Aphids, Fungi, and Horizontal Gene Transfer – Now THAT is Sexy!

Ever wonder where those little red aphids got their color from?  No?  Well, in case you did, they manufacture their own carotenoids.  OK, carotenoids, who cares?  Lots of species use carotenoids to affect their color, what’s so special about aphids?!

Most animals get the carotenoids from their food.  But, the aphids manufacture them!  And that’s not all.  They flat-old stole the ability from fungi.  Yep, they stole it.  The little sucka’s incorporated part of the fungi genome into their own.

These sorts of “horizontal gene transfers
go on all the time in bacteria, but they’re supposedly a rarity among
more complex creatures like animals and plants. And yet, scientists
have recently documented several examples of such transfers. Rotifers smuggle genes from fungi, bacteria and plants. “Space Invader” genes have jumped across animals as diverse as lizards and bushbabies. One bacterium, Wolbachia, has even inserted its entire genome into that of a fruit fly. And parasites can transfer their genes to humans.

In most of these cases, it’s unclear whether the imported genes are
actually doing anything useful. But the story of the pea aphid, told by
Nancy Moran
and Tyler Jarvik, is very different. The colour of a pea aphid
determines the predators that target it. Ladybirds (one of their major
enemies) prefer to attack red aphids on green plants but parasitic
wasps are more likely to lay their eggs in green aphids, to fatal
effect. Colour clearly matters to an aphid, so here is a clear example
of a transferred gene shaping an obvious trait in its new host and in
doing so, shaping its evolution.


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