Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.
PLoS One. 2011 Jan 27;6(1):e16548. doi: 10.1371/journal.pone.0016548.
Saccharomycotina and Taphrinomycotina lack intron in their histone genes, except for an intron in one of histone H4 genes of Yarrowia lipolytica. On the other hand, Basidiomycota and Perizomycotina have introns in their histone genes. We compared the distributions of 81, 47, 79, and 98 introns in the fungal histone H2A, H2B, H3, and H4 genes, respectively. Based on the multiple alignments of the amino acid sequences of histones, we identified 19, 13, 31, and 22 intron insertion sites in the histone H2A, H2B, H3, and H4 genes, respectively. Surprisingly only one hot spot of introns in the histone H2A gene is shared between Basidiomycota and Perizomycotina, suggesting that most of introns of Basidiomycota and Perizomycotina were acquired independently. Our findings suggest that the common ancestor of Ascomycota and Basidiomycota maybe had a few introns in the histone genes. In the course of fungal evolution, Saccharomycotina and Taphrinomycotina lost the histone introns; Basidiomycota and Perizomycotina acquired other introns independently. In addition, most of the introns have sequence similarity among introns of phylogenetically close species, strongly suggesting that horizontal intron transfer events between phylogenetically distant species have not occurred recently in the fungal histone genes.
子囊菌门和外囊菌门的组蛋白基因中没有内含子，除了假丝酵母的一个组蛋白 H4 基因中有内含子。另一方面，担子菌门和后鞭毛生物门的组蛋白基因中有内含子。我们比较了真菌组蛋白 H2A、H2B、H3 和 H4 基因中分别有 81、47、79 和 98 个内含子的分布。基于组蛋白氨基酸序列的多重比对，我们在组蛋白 H2A、H2B、H3 和 H4 基因中分别鉴定出 19、13、31 和 22 个内含子插入位点。令人惊讶的是，在组蛋白 H2A 基因中只有一个内含子热点在担子菌门和后鞭毛生物门之间共享，这表明大多数担子菌门和后鞭毛生物门的内含子是独立获得的。我们的研究结果表明，子囊菌门和担子菌门的共同祖先的组蛋白基因中可能有几个内含子。在真菌进化过程中，子囊菌门和外囊菌门失去了组蛋白内含子；担子菌门和后鞭毛生物门独立获得了其他内含子。此外，大多数内含子在亲缘关系较近的物种的内含子之间具有序列相似性，强烈表明在真菌组蛋白基因中，亲缘关系较远的物种之间的水平内含子转移事件最近并未发生。
