IN-SITU MOLECULAR-GENETIC CHARACTERIZATION OF REPETITIVE DNA - A DIFFERENT EXPERIMENTAL APPROACH

It would be of great interest to be able to characterize the DNA, part icularly repetitive DNA, directly in situ, without separating it from its natural position inside the cell: in fact, this type of experiment al approach could allow a better understanding of the effective relati onship existing between form and function and could contribute to clar ify some problems of plant biology not easily approached with other te chniques. For this purpose, the use of restriction enzymes in situ is becoming particularly useful. In the present paper the authors propose a <<molecular/genetic>> characterization of the interphasic nuclei of Aegilops speltoides resulting from a combination of this method with other histochemical techniques, followed by an elaboration of the resu lting data by means of computer image analysis. Specifically, interpha sic nuclei, previously characterized by DAPI, were submitted to <<C-Ba nding>> treatment, followed by Giemsa staining. Parallelely, other nuc lei were digested, in situ, with the restriction enzymes EcoRi, Alu I and HAE III and than stained with Feulgen technique. The obtained dat a were then elaborated by image analysis. The results show the presenc e, in the interphase nuclei of this plant, of a dense mass of species- specific heterochromatin which covers on average 37.5% of the entire n uclear surface; this mass contains a fraction of highly repetitive DNA rich in A + T that represents on average 22.1% of the total nuclear s urface. The technical approach proposed in the present paper could be very useful for a characterization of repetitive DNA directly on the i nterphasic nuclei of plants.