Huang Xiaodan, Jing Dapeng, Prabu Sivaprasath, Zhang Tiantao, Wang Zhenying
Engineering Research Center of Natural Enemy Insects, Institute of Biological Control, Jilin Agricultural University, Changchun 130118, China.
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Insects. 2022 Nov 10;13(11):1041. doi: 10.3390/insects13111041.
Phenoloxidase (PO) is an important enzyme in the cellular immune system and is involved in defense against a wide range of pathogens, including . Vip3Aa19 is secreted and expressed by (Bt) at the middle exponential growth phase and is a kind of protein with efficient insecticidal activity against . However, immune responses of the target insects have been regarded as a hindrance to Bt pathogenicity. This paper reports two phenoloxidase (PO) genes (PAE and PO2) identified from the hemocyte transcriptome data of the fall armyworm, qRT-PCR validation results showed that the expression levels of two PO genes were significantly upregulated after Vip3Aa19 (LC = 4.98 µg/g) toxin treatment compared with those of fed an insecticide-free artificial diet. Meanwhile, two PO genes were expressed from the egg to adult stages even without an immune challenge. We noticed that at all developmental stages investigated in the , PAE was generally expressed at a higher level than PO2. However, after Vip3Aa19 treatment, the PO2 gene mRNA expression level was significantly elevated in response to the toxin challenge. An injection of a specific double-stranded RNA (dsRNA) against POs could suppress its expression. The third instar larvae of treated with dsRNA were much more susceptible to Vip3Aa19 toxin than the control larvae were. Notably, the mortality rate was nearly 90% after a dsPO2 injection. These results proved that PO2 was more important for the survival of . Finally, RNA interference and then PO activity detection revealed that PO genes mainly existed in the hemolymph and played an important role in immune defense against Bt toxin.
酚氧化酶（PO）是细胞免疫系统中的一种重要酶，参与抵御多种病原体，包括……Vip3Aa19由苏云金芽孢杆菌（Bt）在指数生长中期分泌并表达，是一种对……具有高效杀虫活性的蛋白质。然而，目标昆虫的免疫反应被认为是Bt致病性的一个障碍。本文报道了从草地贪夜蛾血细胞转录组数据中鉴定出的两个酚氧化酶（PO）基因（PAE和PO2），qRT-PCR验证结果表明，与饲喂不含杀虫剂的人工饲料的草地贪夜蛾相比，Vip3Aa19（LC = 4.98 µg/g）毒素处理后两个PO基因的表达水平显著上调。同时，即使没有免疫刺激，两个PO基因从卵期到成虫期都有表达。我们注意到，在草地贪夜蛾所研究的所有发育阶段，PAE的表达水平通常高于PO2。然而，Vip3Aa19处理后，PO2基因的mRNA表达水平因毒素刺激而显著升高。注射针对POs的特异性双链RNA（dsRNA）可以抑制其表达。用dsRNA处理的草地贪夜蛾三龄幼虫比对照幼虫对Vip3Aa19毒素更敏感。值得注意的是，注射dsPO2后死亡率接近90%。这些结果证明PO2对草地贪夜蛾的存活更为重要。最后，RNA干扰然后检测PO活性表明，PO基因主要存在于血淋巴中，在抵御Bt毒素的免疫防御中起重要作用。
