健康与遗传心理学研究室知识库

飞蝗(Locusta m.zgratoria L.)是一种重要的农业害虫，广泛分布于东半球，它们对极端温度的适应能力是决定其分布及种群动态的重要因素之一。尤其在全球气候变暖的背景下，探讨飞蝗对极端温度的适应性及其生理、遗传机制更有重要的理论和实践意义。我们已经了解，飞蝗地理种群之间、季节之间和发育阶段之间，其抗寒性都有明显变异，而且具有冷驯化能力和快速冷驯化现象，也研究了飞蝗蝗卵温度耐性的遗传特征以及生理机制。本研究我们将进一步探讨群居型与散居型飞蝗蝗卵耐寒性的差异，以及造成这种差异的生理机制，同时探讨热激蛋白在抗寒过程中和种群高密度压力下所起的作用。主要结果如下:

昆虫种群的高密度对他们自身来说是一种压力，热激蛋白可以应对于压力而表达。群居型一与散居型飞蝗飞别是飞蝗种群在高密度与低密度下存在的虫态，我们希望通过实验比较六种热激蛋白在两型飞蝗不同发育阶段的表达情况，来揭示热激蛋白在飞蝗应对不同种群密度下的作用。hsp20.瓦20.反20. 7, 4叹70和hsp90的全长cDNA被克隆，实时定量PCR的结果说明这六种热激蛋白除了在飞蝗蝗卵的早期阶段不能被检测到外，在中、后期蝗卵和1—5龄的蝗蛹中都有表达，表达水平在群居型飞蝗中普遍高于散居型飞蝗。并且这六种热激蛋白的表达在群居型飞蝗5龄蝗蛹的头、胸、后腿的表达量都高于散居型飞蝗。结果显示，高种群密度作为一种压力影响到飞蝗中热激蛋白的表达。

群居型飞蝗与散居型飞蝗蝗卵的抗寒能力有明显的差异，散居型飞蝗蝗卵的抗寒性显著的高于群居型。群居型飞蝗蝗卵的鲜重和干重都显著的高于散居型蝗卵，但是在发育中期两型蝗卵的过冷却点之间无显著性差异。在不同的低温驯化时间下，两型蝗卵的抗寒力均显著升高，但散居型蝗卵的抗寒力仍然高于群居型。在经受不同温度(0、-5、-10 0C)和不同时间(1, 2, 4小时)的低温胁迫后，六种热激蛋白在群居型蝗卵中的表达量均显著的高于散居型。在两型蝗卵中，六种热激蛋白的表达均是在常温恢复2小时左右达到高峰。

两型蝗卵在低温下的差异基因表达谱表现出不同的趋势。群居型蝗卵的基因表达谱只在一些与耐寒性增强无明显关系的通路中占有优势，包括表皮蛋白发

The migratory locust Locusta migratoria L., which is distributed widely in the eastern hemisphere, has long been regarded as an important agricultural pest. Their adaptable capacity to extreme temperature is the most important factor that influences their distribution and population abundance. Under global warming scenarios especially, determining adaptation to extreme temperature, heritability and physiological mechanism of thermotolerance of the migratory locust has an important bearing on general theories and implication. Now, we have known that there are geographical, seasonal and developmental variations in the cold hardiness of the migratory locust, and the migratory locust has cold acclimation and rapid cold hardening capacity. The research on heredity characters and physiological mechanisms of thermotolerance of locust eggs has been done. In this study we will determine the differences in cold hardness between the eggs of gregarious locusts and solitary locusts, the influence on cold hardness of locust eggs by cooling rate and thermoperiodic acclimation, and explore the roles of heat shock proteins (lisps) in adaptation to coldness and high density stress. The main results are as follows.

The high population density of insects is often a stress factor to themselves, which synthesize Hsps in response to the stress impacts through molecular chaperone activity. The locust solitary and gregarious phases occur at low and high population density, respectively. We attempt to interpret the roles of Hsps in adaptation to high density population, by comparing the expression profiles of the hsps in the two phases of the locust. The full length cDNA of hsp20.5, 20. 6, 20. 7, 40, 70 and hsp90 of the migratory locust was cloned and sequenced. The expressional differentiation of six hsps in mRNA levels between solitary and gregarious locusts was tested. The results from the real-time PCR indicate that six Hsps are expressed throughout developmental stages except in the early-stage embryo. The expression levels of six hsps are significantly up-regulated in gregarious locusts. The expressional variation from specific organs, head, thorax and leg of St" instar nymphs appears that gregarious locusts are also higher than those in solitary ones. The results indicate that the density as a kind of stressed factor affects the expression of hsp genes in the locust.

There are obvious differences in cold hardness between the eggs of gregarious locusts and solitary locusts, the latter significantly higher than the former. The wet weight and dry weight of gregarious locust eggs are significantly higher than solitary locust eggs, but no solid divergence is observed in the supercooling point between them in the middle development stage. Their cold hardness is promoted remarkably after various cold acclimations, nevertheless solitary locust eggs are still stronger than gregarious ones in cold hardness. Six Hsps (hsp20.5, 20.6, 20. 7, 40, 70 and hsp90) are expressed with a higher level in gregarious locust eggs than in solitary ones after treated under various low temperatures (0，-5，-10°C ) during various periods (1，2, 4 hours). Their expression peaks all appear around 2 hours after the two types of eggs are put back to the normal temperature.