FoxO and stress responses in the cnidarian Hydra vulgaris.
BACKGROUND
In 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.


RESULTS
We 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.


CONCLUSIONS
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.
Bridge
Diane
D
Department of Biology, Elizabethtown College, Elizabethtown, Pennsylvania, United States of America. bridged@etown.edu
Theofiles
Alexander G
AG
Holler
Rebecca L
RL
Marcinkevicius
Emily
E
Steele
Robert E
RE
Martínez
Daniel E
DE
D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003063:Cnidaria / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D051858:Forkhead Transcription Factors; D049452:Green Fluorescent Proteins; D051057:Proto-Oncogene Proteins c-akt; D048670:MAP Kinase Kinase 4