INTERGENIC SPACERS OF RIBOSOMAL-RNA GENES IN 3 SPECIES OF THE CYNAREAE (ASTERACEAE)

Intergenic spacers of the rRNA genes of three species of the Cynareae tribe: Cynara cardunculus subsp. scolymus (artichoke), Onopordum acant hium, and O. illyricum were cloned in the plasmid pGEM-7zf(+). Detaile d restriction mapping and partial sequencing of the IGSs were carried out. The structural analysis showed a clear diversity between Cynara a nd Onopordum, while a high degree of homology was found between the tw o Onopordum spp. In all three species a fragment of about 450 bp from the 5' end of 18S to the Acc I site with a high sequence homology was present. Nucleotide sequences upstream from the above mentioned Acc I site show a gradual decrease of homology between Cynara and Onopordum.