Researchers Decipher Aphid Genome

Aphids are common pests of crops and ornamental plants. They feed exclusively on sugar-rich plant phloem sap by inserting their mouthparts into sieve elements, the primary food conduits of plants. Aphids cost farmers hundreds of millions of dollars annually by inflicting damage both through the direct effects of feeding and by vectoring debilitating plant viruses. In addition to their importance as agricultural pests, aphids are also important biological models for studies of insect-plant interactions, symbiosis, virus vectoring, and the developmental causes of extreme phenotypic plasticity.

An international consortium has published the whole genome sequence of the pea aphid Acyrthosiphon pisum. Reporting in the journal PLoS Biology, members of the International Aphid Genomics Consortium said they found extensive gene duplication in more than 2000 gene families as well as loss of evolutionarily conserved genes including genes involved in the IMD immune pathway, selenoprotein utilization, purine salvage, and the entire urea cycle. The 464 Mb aphid genome contains all genes required for epigenetic regulation by methylation. The researchers also found that the genes encoding the synthesis of a number of essential amino acids are distributed between the genomes of the pea aphid and its symbiont, Buchnera aphid cola.

"We found that the interaction of the pea aphid with its bacterial symbiont is far more intimate than anyone had previously envisioned," says Alex Wilson, professor at the University of Miami and member of the research team. "We hypothesize, based on the genome sequence that they each compensate for the evolutionary loss of genes by shuffling essential metabolic products between them. Gene loss between the two partners is so extensive that neither one can live without the other."

The paper is available at http://dx.doi.org/10.1371/journal.pbio.1000313