注射大肠杆菌后草地贪夜蛾高龄幼虫的免疫应激反应

为采用生物技术防控草地贪夜蛾Spodoptera frugiperda的扩散为害,对草地贪夜蛾5龄和6龄幼虫注射浓度为1×109CFU/mL的大肠杆菌Escherichia coli菌液,并以注射等量磷酸盐缓冲液(phosphate buffer solution,PBS)和未做任何处理(CK)为对照,24 h后测定幼虫体重、集结数和酚氧化酶(phenoloxidase,PO)活性。结果显示,注射大肠杆菌菌液24 h后,草地贪夜蛾5龄和6龄幼虫体重均受到抑制,其体重分别为0.170 g和0.411 g,均显著低于CK的0.181 g和0.484 g;注射大肠杆菌菌液24 h后,草地贪夜蛾5龄和6龄幼虫集结数分别为135.0、338.4个索引集结数(the indexed nodules,INs),前者极显著低于后者,且均显著高于CK和PBS处理,分别为0.4、10.2个INs和0.3、10.9个INs;注射大肠杆菌菌液24 h后,草地贪夜蛾5龄幼虫PO活性为0.156 ABS·min-1·mg-1,显著高于CK和PBS处理,分别为0.046 ABS·min-1·mg-1和0.066 ABS·min-1·mg-1,但草地贪夜蛾6龄幼虫的PO活性为0.050 ABS·min-1·mg-1,显著低于CK和PBS处理,分别为0.066 ABS·min-1·mg-1和0.069 ABS·min-1·mg-1,且草地贪夜蛾5龄幼虫的PO活性显著高于6龄幼虫的PO活性。表明细菌侵染后草地贪夜蛾不同高龄幼虫的免疫应激反应存在差异,而这种差异可能受幼虫生长发育及细胞免疫和体液免疫功能之间权衡现象的影响。

Immunological and stress responses of fall armyworm Spodoptera frugiperda larvae to injecting Escherichia coli

In order to control the damage and spread of Spodoptera frugiperda by biotechnology, the immunological and stress responses of the elder-instar larvae of S. frugiperda were studied on the basis of the analysis of body mass, nodulation and phenoloxidase (PO) activity at 24 h after injecting Escherichia coli solution of 1×10⁹ CFU/mL, while the same amount of phosphate buffer solution (PBS) as control for E.coli injection. Meanwhile, those without any treatments were used as injection control (CK). The results showed that the body weight gain of both the fifth and sixth instar larvae of S. frugiperda was markedly inhibited by the E.coli injection. The body weights of the fifth and sixth instar larvae with the E.coli treatments were 0.170 g and 0.411 g, respectively, which were significantly lower than those (0.181 g and 0.484 g) of CK. For nodulation, the nodule numbers of the fifth instar larvae was 135.0 INs (the indexed nodules, INs) in the E.coli treatment, which was significantly lower than that of the sixth instar larvae (338.4 INs), and the INs of both the fifth and sixth instar larvae in respective treatments of the E.coli was significantly higher than CK values of 0.4 INs and 0.3 INs and PBS values of 10.2 INs and 10.9 INs. The PO activity of the fifth instar larvae with 0.156 ABS·min^-1·mg^-1 in the E.coli treatment was significantly higher than that of CK (0.046 ABS·min^-1·mg^-1) and PBS (0.066 ABS·min^-1·mg^-1); but it was 0.050 ABS·min^-1·mg^-1 in the sixth instar larvae that was significantly lower than that of CK (0.066 ABS·min^-1·mg^-1) and PBS (0.069 ABS·min^-1·mg^-1). In addition, the PO activity of the fifth instar larvae in the E.coli treatment was significantly higher than that of the sixth instar larvae. It is concluded that there were obvious differences in the immunological and stress responses of different instar larvae of S. frugiperda after injection by the E.coli, and the differences may be affected by the trade-offs among larval growth, cellular immunity and humoral immunity.