ROR1/RPA2A, a Putative Replication Protein A2, Functions in Epigenetic Gene Silencing and in Regulation of Meristem Development inArabidopsis

Abstract

We screened for suppressors of repressor of silencing1 (ros1) using the silenced 35S promoter-neomycin phosphotransferase II (Pro 35S :NPTII) gene as a marker and identified two allelic mutants, ror1-1 and ror1-2 (for suppressor of ros1). Mapbased cloning revealed that ROR1 encodes a 31-kD protein similar to DNA replication protein A2 (RPA2A). Mutations in ROR1 reactivate the silenced Pro 35S :NPTII gene but not RD29A promoter-luciferase in the ros1 mutant. DNA methylation in rDNA, centromeric DNA, and RD29A promoter regions is not affected by ror1. However, chromatin immunoprecipitation data suggest that histone H3 acetylation is increased and histone H3K9 dimethylation is decreased in the 35S promoter in the ror1 ros1 mutant compared with ros1. These results indicate that release of silenced Pro 35S :NPTII by ror1 mutations is independent of DNA methylation. ROR1/RPA2A is strongly expressed in shoot and root meristems. Mutations in ROR1/ RPA2A affect cell division in meristems but not final cell sizes. Our work suggests important roles of ROR1/RPA2A in epigenetic gene silencing and in the regulation of plant development.

The second subunit of DNA-polymerase delta is required for genomic stability and epigenetic regulation

“…However, pold2-1 had little effect on the ProRD29A:LUC locus in dms3-4. Like mutants of DNA replication-related proteins (Elmayan et al, 2005;Xia et al, 2006;Yin et al, 2009;Liu et al, 2010aLiu et al, , 2010b, pold2-1 failed to suppress the silenced ProRD29A:LUC in the ros1-1 mutant (Fig. 1F).…”

“…1C). TSIs are endogenous TGS loci (Steimer et al, 2000), the expression of which is altered in some mutants involved in DNA methylation, histone modification, or DNA replication (Steimer et al, 2000;Xia et al, 2006;Yin et al, 2009;Liu et al, 2010aLiu et al, , 2010b. The expression of TSIs was increased in these isolated mutants (Fig.…”

“…In Arabidopsis (Arabidopsis thaliana), mutations in replication factor C1 (RFC1), Pol «, Pol a, and replication protein A2A (RPA2A) can suppress gene silencing in a DNA methylation-independent manner (Elmayan et al, 2005;Kapoor et al, 2005;Xia et al, 2006;Liu et al, 2010aLiu et al, , 2010b. These mutants are hypersensitive to DNA damage and exhibit reduced telomere length and increased genomic instability.…”

Replication Protein A (RPA1a) Is Required for Meiotic and Somatic DNA Repair But Is Dispensable for DNA Replication and Homologous Recombination in Rice

“…AtRPA1a is required for interference-sensitive crossover formation but dispensable for meiotic DSB repair (Osman et al, 2009), and the atrpa1b (At5g08020) mutant is indistinguishable from wild type under normal conditions but is hypersensitive to MMS and UV-B (Ishibashi et al, 2005). In addition, mutant plants with one of the AtRPA2 subunits (At2g24490) are smaller than wild type and the transcriptional gene silencing is suppressed in a DNAmethylation-independent manner (Elmayan et al, 2005;Kapoor et al, 2005;Xia et al, 2006), indicating that these individual RPA subunits have different functions in Arabidopsis DNA metabolism.…”

Regulating DNA Replication in Plants

“…Moreover, studies with mutant plants revealed that Arabidopsis RPA1A and RPA1C (nuclear proteins) are essential for DNA replication, whereas RPA1B (chloroplast and nuclear) is not essential and is required only during DNA repair (Sakaguchi et al 2009). Apart from its function in DNA replication, RPA2 is also required to maintain transcriptional silencing of a subset of transposon elements (Elmayan et al 2005;Kapoor et al 2005;Xia et al 2006). …”