Natural polymorphism affecting learning and memory in Drosophila:
Knowing which genes contribute to natural variation^ in learning and memory would help us understand how differences^ in these cognitive traits evolve among populations and species.^ We show that a natural polymorphism at the foraging (for) locus,^ which encodes a cGMP-dependent protein kinase (PKG), affects^ associative olfactory learning in Drosophila melanogaster. In^ an assay that tests the ability to associate an odor with mechanical^ shock,
flies homozygous for one natural allelic variant of this^ gene (
(
for^R
) showed better short-term but poorer long-term memory^ than flies homozygous for another natural allele
for^s
). The^
for^s
allele is characterized by reduced PKG activity. We showed^ that
for^R
-like levels of both short-term learning and long-term^ memory can be induced in
for^s
flies by selectively increasing^ the level of PKG in the mushroom bodies, which are centers of^ olfactory learning in the fly brain. Thus, the natural polymorphism^ at for may mediate an evolutionary tradeoff between short- and^ long-term memory.
The respective strengths of learning performance^ of the two genotypes seem coadapted
with their effects on foraging^ behavior:
for^R
flies move more between food patches and so could^ particularly benefit from fast learning, whereas
for^s
flies^ are more sedentary, which should favor good long-term memory.
