ORGANIZATION OF A SOLANUM BREVIDENS REPETITIVE SEQUENCE RELATED TO THE TGRI SUBTELOMERIC REPEATS OF LYCOPERSICON-ESCULENTUM

A species-specific repetitive DNA fragment has been isolated from a ge nomic library of Solanum brevidens. Sequence analysis revealed a regul ar organization of three non-homologous subrepeats forming tandemly-ar ranged composite repetitive units. Interpretation of Southern hybridiz ation patterns based on the known sequence data suggests that the isol ated sequence element represents an abundant organization type, althou gh the presence of simple tandem arrays of the subrepeats is also indi cated. Seventy-four percent sequence similarity was found between one of the S. brevidens subrepeats (Sb4AX) and a satellite DNA (TGRI) loca lized as a subtelomeric repeat on almost all Lycopersicon esculentum c hromosomes. Insitu hybridization indicated that, similarly to TGRI, th e S. brevidens-specific repeats are located at the ends of the arms of several chromosomes. On the basis of the data obtained, a common ance stral sequence can be proposed for the tomato (TGRI) and the S. brevid ens (Sb4AX) repeat however, the molecular organization of this element in these two species evolved in a basically different manner.