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Avoidance mechanisms of intracellular freezing and synthesis genes of ice nucleus protein

细胞内冷冻避免机制及冰核蛋白合成基因

基本信息

批准号：
11460022
负责人：
TSUMUKI Hisaaki
金额：
$ 5.38万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Low temperature tolerance or cold hardiness refers to the capacity of an organism to survive exposure to low temperatures. The tolerance is divided into two classes, freeze susceptible and freeze tolerant. Since freeze susceptible insects cannot survive ice formation in their bodies, they enhance their supercooling capacity in winter to decrease the probability of freezing. They accumulated polyols and sugars, and excrete or inactivate ice nuclei. In contract, freeze tolerant insects can survive the extracellular freezing, but not intracellular freezing. They accumulate polyols and sugars as cryoprotectants, and produce ice nuclei to avoid intracellular freezing. This research results are as follows; Diapause of Helicoverpa armigera was mainly induced by low temperatures. Diapausing pupae supercooled below -20℃ and were freezing intolerant, 2) Aphids were freezing intolerant. However, they could not survive at -10℃, even though their supercooling points were below -23℃, 3)Diapusing larvae of Chilo suppressalis were freezing tolerant. The endogenous ice nucleus production in larvae was activated by JH, which induced diapause, and was inhibited by ecdysone, which terminated diapause, 4) the ice nuclei were present on the outside of the cell membranes of the muscle and epidermis and induced the freezing of the haemolymph to prevent intracellular freezing. In cultured fat body cells of Mamestra brassicae, nonfreezing injury might be induced by the damage of Na^- and Ca^-channels rather than K^-channel, 5) In diapause-specific genes in C. suppressalis, the partial DNA clone having a length of ca 900bp was expressed only in diapausing larvae. The function of the gene has been studied, 6) Ice nucleus protein produced by Fusarium moniliforme var. subglutinans isolated from the gut of larvae of C. suppressalis was purified. Amino acids of the protein are being sequenced.

低温耐受性或抗寒性是指生物体暴露于低温下生存的能力。耐冻性分为两类：易冻性和耐冻性。由于易冻昆虫无法在体内结冰后存活，它们在冬季增强过冷能力以降低结冰的可能性。它们积累多元醇和糖，并排泄或消化细胞核。相反，耐冻昆虫可以在细胞外冷冻中存活，但不能在细胞内冷冻中存活。它们积累多元醇和糖作为冷冻保护剂，并产生冰核以避免细胞内冷冻。研究结果表明：棉铃虫滞育主要是由低温诱导的。滞育蛹在-20℃以下过冷，不耐寒;二化螟滞育幼虫的过冷却点低于-23℃，但在-10℃下不能存活。幼虫内源性冰核的产生被JH激活，诱导滞育，被蜕皮激素抑制，解除滞育。4）冰核存在于肌肉和表皮细胞膜的外侧，诱导血淋巴冻结，阻止细胞内冻结。在培养的甘蓝夜蛾脂肪体细胞中，非冷冻损伤可能是由Na^-和Ca^-通道的损伤引起的，而不是K^-通道的损伤。suppressalis中的DNA片段，其长度约为900 bp，仅在滞育幼虫中表达。对该基因的功能进行了初步研究。从C. suppressalis进行纯化。该蛋白质的氨基酸正在测序中。