Mutation in the catalytic subunit of DNA polymerase α influences transcriptional gene silencing and homologous recombination in Arabidopsis

• Published in: The Plant journal : for cell and molecular biology Vol. 61; no. 1; pp. 36 - 45
• Main Authors: Liu, Jun, Ren, Xiaozhi, Yin, Haibo, Wang, Yu, Xia, Ran, Wang, Youqun, Gong, Zhizhong
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 2010; Blackwell Publishing Ltd; Blackwell
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis Proteins - physiology; Biological and medical sciences; Blotting, Northern; Blotting, Southern; Blotting, Western; Catalytic Domain - genetics; Catalytic Domain - physiology; Cell Cycle - genetics; Cell Cycle - physiology; Chromatin Immunoprecipitation; DNA Methylation; DNA polymerase alpha; DNA Polymerase I - genetics; DNA Polymerase I - metabolism; DNA Polymerase I - physiology; DNA-directed DNA polymerase; epigenetic; epigenetics; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - genetics; Gene Expression Regulation, Plant - physiology; homologous recombination; Mutation; Nuclear Proteins - genetics; Plant physiology and development; Plants, Genetically Modified - genetics; Plants, Genetically Modified - growth & development; Plants, Genetically Modified - metabolism; Promoter Regions, Genetic - genetics; Recombination, Genetic - genetics; Reverse Transcriptase Polymerase Chain Reaction; Catalytic subunit; Enzyme; Arabidopsis; epigenetic; Transferases; Homologous recombination; DNA polymerase alpha; Arabidopsis thaliana; Gene silencing; Nucleotidyltransferases; Cruciferae; Dicotyledones; DNA; Angiospermae; Epigenetics; DNA methylation; Spermatophyta; Mutation; Methylation; DNA-directed DNA polymerase
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2009.04026.x

REPRESSOR OF SILENCING 1 (ROS1) encodes a DNA demethylase that actively removes DNA methylation. Mutation in ROS1 leads to transcriptional gene silencing of a T-DNA locus that contains two genes, RD29A-LUC and 35S-NPTII, originally expressed in the C24 wild type. These units have different silencing regulation mechanisms: the former mechanism is dependent on small interfering RNA (siRNA)-directed DNA methylation, but the latter is not. We studied the latter gene silencing mechanism by screening the suppressors of the ros1 mutant using the silenced 35S-NPTII as a selection marker gene. The polα/incurvata2 (icu2) gene was isolated as one ros1 suppressor because its mutation leads to the reactivation of the silenced 35S-NPTII gene. POLα/ICU2 encodes a catalytic subunit of DNA polymerase α. Mutation of POLα/ICU2 did not affect DNA methylation, but reduced histone H3 Lys9 dimethylation (H3K9me2) modification in the 35S promoter. The polα mutation also influences the development of the shoot apical meristem, and delays the G2/M phase with high expression of a G2/M marker gene CycB1;1:GUS. Furthermore, the frequency of homologous recombination is greater in the polα/icu2 mutant than in the C24 wild type. Our results suggest that DNA polymerase α is involved in mediating epigenetic states and in DNA homologous recombination in Arabidopsis.