Identification of three prophenoloxidase-activating factors (PPAFs) from an invasive beetle Octodonta nipae Maulik (Coleoptera: Chrysomelidae) and their roles in the prophenoloxidase activation.
Identification of three prophenoloxidase-activating factors (PPAFs) from an invasive beetle Octodonta nipae Maulik (Coleoptera: Chrysomelidae) and their roles in the prophenoloxidase activation.
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DOI：
10.1002/arch.21425
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发表时间：
2017-10
影响因子：
2.2
通讯作者：
Huajian Zhang;B. Tang;Yaping Lin;Zhiming Chen;Xia-Fang Zhang;Tianliang Ji;Xiao-Mei Zhang;Youming Hou
中科院分区：
文献类型：
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作者：
Huajian Zhang;B. Tang;Yaping Lin;Zhiming Chen;Xia-Fang Zhang;Tianliang Ji;Xiao-Mei Zhang;Youming Hou
昆虫先天免疫系统的一个典型特征是血淋巴中丝氨酸蛋白酶级联的激活。作为原酚氧化酶（proPO）激活系统中细胞外丝氨酸蛋白酶级联的末端成分，proPO激活因子（PPAF）被上游级联激活可产生活性酚氧化酶，进而诱导下游黑化。在本研究中，我们报告了来自尼帕棕榈刚毛甲虫 Octodonta nipae (Maulik) 的 3 个 PPAF（命名为 OnPPAF1、OnPPAF2、OnPPAF3）。所有三个 OnPPAF 在氨基末端均包含一个夹结构域，随后在羧基末端包含一个胰蛋白酶样丝氨酸蛋白酶结构域，但 OnPPAF2 和 OnPPAF3 活性位点中的 Ser 被 Gly 取代。转录本表达分析显示，所有 OnPPAF 在血淋巴中均高表达，而 OnPPAF2 与 OnPPAF1 和 OnPPAF3 相比显示出极低的 mRNA 丰度，并且所有三种 OnPPAF 的丰度在细菌攻击后均显着增加。 OnPPAF1或OnPPAF3的敲低导致血淋巴酚氧化酶活性降低并抑制血淋巴黑化，而OnPPAF2的敲低不影响proPO级联。因此，我们的工作表明，三种 OnPPAF 在 O. nipae 的免疫反应过程中可能具有不同的功能和调节作用。
A typical characteristic of the insect innate immune system is the activation of the serine protease cascade in the hemolymph. As being the terminal component of the extracellular serine protease cascade in the prophenoloxidase (proPO) activating system, proPO-activating factors (PPAFs) activated by the upstream cascade may generate active phenoloxidase, which then induces downstream melanization. In the present study, we reported three PPAFs from the nipa palm hispid beetle Octodonta nipae (Maulik) (designated as OnPPAF1, OnPPAF2, OnPPAF3). All three OnPPAFs contained a single clip domain at the amino-terminus followed by a trypsin-like serine protease domain at the carboxyl-terminus, except the Ser in the active sites of OnPPAF2 and OnPPAF3 was substituted with Gly. Transcript expression analysis revealed that all OnPPAFs were highly expressed in hemolymph, whereas OnPPAF2 showed an extremely low mRNA abundance compared with that of OnPPAF1 and OnPPAF3, and that the abundance of all three OnPPAFs was dramatically increased upon bacterial challenge. Knockdown of OnPPAF1 or OnPPAF3 resulted in a reduction of hemolymph phenoloxidase activity and an inhibition of hemolymph melanization, whereas the knockdown of OnPPAF2 did not affect the proPO cascade. Our work thus implies that the three OnPPAFs may have different functions and regulation during immune responses in O. nipae.