In the study, published online Jan. 31 in the journal Aging, the researchers, led by postdoctoral scholar Chen-Tseh Zhu, describe experiments that confirm that the Hoppel transposon's presence positively affected life span and fertility in the flies. What they found is that the optimal case for those two traits was heterozygosity: one allele, or copy, of the Indy gene in a fly having the insertion and the other not having it.
Life span and fertility
The researchers measured the physiological effects of Hoppel by looking at flies from three different lines: one from Oahu gathered in 1950s, another from Captain Cook, Hawaii, gathered in 2007, and one with its origin in Hidalgo, Mexico, in 2005. Each line had some flies with at least one copy of Indy with Hoppel and some with no Hoppel in Indy.
The heterozygous females in these lines ended up laying about 10 percent more eggs than flies that had no Indy alleles with Hoppel. Flies for whom both Indy alleles had Hoppel laid the fewest eggs. This demonstrates that one Indy allele with Hoppel had a strong selective advantage in reproductive fitness, Helfand said.
For life span, flies that had Hoppel on at least one Indy allele lived considerably longer than flies with no Hoppel on either chromosome. For example, among one group of females, by day 60, more than 80 percent of heterozygotes, and about 80 percent with Hoppel on both alleles were still alive. For those without any Hoppel insertion, less than 60 percent were still buzzing about by day 60.
Indy and Hoppel
For all the prior lab work, researchers are still not completely sure how Indy works, with our without mutations such as the Hoppel insertion. The protein the gene encodes appears to help gate metabolically important small nutrients such as citrate in the cell cytoplasm. Mutations in the gene appea
|Contact: David Orenstein|