Parker, Joel D., Parker, Karen M., Sohal, Barbara H. and Keller, Laurent
Decreased expression of Cu–Zn superoxide dismutase
1 in ants with extreme lifespan.
Proceedings of the National Academy of Sciences of the United States of America, 101, (10), . (doi:10.1073/pnas.0400222101).
Reactive oxygen species, the by-products of oxidative energy
metabolism, are considered a main proximate cause of aging.
Accordingly, overexpression of the enzyme Cu–Zn superoxide
dismutase 1 (SOD1) can lengthen lifespan of Drosophila melanogaster in the laboratory. However, the role of SOD1 as a main
determinant of lifespan has been challenged on the grounds that
overexpression might be effective only in compromised genetic
backgrounds. Moreover, interspecific comparisons show lower
levels of antioxidant activities in longer-lived species, suggesting
that life-span extension may evolve through less reactive oxygen
species generation from the mitochondria rather than higher
expression of SOD1. The tremendous variation in lifespan between
ant castes, ranging over 2 orders of magnitude, coupled with the
fact that all individuals share the same genome, provides a system
to investigate the role of SOD1 in the wild. We used the ant Lasius
niger as a model system, because queens can reach the extreme
age of 28 years, whereas workers and males live only 1–2 years and
a few weeks, respectively. We cloned SOD1 and found that
long-lived queens have a lower level of expression than workers
and males. Specific enzyme-activity assays also showed higher
SOD1 activity levels in males and workers compared with queens,
which had SOD1 activity levels similar to that of D. melanogaster.
Altogether, these data show that increased expression of SOD1 is
not required for the evolution of extreme lifespan, even in a system
in which differential gene expression is the only way to express
phenotypes with great lifespan differences.
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