Pea aphids, expert survivors of the insect world, appear to lack major biological defenses, according to the first genetic analysis of their immune system.
"It's surprising," says Emory biologist Nicole Gerardo, who led the study, published this week in Genome Biology. "Aphids have some components of an immune system, but they are missing the genes that we thought were critical to insect immunity."
Pea aphids are major agricultural pests and also important biological models for studies of insect-plant interactions, symbiosis, virus vectoring and genetic plasticity. These resilient insects thrive despite a host of enemies, including parasitic wasps, lady bugs, fungal pathogens and frustrated farmers and gardeners the world over.
The immune-system analysis is among a group of findings being published this month as part of the International Aphid Genomics Consortium, which recently published the full sequence of the pea aphid genome, and sponsored dozens of in-depth analyses of different areas of the sequence. Gerardo served as a project leader for the consortium, in addition to heading the immune system study.
"This is the first look at the genome of a whole group of insects we know little about," says Gerardo, an evolutionary biologist who focuses on host-parasite interactions.
All insects previously sequenced, including flies and bees, belong to a group that undergoes metamorphosis. Pea aphids, however, belong to an insect group known as basel hemimetablous meaning they are born looking like tiny adults.
"We went into this expecting to find the same set of immune-system genes that we've seen in the genomes of flies, mosquitoes and bees," Gerardo says. "Given these missing genes, it seems that aphids have a weak immune system. Our next step is to figure out how they protect themselves."
One hypothesis is that aphids may compensate for their lack of immune defenses by focusing on reproduct
|Contact: Beverly Clark|