Restriction endonucleases induce chromosomal aberrations in barley

The clastogenic ability of the restriction endonucleases (MspI, HpaII and HaeIII) in germinating seeds of reconstructed barley karyotype was assessed. An effective induction of chromosomal aberrations after restrictase treatment was observed. The frequency, types and cell-cycle dependence of the observed abnormalities are discussed in relation to the distinct characteristics of the enzymes and the features of the plant genome. The capacity to induce aberrations was not significantly influenced by the nature of the double-strand breaks (blunt- or cohesive-ended) ; however, it was dependent on the methylation status of the plant DNA. The restriction enzymes displayed an S-independent mode of action revealing the transition between G 1 and S as the most sensitive stage of the cell cycle in barley for induction of chromosomal damage.