The genome of the pea aphid (Acyrthosiphon pisum) has been sequenced for the first time, and entomologists and plant experts from Cornell, Ithaca College and the Boyce Thompson Institute for Plant Research (BTI) at Cornell have all played important roles in achieving the milestone.

Pea aphids feed on a variety of legume crops, notably alfalfa, which is used for forage in New York state. The pests not only compromise crop yields but also transmit 30 plant viruses. Conventional farmers use chemical sprays to control them.

The sequenced genome, published Feb. 23 in Public Library of Science--Biology, opens the door for researchers to better understand the biology of the aphid at the genetic and molecular levels. That may allow them to design new strategies to disrupt pathways and control these pests.

The effort to sequence the pea aphid genome has involved more than 100 collaborators from 30 institutions worldwide, with a concentration of experts in Ithaca, who worked to annotate specific groups of genes. The genome was sequenced at the Baylor College of Medicine's Human Genome Sequencing Center in Houston, Texas.

"In terms of the contribution to the study of aphid biology, this research is transformative," said Angela Douglas, Cornell's Daljit S. and Elaine Sarkaria Professor of Insect Physiology and Toxicology and one of the paper's co-authors. "The genome transforms our understanding of aphids to a completely new level. The fruits of this research should ripple to colleagues working at a very applied and extension level."

Local researchers played key roles in identifying aphid genes important to metabolism, transport, detoxification and plant virus transmission. The labs of Douglas; Georg Jander, an associate scientist at BTI; and Marina Caillaud, a biologist at Ithaca College, led the effort to annotate genes involved in metabolizing and transporting metabolites, including sugars, amino acids and purines (building blocks of DNA and RNA). These genes have evolved around a symbiotic relationship pea aphids share with bacteria that live in their tissues and are transmitted from mother to offspring, Douglas said. The bacteria make essential amino acids from plant sap and are so vital to the aphid that the insect dies when treated with antibiotics. With the genes now identified, researchers can adopt powerful new approaches to investigate the intimate relationship between bacteria and aphids.

"Once we understand these interactions, then we have an understanding to disrupt these interactions and control these aphid pests," Douglas said.

Members of the three laboratories also contributed to identifying pea aphid genes important in overcoming plant defenses, including enzymes in aphid saliva, and genes that play a crucial role in aphid transmission of viruses as they feed on plants.

"Our local contributions, three groups just here in Ithaca, reflect the strength of the collective expertise in this area," Douglas said.

The research was supported by the National Institutes of Health, National Science Foundation and U.S. Department of Agriculture.