Pisum has a genome haploide with approximately 464 million pairs of bases (nucleótidos), major than that of other insects, and four chromosomes. Although the article published in Plos Biology does not give a concrete number alleging that is necessary a more precise inventory, Stephen Richards, chief of the team that there is secuenciado the genome of the aphid, speech of 35.000 genes (the human genome has approximately 23.000), many of which are duplicated and others have no equivalence in other insects species.
• The genomes of A. pisum and B. aphidicola they are coordinated. Some metabolic routes are shared, the genome of the aphid presents genes of bacterial origin and the bacterium synthesizes nine amino acids that the aphid can neither produce also do not even nor obtain across his diet.
• Several genes of the immune system are absent, specifically those of the route IMD that they produce péptidos antibacterial like the cecropina and the defensina. This can be interpreted of two forms: the defenses absence opposite to bacterial infections could facilitate the symbiosis with bacteria or that his rapid reproductive cycle and his feeding (sap of plants) frees from bacteria diminished the selective pressure to support a costly immune system.
• Like herbivorous animal, it possesses an enzymes arsenal destoxificadoras. Nevertheless, his number is minor than, for example, the fruit fly, the mosquito Anopheles or the red beetle of the flour and major than that of the bee melífera.
• The peculiar vital cycle of the aphides, which alternates forms vivíparas with oviparous and winged forms with ápteras, can be facilitated by duplications in many genes related to his development.

Genome Sequence of the Pea Aphid Acyrthosiphon pisum The International Aphid Genomics Consortium. 2010. PLoS Biol 8 (2), e1000313. The International Aphid Genomics Consortium (2010). Genome Sequence of the Pea Aphid Acyrthosiphon pisum PLoS Biology, 8 (2) DOI: 10.1371/journal.pbio.1000313 AphidBase Base de datos of the genome of the aphid.