State Key Laboratory of Genetic Engineering and Institute of Genetics, Institute of Plant Biology, Center for Evolutionary Biology, School of Life Sciences, Fudan University, Shanghai, 200433, China.
Department of Biology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA.
New Phytol. 2014 Jan;201(1):292-304. doi: 10.1111/nph.12498. Epub 2013 Sep 18.
The eukaryotic RAD51 gene family has seven ancient paralogs conserved between plants and animals. Among these, RAD51, DMC1, RAD51C and XRCC3 are important for homologous recombination and/or DNA repair, whereas single mutants in RAD51B, RAD51D or XRCC2 show normal meiosis, and the lineages they represent diverged from each other evolutionarily later than the other four paralogs, suggesting possible functional redundancy. The function of Arabidopsis RAD51B, RAD51D and XRCC2 genes in mitotic DNA repair and meiosis was analyzed using molecular genetic, cytological and transcriptomic approaches. The relevant double and triple mutants displayed normal vegetative and reproductive growth. However, the triple mutant showed greater sensitivity than single or double mutants to DNA damage by bleomycin. RNA-Seq transcriptome analysis supported the idea that the triple mutant showed DNA damage similar to that caused by bleomycin. On bleomycin treatment, many genes were altered in the wild-type but not in the triple mutant, suggesting that the RAD51 paralogs have roles in the regulation of gene transcription, providing an explanation for the hypersensitive phenotype of the triple mutant to bleomycin. Our results provide strong evidence that Arabidopsis XRCC2, RAD51B and RAD51D have complex functions in somatic DNA repair and gene regulation, arguing for further studies of these ancient genes that have been maintained in both plants and animals during their long evolutionary history.
真核生物 RAD51 基因家族在植物和动物之间有七个古老的同源基因。其中 RAD51、DMC1、RAD51C 和 XRCC3 对同源重组和/或 DNA 修复很重要，而 RAD51B、RAD51D 或 XRCC2 的单突变体表现出正常的减数分裂，它们所代表的谱系在进化上比其他四个同源基因分化得更晚，这表明可能存在功能冗余。利用分子遗传学、细胞学和转录组学方法分析了拟南芥 RAD51B、RAD51D 和 XRCC2 基因在有丝分裂 DNA 修复和减数分裂中的功能。相关的双突变体和三突变体显示出正常的营养生长和生殖生长。然而，三突变体对博来霉素引起的 DNA 损伤比单突变体或双突变体更敏感。RNA-Seq 转录组分析支持三突变体表现出与博来霉素相似的 DNA 损伤的观点。在博来霉素处理下，许多基因在野生型中发生了改变，但在三突变体中没有改变，这表明 RAD51 同源基因在基因转录调控中具有作用，为三突变体对博来霉素的超敏表型提供了一个解释。我们的研究结果为拟南芥 XRCC2、RAD51B 和 RAD51D 在体细胞 DNA 修复和基因调控中具有复杂功能提供了有力证据，这表明需要进一步研究这些在植物和动物漫长进化历史中都被保留下来的古老基因。
