Together yes, but not coupled: new insights into the roles of RAD51 and DMC1 in plant meiotic recombination.
Together yes, but not coupled: new insights into the roles of RAD51 and DMC1 in plant meiotic recombination.
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DOI：
10.1111/j.1365-313x.2011.04845.x
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发表时间：
2012-03
期刊：
影响因子：
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通讯作者：
M. Pradillo;E. López;R. Linacero;C. Romero;N. Cuñado;E. Sanchez-Moran;J. Santos
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文献类型：
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作者：
M. Pradillo;E. López;R. Linacero;C. Romero;N. Cuñado;E. Sanchez-Moran;J. Santos
真核重组酶 RAD51 和 DMC1 对于减数分裂期间同源染色体之间的 DNA 链交换至关重要。 RAD51 也在有丝分裂过程中表达，并介导姐妹染色单体之间的同源重组 (HR)。有人认为DMC1可能参与体细胞中从姐妹间染色单体重组到同源减数分裂重组的转变。在减数分裂时，拟南芥 Atrad51 无效突变体无法突触并出现广泛的染色体断裂。 Atdmc1 无效突变体也是无突触的，但在这种情况下不存在染色体碎片。因此，在植物中，AtDMC1似乎对于同源间同源重组是不可或缺的，而AtRAD51似乎更多地参与姐妹间重组。在这项工作中，我们研究了一种新的AtRAD51敲低突变体Atrad51-2，它仅表达少量的RAD51蛋白。 Atrad51-2 突变体植物不育并且对 DNA 双链断裂诱导高度敏感，但它们的营养发育显然是正常的。突变体的减数分裂表型包括部分突触、单价染色体频率升高、染色体断裂发生率低和多价染色体关联。令人惊讶的是，51% 的二价体涉及非同源染色体。 Atrad51-2 背景中 AtDMC1 的缺失会导致二价体的丢失和染色体碎片的增加。我们的结果表明，需要达到临界水平的 AtRAD51 才能确保染色体间交换过程中 HR 的保真度。假设在重组的初始步骤中存在不对称 DNA 链入侵，我们开发了一个工作模型，其中链入侵的初始步骤由 AtDMC1 介导，需要 AtRAD51 来检查该过程的保真度。
The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologous chromosomes during meiosis. RAD51 is also expressed during mitosis, and mediates homologous recombination (HR) between sister chromatids. It has been suggested that DMC1 might be involved in the switch from intersister chromatid recombination in somatic cells to interhomolog meiotic recombination. At meiosis, the Arabidopsis Atrad51 null mutant fails to synapse and has extensive chromosome fragmentation. The Atdmc1 null mutant is also asynaptic, but in this case chromosome fragmentation is absent. Thus in plants, AtDMC1 appears to be indispensable for interhomolog homologous recombination, whereas AtRAD51 seems to be more involved in intersister recombination. In this work, we have studied a new AtRAD51 knock-down mutant, Atrad51-2, which expresses only a small quantity of RAD51 protein. Atrad51-2 mutant plants are sterile and hypersensitive to DNA double-strand break induction, but their vegetative development is apparently normal. The meiotic phenotype of the mutant consists of partial synapsis, an elevated frequency of univalents, a low incidence of chromosome fragmentation and multivalent chromosome associations. Surprisingly, non-homologous chromosomes are involved in 51% of bivalents. The depletion of AtDMC1 in the Atrad51-2 background results in the loss of bivalents and in an increase of chromosome fragmentation. Our results suggest that a critical level of AtRAD51 is required to ensure the fidelity of HR during interchromosomal exchanges. Assuming the existence of asymmetrical DNA strand invasion during the initial steps of recombination, we have developed a working model in which the initial step of strand invasion is mediated by AtDMC1, with AtRAD51 required to check the fidelity of this process.