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侵染期的拟双角斯氏线虫Steinernema ceratophorumD43品系体外都包裹着一个透明的体鞘。为探明体鞘对线虫侵染力的影响,了解鞘蛋白(sheath proteins,SPs)对大蜡螟Galleria mellonella幼虫的免疫抑制作用,本研究通过化学方法使拟双角斯氏线虫D43脱鞘,以对寄主的致死率和侵入点数量为指标,与包鞘线虫比较对大蜡螟幼虫的侵染力;采用乙醇提取的方法获得线虫鞘蛋白,利用双向电泳和质谱技术对鞘蛋白进行鉴定分析;从血细胞数量和酚氧化酶活力两个方面评价鞘蛋白对大蜡螟幼虫免疫反应的抑制作用。结果表明:0.5%次氯酸钠处理20min可以保证95%以上的线虫存活和脱鞘。与包鞘线虫相比,脱鞘线虫对大蜡螟幼虫的致死率显著降低,致死时间延后,节间膜侵入点数量显著减少。以35%乙醇提取的鞘蛋白提取物可鉴定出6种鞘蛋白,其中一个被鉴定为丝氨酸蛋白酶。此外,血腔注射鞘蛋白提取物可导致试虫血细胞数量明显降低,酚氧化酶活力受到显著抑制。由此说明,体鞘对拟双角斯氏线虫D43的侵染力具有显著影响,鞘蛋白在抑制寄主昆虫免疫反应中发挥重要作用。
The infecting stage of the Steinernema ceratophorum D43 strain is enveloped by a transparent sheath. In order to find out the effect of sheath on nematode infectivity, we know the immunosuppressive effects of sheath proteins (SPs) on Galleria mellonella larvae. In this study, D43 was dehisced by chemical method, The infectivity of larvae of larvae was compared with that of C. heltophthalmus on the lethal rate of host and the number of invasion points. Nematode sheath protein was obtained by ethanol extraction, and the sheath protein was identified by two-dimensional electrophoresis and mass spectrometry The inhibitory effect of sheath protein on the immune response of S. larvae was evaluated from the number of blood cells and the activity of phenoloxidase. The results showed that: 0.5% sodium hypochlorite treatment 20min can ensure that more than 95% of nematodes survival and dehairing. Compared with the sheath-sheath nematodes, the mortality of D. exigua larvae was significantly reduced, the lethal time delayed, and the number of invagination points of internodes significantly decreased. Six sheath proteins were identified from the sheath protein extract extracted with 35% ethanol, one of which was identified as serine protease. In addition, intratumoral injection of sheath protein extract can lead to a significant decrease in the number of hemolymph cells, phenoloxidase activity was significantly inhibited. Thus, the body sheath had a significant effect on the infectivity of D43, and the sheath protein played an important role in inhibiting the immune response of host insects.