Ancient origin of glycosyl hydrolase family 9 cellulase genes
Ancient origin of glycosyl hydrolase family 9 cellulase genes
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DOI：
10.1093/molbev/msi107
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发表时间：
2005-05-01
影响因子：
10.7
通讯作者：
Blaxter, M
中科院分区：
文献类型：
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作者：
Davison, A;Blaxter, M
虽然人们普遍认为大多数动物（后生动物）不具有内源性纤维素酶，而是依赖于肠道共生体进行纤维素消化，但在白蚁、鲍鱼和海葵的基因组中发现的糖基水解酶家族9（GHF 9）纤维素酶可能是个例外。使用表达的序列标签的信息，我们表明，GHF9基因（亚组E2）是广泛分布在后生动物，因为至少有11个类在5门表达GHF9纤维素酶。我们还表明，真核细胞GHF9基因家族是古老的，在植物和动物中形成不同的单系群。由于几个内含子的位置也是保守的四个后生动物门，然后，相反的仍然普遍认为，纤维素酶水平转移到动物相对较近，GHF9基因必须来自一个古老的祖先。我们还发现，从同一动物门分离的序列往往在一起组，在一些后口类，GHF9基因的特点是在催化重要位点的取代。GHF9的几个旁系同源亚科可以在植物中鉴定，并且来自原始物种的基因倾向于出现在被子植物代表的基部。相比之下，GHF9亚组E2基因在细菌中相对罕见。
While it is widely accepted that most animals (Metazoa) do not have endogenous cellulases, relying instead on intestinal symbionts for cellulose digestion, the glycosyl hydrolase family 9 (GHF9) cellulases found in the genomes of termites, abalone, and sea squirts could be an exception. Using information from expressed sequence tags, we show that GHF9 genes (subgroup E2) are widespread in Metazoa because at least 11 classes in five phyla have expressed GHF9 cellulases. We also demonstrate that eukaryotic GHF9 gene families are ancient, forming distinct monophyletic groups in plants and animals. As several intron positions are also conserved between four metazoan phyla then, contrary to the still widespread belief that cellulases were horizontally transferred to animals relatively recently, GHF9 genes must derive from an ancient ancestor. We also found that sequences isolated from the same animal phylum tend to group together, and in some deuterostomes, GHF9 genes are characterized by substitutions in catalytically important sites. Several paralogous subfamilies of GHF9 can be identified in plants, and genes from primitive species tend to arise basally to angiosperm representatives. In contrast, GHF9 subgroup E2 genes are relatively rare in bacteria.