title: Activation and epigenetic regulation of DNA transposon nDart1 in rice.
abstract: A large part of the rice genome is composed of transposons. Since active excision/reintegration of these mobile elements may result in harmful genetic changes, many transposons are maintained in a genetically or epigenetically inactivated state. However, some non-autonomous DNA transposons of the nDart1-3 subgroup, including nDart1-0, actively transpose in specific rice lines, such as pyl-v which carries an active autonomous element, aDart1-27, on chromosome 6. Although nDart1-3 subgroup elements show considerable sequence identity, they display different excision frequencies. The most active element, nDart1-0, had a low cytosine methylation status. The aDart1-27 sequence showed conservation between pyl-stb (pyl-v derivative line) and Nipponbare, which both lack autonomous activity for transposition of nDart1-3 subgroup elements. In pyl-v plants, the promoter region of the aDart1-27 transposase gene was more hypomethylated than in other rice lines. Treatment with the methylation inhibitor 5-azacytidine (5-azaC) induced transposition of nDart1-3 subgroup elements in both pyl-stb and Nipponbare plants; the new insertion sites were frequently located in genic regions. 5-AzaC treatment principally induced expression of Dart1-34 transposase rather than the other 38 aDart1-related elements in both pyl-stb and Nipponbare treatment groups. Our observations show that transposition of nDart1-3 subgroup elements in the nDart1/aDart1 tagging system is correlated with the level of DNA methylation. Our system does not cause somaclonal variation due to an absence of transformed plants, offers the possibility of large-scale screening in the field and can identify dominant mutants. We therefore propose that this tagging system provides a valuable addition to the tools available for rice functional genomics.
authors.affiliation: National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors.forename: Chang-Ho
authors.initials: CH
authors.lastname: Eun
authors.forename: Kyoko
authors.initials: K
authors.lastname: Takagi
authors.forename: Kyeung-Il
authors.initials: KI
authors.lastname: Park
authors.forename: Masahiko
authors.initials: M
authors.lastname: Maekawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Iida
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsugane
mesh_terms: D001374:Azacitidine / Q000494:pharmacology; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics*; D044127:Epigenesis, Genetic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D006877:Hydroxamic Acids / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000235:genetics*; D012639:Seeds / Q000187:drug effects / Q000235:genetics; D017422:Sequence Analysis, DNA; D019895:Transposases / Q000235:genetics / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D018744:DNA, Plant; D006877:Hydroxamic Acids; C012589:trichostatin A; D019895:Transposases; D001374:Azacitidine