Transposon-mediated telomere destabilization: a driver of genome evolution in the blast fungus
Transposon-mediated telomere destabilization: a driver of genome evolution in the blast fungus
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DOI：
10.1093/nar/gkaa287
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发表时间：
2020-07-27
影响因子：
14.9
通讯作者：
Farman, Mark L.
中科院分区：
文献类型：
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作者：
Rahnama, Mostafa;Novikova, Olga;Farman, Mark L.
稻瘟病菌可导致水稻、小麦等农作物和各种牧草的毁灭性病害。来自黑麦草的菌株具有高度不稳定的染色体末端，经历了频繁的重排，这与端粒中插入的反转录转座子(稻瘟菌端粒反转录转座子)的存在有关。本研究的目的是确定运动促进端粒不稳定的机制。对亲本和新的端粒限制性片段(TRFs)进行定向克隆、作图和测序，以及基因组DNA的Minion测序，使我们能够记录109个新形成的TRFs背后的精确分子变化。这些包括亚末端rDNA序列的截断；通过“普通”端粒获得更多的插入；将Maggy反转录转座子插入到更多的阵列中；亚端粒串联重复序列的更多独立的扩展和收缩；以及通过在更多的整合过程中产生的间质端粒束的断裂而启动的各种重排。总体而言，我们估计大约60%的被分析染色体(三分之一的端粒)发生了变化。最重要的是，我们描述了一种全新的机制，通过该机制，转座子可以以极高的频率促进基因组改变，并且以一种可以促进基因组进化的方式，同时将对整个染色体结构和功能的附带损害降至最低。
The fungus Magnaporthe oryzae causes devastating diseases of crops, including rice and wheat, and in various grasses. Strains from ryegrasses have highly unstable chromosome ends that undergo frequent rearrangements, and this has been associated with the presence of retrotransposons ( Magnaporthe oryzae Telomeric Retrotransposons-MoTeRs) inserted in the telomeres. The objective of the present study was to determine the mechanisms by which MoTeRs promote telomere instability. Targeted cloning, mapping, and sequencing of parental and novel telomeric restriction fragments (TRFs), along with MinION sequencing of genomic DNA allowed us to document the precise molecular alterations underlying 109 newly-formed TRFs. These included truncations of subterminal rDNA sequences; acquisition of MoTeR insertions by 'plain' telomeres; insertion of the MAGGY retrotransposons into MoTeR arrays; MoTeR-independent expansion and contraction of subtelomeric tandem repeats; and a variety of rearrangements initiated through breaks in interstitial telomere tracts that are generated during MoTeR integration. Overall, we estimate that alterations occurred in approximately sixty percent of chromosomes (one in three telomeres) analyzed. Most importantly, we describe an entirely new mechanism by which transposons can promote genomic alterations at exceptionally high frequencies, and in a manner that can promote genome evolution while minimizing collateral damage to overall chromosome architecture and function.