Isolation of a single-stranded extrachromosomal DNA from germinating wheat embryos.

Newly-synthesized cytoplasmic non-mitochondrial DNA was isolated from wheat embryos which had been germinated in the presence of [14C]-thymidine for a time period not long enough to trigger the first post-dormant round of the nuclear DNA replication. This extrachromosomal DNA fraction consisted of linear single-stranded polydeoxyribonucleotide chains, corresponding in size to approximately 1.1 X 10(6) daltons, and amounted to about 0.5% of the total cellular DNA content. It is suggested that the appearance of the newly-synthesized polydeoxyribonucleotide chains in the cytoplasm may be a physiological signal for the initiation of the nuclear DNA replication in germinating wheat embryo cells.