Contrary to popular belief, aphids are not just sap-sucking, plant-destroying enemies of agriculture. In fact, these pests are genetic pioneers that evolved two unique traits, according to a study that appears in the April 30 issue of the journal Science.
First, aphids are, so far, the only animal known to produce essential pigments known as carotenoids. The aphid's pigment-producing ability is unique to the animal kingdom. Other animals, including humans, that need carotenoids cannot produce these essentials themselves; instead, they must obtain carotenoids from food.
Why are carotenoids needed by many plants and animals? Because they provide vital support to varied functions, ranging from promoting immunity to reducing cell damage and providing color to fruits and vegetables. For example, carotenoids give tomatoes their red color and flamingoes their pink color. Carotenoids also determine whether aphids are red or green--a color distinction that influences their vulnerabiilty to predators and other threats.
As for the second unique trait, aphids probably acquired their carotenoid-producing ability through a rare, and perhaps unique, process: millions of years ago, aphids apparently "snatched" carotenoid-producing genes from a carotenoid-producing member of the fungi kingdom, and then snapped those snatched genes into their own genetic code.
Gene transfer between organisms is not itself a rare phenomenon. However, the fungi-to-aphid gene transfer is the only known gene transfer between members of the fungi kingdom and animal kingdom--which are so evolutionarily distant from one another that it was long thought that never the twain would genetically meet.
But by busting through kingdom barriers, aphids gained something akin to a "genetic magic wand" that empowered them to produce their own carotenoids. They were thereby freed of the need to scavenge for carotenoid-yielding foods. The result: one less chore
|Contact: Lily Whiteman|
National Science Foundation