Abstract
BackgroundIn the face of changing environmental conditions, the mechanisms underlying stress responses in diverse organisms are of increasing interest. In vertebrates, Drosophila, and Caenorhabditis elegans, FoxO transcription factors mediate cellular responses to stress, including oxidative stress and dietary restriction. Although FoxO genes have been identified in early-arising animal lineages including sponges and cnidarians, little is known about their roles in these organisms.Methods/Principal FindingsWe have examined the regulation of FoxO activity in members of the well-studied cnidarian genus Hydra. We find that Hydra FoxO is expressed at high levels in cells of the interstitial lineage, a cell lineage that includes multipotent stem cells that give rise to neurons, stinging cells, secretory cells and gametes. Using transgenic Hydra that express a FoxO-GFP fusion protein in cells of the interstitial lineage, we have determined that heat shock causes localization of the fusion protein to the nucleus. Our results also provide evidence that, as in bilaterian animals, Hydra FoxO activity is regulated by both Akt and JNK kinases.ConclusionsThese findings imply that basic mechanisms of FoxO regulation arose before the evolution of bilaterians and raise the possibility that FoxO is involved in stress responses of other cnidarian species, including corals.
Highlights
In bilaterian animals, members of the FoxO family of transcription factors are well-known for their roles in cellular responses to environmental and physiological stress
These findings imply that basic mechanisms of FoxO regulation arose before the evolution of bilaterians and raise the possibility that FoxO is involved in stress responses of other cnidarian species, including corals
To address the question of whether FoxO proteins are involved in stress responses in cnidarians, we focused on the cnidarian genus Hydra
Summary
Members of the FoxO family of transcription factors are well-known for their roles in cellular responses to environmental and physiological stress. In Drosophila, C. elegans, and mammalian cells, FoxO proteins increase resistance to oxidative stress [1,2,3,4]. Transcription of FoxO target genes increases under low nutrient conditions in Drosophila, C. elegans, and mammals [4,5,6] and during heat shock in C. elegans [7]. FoxO proteins mediate diverse cellular responses to stress. In C. elegans and mammals, FoxO proteins increase resistance to DNA damage [13,14,15]. Drosophila, and Caenorhabditis elegans, FoxO transcription factors mediate cellular responses to stress, including oxidative stress and dietary restriction. FoxO genes have been identified in early-arising animal lineages including sponges and cnidarians, little is known about their roles in these organisms
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