TY - JOUR
T1 - Effects of diapause and cold-acclimation on the avoidance of freezing injury in fat body tissue of the rice stem borer, Chilo suppressalis Walker
AU - Izumi, Yohei
AU - Sonoda, Shoji
AU - Tsumuki, Hisaaki
N1 - Funding Information:
We thank Dr. Hugh V. Danks, Canadian Museum of Nature, for his valuable comments and critical reading of the manuscript. This study was supported in part by Grant-in-Aid for Scientific Research (B) (16380042) and (shourei) (18922002) from the Japan Society for the Promotion of Science and a grant from the Ohara Foundation for Agricultural Research.
PY - 2007/7
Y1 - 2007/7
N2 - Overwintering freeze-tolerant larvae of Chilo suppressalis can survive at -25 °C, but non-diapausing larvae cannot. We reported earlier that to prevent intracellular freezing, which causes death in overwintering larvae of the Saigoku ecotype distributed in southwestern Japan, water leaves and glycerol enters fat body cells through water channels during freezing. However, it is still unclear how diapause and low-temperature exposure are related to the acquisition of freeze tolerance. We compared the extent of tissue damage, accumulation of glycerol, and transport of glycerol and water in fat body tissues between cold-acclimated and non-acclimated non-diapausing and diapausing larvae. The tissue from cold-acclimated diapausing larvae could survive only when frozen in Grace's insect medium with 0.25 M glycerol at -20 °C. The protection provided by glycerol was offset by mercuric chloride, which is a water-channel inhibitor. Fat body tissue isolated from non-acclimated diapausing larvae was injured by freezing even though glycerol was added to the medium, but the level of freezing injury was significantly lower than in non-diapausing larvae. Radiotracer assays in cold-acclimated diapausing larvae showed that during freezing, water left the cells into the medium and glycerol entered the cells from the medium at the same time. Therefore, in Saigoku ecotype larvae of the rice stem borer, both diapause and cold-acclimation are essential to accumulate glycerol and activate aquaporin for the avoidance of freezing injury.
AB - Overwintering freeze-tolerant larvae of Chilo suppressalis can survive at -25 °C, but non-diapausing larvae cannot. We reported earlier that to prevent intracellular freezing, which causes death in overwintering larvae of the Saigoku ecotype distributed in southwestern Japan, water leaves and glycerol enters fat body cells through water channels during freezing. However, it is still unclear how diapause and low-temperature exposure are related to the acquisition of freeze tolerance. We compared the extent of tissue damage, accumulation of glycerol, and transport of glycerol and water in fat body tissues between cold-acclimated and non-acclimated non-diapausing and diapausing larvae. The tissue from cold-acclimated diapausing larvae could survive only when frozen in Grace's insect medium with 0.25 M glycerol at -20 °C. The protection provided by glycerol was offset by mercuric chloride, which is a water-channel inhibitor. Fat body tissue isolated from non-acclimated diapausing larvae was injured by freezing even though glycerol was added to the medium, but the level of freezing injury was significantly lower than in non-diapausing larvae. Radiotracer assays in cold-acclimated diapausing larvae showed that during freezing, water left the cells into the medium and glycerol entered the cells from the medium at the same time. Therefore, in Saigoku ecotype larvae of the rice stem borer, both diapause and cold-acclimation are essential to accumulate glycerol and activate aquaporin for the avoidance of freezing injury.
KW - Chilo suppressalis
KW - Cold-acclimation
KW - Diapause
KW - Freeze tolerance
KW - Glycerol
KW - Water
UR - http://www.scopus.com/inward/record.url?scp=34447518767&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34447518767&partnerID=8YFLogxK
U2 - 10.1016/j.jinsphys.2007.04.005
DO - 10.1016/j.jinsphys.2007.04.005
M3 - Article
C2 - 17543330
AN - SCOPUS:34447518767
VL - 53
SP - 685
EP - 690
JO - Journal of Insect Physiology
JF - Journal of Insect Physiology
SN - 0022-1910
IS - 7
ER -