Evidence for the presence of a cellulase gene in the last common ancestor of bilaterian animals
Evidence for the presence of a cellulase gene in the last common ancestor of bilaterian animals
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DOI：
10.1098/rsbl.2003.0016
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发表时间：
2003-08-07
影响因子：
4.7
通讯作者：
Sugimura, M
中科院分区：
文献类型：
--
作者：
Lo, N;Watanabe, H;Sugimura, M
直到最近，教科书上关于动物纤维素水解的观点是肠道共生生物如细菌或单细胞真核生物负责产生纤维素酶。这一观点受到了一些无脊椎动物内源性纤维素酶基因的表征和测序的挑战，包括植物寄生线虫，节肢动物和软体动物。这些基因中的大多数在序列上完全不相关，它们的进化起源仍然不清楚。在植物寄生线虫的情况下，已经提出，它们的祖先通过水平基因转移从原核生物获得了纤维素酶基因，并且最近在海鞘中发现的纤维素酶基因也提出了类似的建议。为了加深对动物纤维素酶进化的了解，我们在GenBank中搜索了所有已知类型的这些酶，并进行了系统发育比较。低系统发育分辨率被发现在大多数的序列检查，然而，位置的同一性，在纤维素酶基因的内含子从白蚁，海鞘和鲍鱼提供了令人信服的证据表明，一个类似的基因存在于最后的共同祖先的原口动物和后口动物。在一个不同的酶家族中，发现甲虫和植物寄生线虫的纤维素酶聚集在一起。这一结果质疑横向基因转移到后者的祖先的想法，尽管统计测试不允许排除这种可能性。总体而言，我们的研究结果表明，至少有一个家庭的内源性纤维素酶可能比以前认为的更广泛的动物。
Until recently, the textbook view of cellulose hydrolysis in animals was that gut-resident symbiotic organisms such as bacteria or unicellular eukaryotes are responsible for the cellulases produced. This view has been challenged by the characterization and sequencing of endogenous cellulase genes from some invertebrate animals, including plant-parasitic nematodes, arthropods and a mollusc. Most of these genes are completely unrelated in terms of sequence, and their evolutionary origins remain unclear. In the case of plant-parasitic nematodes, it has been suggested that their ancestor obtained a cellulase gene via horizontal gene transfer from a prokaryote, and similar suggestions have been made about a cellulase gene recently discovered in a sea squirt. To improve understanding about the evolution of animal cellulases, we searched for all known types of these enzymes in GenBank, and performed phylogenetic comparisons. Low phylogenetic resolution was found among most of the sequences examined, however, positional identity in the introns of cellulase genes from a termite, a sea squirt and an abalone provided compelling evidence that a similar gene was present in the last common ancestor of protostomes and deuterostomes. In a different enzyme family, cellulases from beetles and plant-parasitic nematodes were found to cluster together. This result questions the idea of lateral gene transfer into the ancestors of the latter, although statistical tests did not allow this possibility to be ruled out. Overall, our results suggest that at least one family of endogenous cellulases may be more widespread in animals than previously thought.