Izumi Yohei, Sonoda Shoji, Yoshida Hideya, Danks Hugh V, Tsumuki Hisaaki
Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan.
J Insect Physiol. 2006 Feb;52(2):215-20. doi: 10.1016/j.jinsphys.2005.11.001. Epub 2005 Dec 15.
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.
水稻二化螟（Chilo suppressalis）的越冬幼虫会积累甘油，并且能够耐受约-25摄氏度的低温。然而，非滞育幼虫无法积累甘油，会被冻死。我们比较了在选定的冷冻温度下，这些幼虫脂肪体组织中的组织损伤程度、甘油浓度的影响以及甘油和水的转运情况。当在-20摄氏度下用0.25 M甘油冷冻时，越冬幼虫的组织能够存活，而非滞育幼虫的组织则不能，但甘油提供的保护作用会被水通道抑制剂氯化汞抵消。较高浓度（0.75 M）的甘油甚至能为非滞育幼虫的脂肪体提供一定保护。对越冬幼虫的放射性示踪分析表明，冷冻过程中水分从组织中流出，而甘油进入组织，并且氯化汞会破坏这一过程。在-35摄氏度的致死性冷冻后，转运也会受到干扰。因此，水和甘油的膜转运参与了水稻二化螟脂肪体细胞避免冷冻损伤的过程，显然是通过介导耐冻组织中甘油取代水来实现的。
