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 res trictase treatment was observed. The frequency, types and cell-cycle d ependence of the observed abnormalities are discussed in relation to t he distinct characteristics of the enzymes and the features of the pla nt genome. The capacity to induce aberrations was not significantly in fluenced by the nature of the double-strand breaks (blunt- or cohesive -ended); however, it was dependent on the methylation status of the pl ant DNA. The restriction enzymes displayed an S-independent mode of ac tion revealing the transition between G(1) and S as the most sensitive stage of the cell cycle in barley for induction of chromosomal damage .