Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenee to defend against bacterial infection
Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenee to defend against bacterial infection
复制标题
亚洲玉米螟防御细菌感染需要剪辑域酚氧化酶激活蛋白酶
DOI：
10.1016/j.dci.2018.06.014
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发表时间：
2018-10-01
影响因子：
2.9
通讯作者：
Tang, Tai
中科院分区：
文献类型：
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作者：
Feng, Congjing;Zhao, Ya;Tang, Tai
昆虫中的酚氧化酶原(PPO)激活系统在抵御微生物入侵中起着重要作用。在本论文中，我们从亚洲玉米螟中鉴定了一个PPO激活蛋白(命名为OfPAP)，它含有一个1203bp的开放阅读框，编码一个由两个CLIP结构域和一个C末端丝氨酸蛋白酶结构域组成的400个残基的蛋白。SignalP分析显示了一个由18个残基组成的信号肽。OfPAP的成熟残基长度为382个残基，计算的M-r为44.8 kDa，等电点为6.66。多序列比对和系统发育分析表明，OfPAP与其他鳞翅目昆虫的PAPs同源。注射灭活枯草芽孢杆菌后4h，幼虫血细胞中的转录水平显著升高，而体壁中的转录水平从4~12hPI持续升高，24HPI开始下降。OfPAP表达沉默后，感染大肠杆菌的幼虫的半数致死时间(LT50)(1.0d)显著低于野生型(3.0d，p<；0.01)。与未注射dsRNA的对照幼虫相比，OfPAP基因敲除幼虫血淋巴中的E.coil克隆形成单位增加了3.5倍。OfPAP基因敲除幼虫血淋巴中PO和IEARase活性显著降低。综上所述，我们已经证明了OfPAP是PPO激活系统的一个组成部分，可能是通过在亚洲玉米象幼虫中作为PPO激活蛋白酶发挥作用。
The prophenoloxidase (PPO) activating system in insects plays an important role in defense against microbial invasion. In this paper, we identified a PPO activating protease (designated OfPAP) containing a 1203 bp open reading frame encoding a 400-residue protein composed of two clip domains and a C-terminal serine protease domain from Ostrinia furnacalis. SignalP analysis revealed a putative signal peptide of 18 residues. The mature OfPAP was predicted to be 382 residues long with a calculated M-r of 44.8 kDa and pI of 6.66. Multiple sequence alignment and phylogenetic analysis indicated that OfPAP was orthologous to the PAPs in the other lepidopterans. A large increase of the transcript levels was observed in hemocytes at 4 h post injection (hpi) of killed Bacillus subtilis, whereas its level in integument increased continuously from 4 to 12 hpi in the challenged larvae and began to decline at 24 hpi. After OfPAP expression had been silenced, the median lethal time (LT50) of Escherichia coli-infected larvae (1.0 day) became significantly lower than that of E. con-infected wild-type (3.0 days, p < 0.01). A 3.5-fold increase in E. coil colony forming units occurred in larval hemolymph of the OfPAP knockdown larvae, as compared with that of the control larvae not injected with dsRNA. There were notable decreases in PO and IEARase activities in hemolymph of the OfPAP knockdown larvae. In summary, we have demonstrated that OfPAP is a component of the PPO activation system, likely by functioning as a PPO activating protease in O. furnacalis larvae.