title: Role of membrane transport of water and glycerol in the freeze tolerance of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae).
abstract: Overwintering larvae of the rice stem borer, Chilo suppressalis accumulate glycerol and are freezing tolerant to about -25 degrees C. However, non-diapausing larvae cannot accumulate glycerol and are killed by freezing. We compared the extent of tissue damage, the effects of glycerol concentration, and the transport of glycerol and water in fat body tissues from these larvae at selected freezing temperatures. Tissues from overwintering larvae, but not non-diapausing larvae, survive when frozen at -20 degrees C with 0.25 M glycerol, but the protection afforded by glycerol is offset by the water-channel inhibitor mercuric chloride. Glycerol in higher concentration (0.75 M) affords some protection even to the fat body of non-diapausing larvae. Radiotracer assays of overwintering larvae show that water leaves the tissues during freezing while glycerol enters, and that mercuric chloride disrupts this process. Transport is also disrupted after lethal freezing at -35 degrees C. Therefore, membrane transport of water and glycerol is involved in the avoidance of freezing injury to fat body cells of the rice stem borer, apparently by mediating the replacement of water with glycerol in freezing-tolerant tissues.
authors.affiliation: Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Izumi
authors.forename: Shoji
authors.initials: S
authors.lastname: Sonoda
authors.forename: Hideya
authors.initials: H
authors.lastname: Yoshida
authors.forename: Hugh V
authors.initials: HV
authors.lastname: Danks
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Tsumuki
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000502:physiology; D003080:Cold Temperature; D005216:Fat Body / Q000502:physiology; D005615:Freezing; D005990:Glycerol / Q000378:metabolism*; D007915:Lepidoptera / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D008627:Mercuric Chloride / Q000494:pharmacology; D014867:Water / Q000378:metabolism / Q000502:physiology*
chemical_list: D020346:Aquaporins; D026901:Membrane Transport Proteins; D014867:Water; D008627:Mercuric Chloride; D005990:Glycerol