Yin Haibo, Zhang Xia, Liu Jun, Wang Youqun, He Junna, Yang Tao, Hong Xuhui, Yang Qing, Gong Zhizhong
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Plant Cell. 2009 Feb;21(2):386-402. doi: 10.1105/tpc.108.061549. Epub 2009 Feb 24.
Based on abscisic acid (ABA) inhibition of seed germination and seedling growth assays, we isolated an ABA overly sensitive mutant (abo4-1) caused by a mutation in the Arabidopsis thaliana POL2a/TILTED1(TIL1) gene encoding a catalytic subunit of DNA polymerase epsilon. The dominant, ABA-insensitive abi1-1 or abi2-1 mutations suppressed the ABA hypersensitivity of the abo4-1 mutant. The abo4/til1 mutation reactivated the expression of the silenced Athila retrotransposon transcriptional silent information (TSI) and the silenced 35S-NPTII in the ros1 mutant and increased the frequency of somatic homologous recombination (HR) approximately 60-fold. ABA upregulated the expression of TSI and increased HR in both the wild type and abo4-1. MEIOTIC RECOMBINATION11 and GAMMA RESPONSE1, both of which are required for HR and double-strand DNA break repair, are expressed at higher levels in abo4-1 and are enhanced by ABA, while KU70 was suppressed by ABA. abo4-1 mutant plants are sensitive to UV-B and methyl methanesulfonate and show constitutive expression of the G2/M-specific cyclin CycB1;1 in meristems. The abo4-1 plants were early flowering with lower expression of FLOWER LOCUS C and higher expression of FLOWER LOCUS T and changed histone modifications in the two loci. Our results suggest that ABO4/POL2a/TIL1 is involved in maintaining epigenetic states, HR, and ABA signaling in Arabidopsis.
基于脱落酸（ABA）对种子萌发和幼苗生长的抑制试验，我们分离出了一个ABA超敏突变体（abo4-1），它是由拟南芥POL2a/TILTED1（TIL1）基因突变引起的，该基因编码DNA聚合酶ε的催化亚基。显性的、ABA不敏感的abi1-1或abi2-1突变抑制了abo4-1突变体的ABA超敏性。abo4/til1突变重新激活了ros1突变体中沉默的Athila反转录转座子转录沉默信息（TSI）和沉默的35S-NPTII的表达，并使体细胞同源重组（HR）频率增加了约60倍。ABA上调了TSI的表达，并在野生型和abo4-1中均增加了HR。MEIOTIC RECOMBINATION11和GAMMA RESPONSE1是HR和双链DNA断裂修复所必需的，它们在abo4-1中表达水平更高，并被ABA增强，而KU70则被ABA抑制。abo4-1突变体植株对UV-B和甲磺酸甲酯敏感，并在分生组织中组成型表达G2/M特异性细胞周期蛋白CycB1;1。abo4-1植株开花早，FLOWER LOCUS C表达较低，FLOWER LOCUS T表达较高，且这两个位点的组蛋白修饰发生了变化。我们的结果表明，ABO4/POL2a/TIL1参与维持拟南芥中的表观遗传状态、HR和ABA信号传导。
