异色瓢虫胁迫对棉铃虫生长发育及压力蛋白基因表达的影响

【目的】明确不同食源异色瓢虫(Harmonia axyridis)胁迫对棉铃虫(Helicoverpa armigera)生长发育和变态发育的影响,探讨棉铃虫是否能感知并分级捕食风险、能否在生长发育和变态发育上体现出权衡效应;明确长时和短时胁迫对棉铃虫压力蛋白基因表达的影响,探讨异色瓢虫胁迫能否引起棉铃虫分子水平上的生理反应。【方法】通过设置7种不同食源的异色瓢虫胁迫处理(饥饿处理、虾卵处理、棉铃虫幼虫处理、棉铃虫卵处理、蚜虫处理、蚜虫对照处理、对照处理),观察记录棉铃虫在胁迫下的生长发育(幼虫历期、蛹历期、雌雄蛾寿命、总寿命)和变态发育(蛹重、化蛹率、羽化失败率、卷翅率)指标;设置长时(1龄幼虫至3日龄成虫)和短时(15 min至6 h)异色瓢虫胁迫处理,利用实时荧光定量PCR(q RT-PCR)技术检测棉铃虫压力蛋白基因(即热激蛋白基因)Hsp70和Hsp90及热激同源蛋白基因Hsc70在胁迫后的表达水平变化。【结果】在捕食性天敌异色瓢虫的胁迫下,棉铃虫幼虫历期、蛹期、雌雄蛾寿命、总寿命均显著性缩短,蛹重和化蛹率显著性下降,成虫卷翅率显著性升高,而羽化失败率无显著性变化。在不同食源的天敌胁迫下,棉铃虫幼虫历期在异色瓢虫取食蚜虫时最短,蛹历期在瓢虫取食棉铃虫卵时最短,总寿命在瓢虫取食虾卵时最短,而雌雄蛾寿命在不同食源天敌胁迫下未表现出显著性差异;棉铃虫成虫卷翅率在瓢虫取食棉铃虫卵时最高,而蛹重、化蛹率、羽化失败率在不同食源天敌胁迫下未表现出显著性差异。压力蛋白基因Hsp70和Hsp90在短时胁迫下(Hsp70:30min至3 h;Hsp90:15 min、1.5 h、2 h、6 h)表达水平显著性上调,热激同源蛋白基因Hsc70在长时胁迫下(5龄幼虫、预蛹、雄蛹、雌蛾阶段)表达水平显著性上调。【结论】在面对捕食性天敌异色瓢虫长时胁迫作用下,棉铃虫各生长发育阶段均出现缩短的现象,即棉铃虫为躲避被捕食风险表现出了发育加速的现象,而快速的生长发育在一定程度上干扰了变态发育,导致蛹重和化蛹率下降,成虫卷翅率提高,符合权衡效应。棉铃虫对不同食源的天敌胁迫具有不同程度的敏感性,即棉铃虫对潜在的捕食风险可能存在一定的分级能力,但这种分级能力没有得到规律性体现。异色瓢虫胁迫能够引起棉铃虫分子层面的生理反应,导致压力蛋白基因的表达上调,其中压力蛋白基因Hsp70和Hsp90受到短时胁迫的反应较为明显,而热激同源蛋白基因Hsc70受到慢性胁迫刺激的反应更为显著。

Effects of Predator-Induced Stress from Harmonia axyridis on the Development and Stress Protein Gene Expression of Helicoverpa armigera

【Objective】 The objective of this study is to determine the effects of predator-induced stress from Harmonia axyridis with various feeding resources on the development and metamorphose of Helicoverpa armigera, illustrating that whether He. armigera can perceive and classify the predation risk, and show the trade-off characteristic between the development and metamorphose, and to determine the effects of long-term and short-term stress on the stress protein gene expression of He. armigera, illustrating that whether the predator-induced stress from Ha. axyridis can induce the physiological reactions of He. armigera at molecular level. 【Method】The development (larval and pupal duration, female and male longevity, and total longevity) and metamorphose (pupae weight, pupation rate, fail eclosion rate, and wrinkled-wing rate) indicators of He. armigera were observed and recorded under the predator-induced stress from Ha. axyridis with 7 kinds of feeding resources (hungry treatment, shrimp egg treatment, cotton bollworm larva treatment, cotton bollworm egg treatment, aphid treatment, CK treatment with aphid, and CK treatment). Long-term (first instar larvae to 3-day-old moth) and short-term (15 min to 6 h) stress treatments were set up, and the changes of stress protein genes (heat shock protein genes) Hsp70 and Hsp90, heat shock cognate protein gene Hsc70 expression were determined under the predator-induced stress by quantitative real-time PCR (qRT-PCR). 【Result】Under the predator-induced stress from Ha. axyridis, larval and pupal duration, female and male longevity, and total longevity of He. armigera shortened, pupal weight and pupation rate decreased, and wrinkled-wing rate increased significantly, whereas the fail eclosion rate was not influenced by the predator-induced stress. Under the predator-induced stress from Ha. axyridis with various food sources, the larval duration of He. armigera was the shortest when predators consumed aphids, the pupal duration was the shortest when predators consumed cotton bollworm eggs, and the total longevity was the shortest when predators consumed shrimp eggs, whereas the female and male longevity were not influenced by the diets of Ha. axyridis. The wrinkled-wing rate of He. armigera was the highest when predators consumed cotton bollworm eggs, whereas the pupal weight, pupation rate, and fail eclosion rate were not influenced by the diets of Ha. axyridis. Stress protein genes Hsp70 and Hsp90 were up-regulated after short-term stress (Hsp70: 30 min to 3 h; Hsp90: 15 min, 1.5 h, 2 h and 6 h), whereas heat shock cognate protein gene Hsc70 was up-regulated after long-term stress (the stages of 5th instar larvae, prepupa, male pupae and male moth). 【Conclusion】Under the long-term stress from Ha. axyridis, all developmental stages of He. armigera shortened, and the development of He. armigera became faster to avoid the predation risk. The developmental acceleration might disturb the metamorphose of He. armigera to some degree, leading the smaller pupal weight, lower pupation rate, and higher wrinkled-wing rate, which was according with the trade-off hypothesis. The sensitiveness of He. armigera to predator-induced stress were different among various diets of Ha. axyridis, and He. armigera might be able to classify the potential predation risk, however this ability showed a degree of uncertainty. The predator-induced stress from Ha. axyridis could induce the physiological reactions of He. armigera at molecular level, leading the higher expression levels of stress protein genes. Hsp70 and Hsp90 expressions were more affected by the short-term stress, whereas Hsc70 expression was more affected by long-term stress.