ORGANIZATION AND DISTRIBUTION OF A SAU3A TANDEM REPEATED DNA-SEQUENCEIN PICEA (PINACEAE) SPECIES

Repeated DNA families contribute to the large genomes of coniferous tr ees but are poorly characterized. We report the analysis of a 142 bp t andem repeated DNA sequence identified by the restriction enzyme Sau3A and found in approximately 20 000 copies in Picea glauca. Southern hy bridization indicated that the repented DNA family is specific to the genus, was amplified early in its evolution, and has undergone little structural alteration over evolutionary time. Fluorescence in situ hyb ridization localized arrays of the Sau3A repeating element to the cent romeric regions of different subsets of the metaphase chromosomes of P . glauca and the closely related Picea sitchensis, suggesting that mec hanisms leading to the intragenomic movement of arrays may be more act ive than those lending to mutation of the repenting elements themselve s. Unambiguous identification of P. glauca and P. sitchensis chromosom es was made possible by co-localizing the Sau3A tandem repeats and the genes encoding the 5S and 18S-5.8S-26S ribosomal RNAs.