Cuckoo Fungus Mimics Termite Eggs by Producing the Cellulose-Digesting Enzyme β-Glucosidase
Cuckoo Fungus Mimics Termite Eggs by Producing the Cellulose-Digesting Enzyme β-Glucosidase
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DOI：
10.1016/j.cub.2008.11.030
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发表时间：
2009-01-13
期刊：
影响因子：
9.2
通讯作者：
Tamura, Takashi
中科院分区：
文献类型：
--
作者：
Matsuura, Kenji;Yashiro, Toshihisa;Tamura, Takashi
昆虫和真菌在不同的栖息地有着悠久的联系历史，包括木材分解生态位[7]。白蚁卵的真菌模仿是昆虫-真菌结合最显著的进化结果之一[2,3]。网白蚁属的白蚁通常会将真菌菌核（称为“白蚁球”）和卵一起藏在育室中，这样真菌就能在白蚁巢中获得一个没有竞争对手的栖息地。这种真菌需要复杂的形态和化学伪装来模仿白蚁卵b[3]。然而，真菌化学模仿卵子的机制尚不清楚。在这里，我们表明真菌通过产生纤维素消化酶-葡萄糖苷酶在化学上模仿白蚁卵。我们发现白蚁卵识别信息素由-葡萄糖苷酶和溶菌酶组成。这两种酶都是白蚁唾液中的主要化合物，也在白蚁卵中产生。只有当真菌产生β -葡萄糖苷酶时，白蚁才会照料白蚁球。我们的研究结果表明，白蚁和真菌之间的纤维素消化生态位重叠，共享相同的化学物质，为真菌模仿白蚁卵的起源提供了机会。这表明信息素化合物最初可能是在其他生命史背景下进化的，只是后来在化学通讯中获得了功能。
Insects and fungi share a long history of association in various habitats, including the wood-decomposition niche [7]. Fungal mimicry of termite eggs is one of the most striking evolutionary consequences of insect-fungus association [2, 3]. Termites of the genus Reticulitermes often harbor fungal sclerotia, called "termite balls," along with eggs in nursery chambers, whereby the fungus gains a competitor-free habitat in termite nests. Sophisticated morphological and chemical camouflage are needed for the fungus to mimic termite eggs [3]. However, the mechanism of chemical egg mimicry by the fungus is unknown. Here, we show that the fungus mimics termite eggs chemically by producing the cellulose-digesting enzyme beta-glucosidase. We found that the termite egg-recognition pheromone consists of beta-glucosidase and lysozyme. Both enzymes are major salivary compounds in termites and are also produced in termite eggs. Termite balls were tended by termites only when the fungus produced beta-glucosidase. Our results demonstrated that the overlap of the cellulose digestion niche between termites and the fungus sharing the same chemicals provided the opportunity for the origin of termite egg mimicry by the fungus. This suggests that pheromone compounds might have originally evolved within other life history contexts, only later gaining function in chemical communication.