Agriculture Victoria, AgriBio, Centre for AgriBioscience, 5 Ring Road, La Trobe University, Bundoora, Victoria, 3083, Australia.
Dairy Futures Cooperative Research Centre, Bundoora, Australia.
Sci Rep. 2017 Aug 22;7(1):9024. doi: 10.1038/s41598-017-07886-2.
Molecular characterisation has convincingly demonstrated some types of horizontal gene transfer in eukaryotes, but nuclear gene transfer between distantly related eukaryotic groups appears to have been rare. For angiosperms (flowering plants), nuclear gene transfer events identified to date have been confined to genes originating from prokaryotes or other plant species. In this report, evidence for ancient horizontal transfer of a fungal nuclear gene, encoding a ß-1,6-glucanase enzyme for fungal cell wall degradation, into an angiosperm lineage is presented for the first time. The gene was identified from de novo sequencing and assembly of the genome and transcriptome of perennial ryegrass, a cool-season grass species. Molecular analysis confirmed the presence of the complete gene in the genome of perennial ryegrass. No corresponding sequence was found in other plant species, apart from members of the Poeae sub-tribes Loliinae and Dactylidinae. Evidence suggests that a common ancestor of the two sub-tribes acquired the gene from a species ancestral to contemporary grass-associated fungal endophytes around 9-13 million years ago. This first report of horizontal transfer of a nuclear gene from a taxonomically distant eukaryote to modern flowering plants provides evidence for a novel adaptation mechanism in angiosperms.
分子特征已经令人信服地证明了真核生物中存在某些类型的水平基因转移，但远缘真核生物群之间的核基因转移似乎很少发生。对于被子植物（开花植物），迄今为止鉴定的核基因转移事件仅限于源自原核生物或其他植物物种的基因。在本报告中，首次提出了真菌核基因（编码真菌细胞壁降解的β-1,6-葡聚糖酶的酶）从真菌到被子植物谱系的古老水平转移的证据。该基因是从多年生黑麦草的基因组和转录组从头测序和组装中鉴定出来的，多年生黑麦草是一种冷季草种。分子分析证实该基因存在于多年生黑麦草的基因组中。除了 Poeae 亚族 Loliinae 和 Dactylidinae 的成员外，在其他植物物种中未发现相应的序列。有证据表明，这两个亚族的共同祖先在大约 900 到 1300 万年前从当代与草相关的真菌内生菌的祖先中获得了该基因。这是首例从分类学上遥远的真核生物到现代开花植物的核基因水平转移的报告，为被子植物的一种新的适应机制提供了证据。
