Maeda Taro, Kobayashi Yuuki, Kameoka Hiromu, Okuma Nao, Takeda Naoya, Yamaguchi Katsushi, Bino Takahiro, Shigenobu Shuji, Kawaguchi Masayoshi
Division of Symbiotic Systems, National Institute for Basic Biology, Myodaiji Nishigonaka, Okazaki, Aichi, 444-8585, Japan.
The Graduate University for Advanced Studies [SOKENDAI], Hayama, Miura, Kanagawa, 240-0193, Japan.
Commun Biol. 2018 Jul 10;1:87. doi: 10.1038/s42003-018-0094-7. eCollection 2018.
Arbuscular mycorrhizal fungus (AMF) species are some of the most widespread symbionts of land plants. Our much improved reference genome assembly of a model AMF, DAOM-181602 (total contigs = 210), facilitated a discovery of repetitive elements with unusual characteristics. has only ten or 11 copies of complete 45S rDNAs, whereas the general eukaryotic genome has tens to thousands of rDNA copies. rDNAs are highly heterogeneous and lack a tandem repeat structure. These findings provide evidence for the hypothesis that rDNA heterogeneity depends on the lack of tandem repeat structures. RNA-Seq analysis confirmed that all rDNA variants are actively transcribed. Observed rDNA/rRNA polymorphisms may modulate translation by using different ribosomes depending on biotic and abiotic interactions. The non-tandem repeat structure and intragenomic heterogeneity of AMF rDNA/rRNA may facilitate successful adaptation to various environmental conditions, increasing host compatibility of these symbiotic fungi.
丛枝菌根真菌（AMF）物种是陆地植物中分布最广泛的共生体之一。我们对模式AMF DAOM-181602进行了大幅改进的参考基因组组装（总重叠群=210），这有助于发现具有异常特征的重复元件。它只有10或11个完整的45S rDNA拷贝，而一般真核生物基因组有数十到数千个rDNA拷贝。rDNA高度异质，缺乏串联重复结构。这些发现为rDNA异质性取决于缺乏串联重复结构这一假说提供了证据。RNA测序分析证实所有rDNA变体都在活跃转录。观察到的rDNA/rRNA多态性可能通过根据生物和非生物相互作用使用不同核糖体来调节翻译。AMF rDNA/rRNA的非串联重复结构和基因组内异质性可能有助于成功适应各种环境条件，增加这些共生真菌与宿主的兼容性。
