Hindgut Innate Immunity and Regulation of Fecal Microbiota through Melanization in Insects
Hindgut Innate Immunity and Regulation of Fecal Microbiota through Melanization in Insects
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昆虫后肠先天免疫和通过黑色化调节粪便微生物群
DOI：
10.1074/jbc.m112.354548
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发表时间：
2012-04-20
影响因子：
4.8
通讯作者：
Ling, Erjun
中科院分区：
文献类型：
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作者：
Shao, Qimiao;Yang, Bing;Ling, Erjun
许多昆虫吃植物的绿叶，但排泄黑色粪便的机制尚不清楚。昆虫无法避免与食物一起摄入病原体，这些病原体将被中肠免疫系统特异性检测到。然而，就像在哺乳动物中一样，许多病原体仍然可以逃脱昆虫的中肠免疫系统，到达后肠，在那里它们与粪便一起排出体外。本研究表明，酚氧化酶原（prophenoloxidase）诱导后肠内容物的黑色素化是粪便排泄前清除细菌的最后一道免疫防线。酚氧化酶原是一种诱导入侵者周围和伤口部位黑色素生成的关键酶。我们以家蚕为模型，发现后肠细胞产生的酚氧化酶原分泌到后肠内容物中。多次实验清楚地证明了昆虫粪便发黑是由于活化的酚氧化酶，它可以调节后肠的细菌数量。我们对家蚕后肠酚氧化酶原的分析揭示了食植物昆虫粪便呈黑色的自然秘密，并对哺乳动物后肠先天免疫的研究提供了新的见解，这在哺乳动物中尚不清楚。
Many insects eat the green leaves of plants but excrete black feces in an as yet unknown mechanism. Insects cannot avoid ingesting pathogens with food that will be specifically detected by the midgut immune system. However, just as in mammals, many pathogens can still escape the insect midgut immune system and arrive in the hindgut, where they are excreted out with the feces. Here we show that the melanization of hindgut content induced by prophenoloxidase, a key enzyme that induces the production of melanin around invaders and at wound sites, is the last line of immune defense to clear bacteria before feces excretion. We used the silkworm Bombyx mori as a model and found that prophenoloxidase produced by hindgut cells is secreted into the hindgut contents. Several experiments were done to clearly demonstrate that the blackening of the insect feces was due to activated phenoloxidase, which served to regulate the number of bacteria in the hindgut. Our analysis of the silkworm hindgut prophenoloxidase discloses the natural secret of why the phytophagous insect feces is black and provides insight into hindgut innate immunity, which is still rather unclear in mammals.