Open AccessAn extrachromosomal form of the Mu transposons of maize.
Author(s) -
Venkatesan Sundaresan,
Michael Freeling
Publication year - 1987
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.84.14.4924
Subject(s) - extrachromosomal dna , transposable element , transposition (logic) , biology , dna , base pair , microbiology and biotechnology , genetics , retrotransposon , plasmid , mutant , gene , linguistics , philosophy
Maize lines known as Robertson's Mutator (Mu) lines generate unstable recessive mutations at high frequencies. These lines carry actively transposing copies of the transposons (Tn) Mu1 and Mu1.7. TnMu1 and TnMu1.7 are approximately 1400 and 1700 base pairs long, respectively, and they have 210-base-pair terminal inverted repeats. We report here extrachromosomal forms of TnMu1 and TnMu1.7. The extrachromosomal Mu1 and Mu1.7 molecules are resistant to alkaline denaturation and to proteinase treatment and have circular restriction maps; therefore, they are probably covalently closed circular DNA. Further, we show that their occurrence is correlated with Mu activity, so they are probably generated during Mu transposition as transposition intermediates or as products of Mu excision. When the total extrachromosomal supercoiled DNA from immature male flowers of a Mu line was examined by electron microscopy, the Mu transposons appeared to constitute a significant fraction of the extrachromosomal DNA circles in Mu lines.