title: Hydrogen peroxide and ecdysone in the cryoprotective dehydration strategy of Megaphorura arctica (Onychiuridae: Collembola).
abstract: The Arctic springtail, Megaphorura arctica, survives sub-zero temperatures in a dehydrated state via trehalose-dependent cryoprotective dehydration. Regulation of trehalose biosynthesis is complex; based in part on studies in yeast and fungi, its connection with oxidative stress caused by exposure of cells to oxidants, such as hydrogen peroxide (H₂O₂), or dehydration, is well documented. In this respect, we measured the amount of H₂O₂ and antioxidant enzyme activities (superoxide dismutases: copper, zinc--CuZnSOD and manganese containing--MnSOD, and catalase--CAT), as the regulatory components determining H₂O₂ concentrations, in Arctic springtails incubated at 5 °C (control) versus -2 °C (threshold temperature for trehalose biosynthesis). Because ecdysone also stimulates trehalose production in insects and regulates the expression of genes involved in redox homeostasis and antioxidant protection in Drosophila, we measured the levels of the active physiological form of ecdysone--20-hydroxyecdysone (20-HE). Significantly elevated H₂O₂ and 20-HE levels were observed in M. arctica incubated at -2 °C, supporting a link between ecdysone, H₂O₂, and trehalose levels during cryoprotective dehydration. CAT activity was found to be significantly lower in M. arctica incubated at -2 °C versus 5 °C, suggesting reduced H₂O₂ breakdown. Furthermore, measurement of the free radical composition in Arctic springtails incubated at 5 °C (controls) versus -2 °C by Electron Paramagnetic Resonance spectroscopy revealed melanin-derived free radicals at -2 °C, perhaps an additional source of H₂O₂. Our results suggest that H₂O₂ and ecdysone play important roles in the cryoprotective dehydration process in M. arctica, linked with the regulation of trehalose biosynthesis.
authors.affiliation: Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Novi Sad, Republic of Serbia.
authors.forename: Gordana
authors.initials: G
authors.lastname: Grubor-Lajšić
authors.forename: Edward T
authors.initials: ET
authors.lastname: Petri
authors.forename: Danijela
authors.initials: D
authors.lastname: Kojić
authors.forename: Jelena
authors.initials: J
authors.lastname: Purać
authors.forename: Zeljko D
authors.initials: ZD
authors.lastname: Popović
authors.forename: Roger M
authors.initials: RM
authors.lastname: Worland
authors.forename: Melody S
authors.initials: MS
authors.lastname: Clark
authors.forename: Miloš
authors.initials: M
authors.lastname: Mojović
authors.forename: Duško P
authors.initials: DP
authors.lastname: Blagojević
mesh_terms: D000818:Animals; D001110:Arctic Regions; D001181:Arthropods / Q000502:physiology*; D002374:Catalase / Q000378:metabolism; D003080:Cold Temperature; D003890:Desiccation; D004441:Ecdysterone / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019476:Insect Proteins / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013538:Svalbard; D014199:Trehalose / Q000378:metabolism
chemical_list: D005609:Free Radicals; D019476:Insect Proteins; D004441:Ecdysterone; D014199:Trehalose; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase