拟南芥组蛋白分子伴侣AtHIRA参与体细胞同源重组及盐胁迫响应

HIRA是组蛋白H3.3的特异分子伴侣, 在组蛋白H3.3掺入染色质的过程中发挥重要作用。研究表明, HIRA在哺乳动物胚胎发育和DNA损伤修复过程中不可或缺。而目前人们对于植物中HIRA同源基因功能的研究相对较少。该研究主要关注拟南芥(Arabidopsis thaliana) AtHIRA基因在植物体细胞同源重组以及减数分裂同源重组过程中的功能。将体细胞同源重组和减数分裂同源重组报告系统分别导入野生型和hira-1突变体后统计同源重组频率, 结果表明在正常生长条件下及在伯莱霉素(bleomycin)或UV-C处理条件下, hira-1突变体体细胞的分子内和分子间同源重组频率均低于野生型。而在正常生长条件下, 野生型与hira-1突变体花粉母细胞间的减数分裂同源重组频率没有明显差异, hira-1突变体的DNA损伤水平与野生型接近。qRT-PCR结果表明, DNA损伤修复相关基因RAD51和RAD54在hira-1突变体中的表达水平均高于野生型。此外, 盐胁迫处理实验表明, hira-1突变体对于高盐胁迫更加敏感。综上, AtHIRA在拟南芥体细胞同源重组及盐胁迫响应过程中发挥了一定作用。

Histone Chaperone AtHIRA is Involved in Somatic Homologous Recombination and Salinity Response in Arabidopsis

Histone regulator (HIRA) is a specific chaperone for histone H3.3 and plays an important role in the incorporation of histone H3.3 into chromatin. HIRA is indispensable in mammalian embryo development and DNA damage repair process, but we have few studies of the function of an HIRA homolog in plants. Here, we studied the function of Arabidopsis thaliana AtHIRA in somatic homologous recombination (HR) and meiotic homologous recombination. We used the somatic HR system and the meiotic homologous recombination system in wild type and the hira-1 mutant, a loss- of-function mutant of AtHIRA. Both intramolecular and intermolecular HR frequency was lower in hira-1 than the wild type under normal growth conditions and under bleomycin or UV-C treatment, with no significant difference in the frequency of meiotic recombination of microsporocytes between the wild type and hira-1 mutant under normal growth conditions. As well, under normal growth conditions or bleomycin treatment, loss-of-function of AtHIRA in Arabidopsis did not affect the DNA damage level. On qRT-PCR, the expression of RAD51 and RAD54, two DNA repair-related genes, was higher in hira-1 than the wild type. In addition, hira-1 had a salt-sensitive phenotype as compared with the wild type under salt stress. AtHIRA may play a role in somatic HR and the salinity response in Arabidopsis.