Holliday Junction Resolvase MOC1 Maintains Plastid and Mitochondrial Genome Integrity in Algae and Bryophytes
Holliday Junction Resolvase MOC1 Maintains Plastid and Mitochondrial Genome Integrity in Algae and Bryophytes
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DOI：
10.1104/pp.20.00763
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发表时间：
2020-12-01
期刊：
影响因子：
7.4
通讯作者：
Miyagishima, Shin-ya
中科院分区：
文献类型：
--
作者：
Kobayashi, Yusuke;Odahara, Masaki;Miyagishima, Shin-ya
在一些藻类和植物中，单核叶绿体1通过阻止短的分散重复序列之间的异位重组来监视质体和线粒体DNA的重组。当DNA双链断裂发生时，在同源重组过程中形成称为霍利迪连接（HJ）的四链DNA结构。由于HJ通过共价键连接同源DNA，因此HJ的解析对于终止同源重组和忠实地分离DNA分子对至关重要。我们最近在藻类和植物中鉴定出单核叶绿体1（Monokaryotic Chloroplast1，MOC1）是一种质体DNA HJ解离酶。虽然十字形切割核酸内切酶1（CCE1）在酵母中被鉴定为线粒体DNA HJ解离酶，但在其他真核生物中尚未鉴定出同源物或其他线粒体HJ解离酶。在这里，我们证明了MOC1耗尽在绿色衣藻莱茵衣藻和苔藓小立碗藓诱导ptDNA中的短分散重复序列之间的异位重组。此外，MOC1耗竭破坏质体中的类囊体膜。在一些陆地植物谱系中，如苔藓P.patens，苔类和蕨类植物，MOC1双重靶向质体和线粒体。此外，MOC1的线粒体靶向也预测轮藻和一些陆地植物物种。MOC1缺失除了引起质体DNA的不稳定性外，还引起线粒体DNA中短分散重复序列介导的异位重组和线粒体嵴的紊乱。先前分别在质体靶向（RECA2）和线粒体靶向（RECA1）重组酶的突变体中观察到质体和线粒体中的相似表型。这些结果表明，MOC1在双链断裂修复中起作用，其中重组酶产生HJ，MOC1在藻类和植物的某些谱系的线粒体以及藻类和植物的质体中解析HJ。
Monokaryotic Chloroplast1 acts in recombination surveillance of plastid and mitochondrial DNA in some algae and plants by preventing ectopic recombination between short dispersed repeats. When DNA double-strand breaks occur, four-stranded DNA structures called Holliday junctions (HJs) form during homologous recombination. Because HJs connect homologous DNA by a covalent link, resolution of HJ is crucial to terminate homologous recombination and segregate the pair of DNA molecules faithfully. We recently identified Monokaryotic Chloroplast1 (MOC1) as a plastid DNA HJ resolvase in algae and plants. Although Cruciform cutting endonuclease1 (CCE1) was identified as a mitochondrial DNA HJ resolvase in yeasts, homologs or other mitochondrial HJ resolvases have not been identified in other eukaryotes. Here, we demonstrate that MOC1 depletion in the green alga Chlamydomonas reinhardtii and the moss Physcomitrella patens induced ectopic recombination between short dispersed repeats in ptDNA. In addition, MOC1 depletion disorganized thylakoid membranes in plastids. In some land plant lineages, such as the moss P. patens, a liverwort and a fern, MOC1 dually targeted to plastids and mitochondria. Moreover, mitochondrial targeting of MOC1 was also predicted in charophyte algae and some land plant species. Besides causing instability of plastid DNA, MOC1 depletion in P. patens induced short dispersed repeat-mediated ectopic recombination in mitochondrial DNA and disorganized cristae in mitochondria. Similar phenotypes in plastids and mitochondria were previously observed in mutants of plastid-targeted (RECA2) and mitochondrion-targeted (RECA1) recombinases, respectively. These results suggest that MOC1 functions in the double-strand break repair in which a recombinase generates HJs and MOC1 resolves HJs in mitochondria of some lineages of algae and plants as well as in plastids in algae and plants.