THE 5S-RNA GENES IN PINUS-RADIATA AND THE SPACER REGION AS A PROBE FOR RELATIONSHIPS BETWEEN PINUS SPECIES

The 5S RNA genes in Pinus radiata occur in two size classes of about 850 and 525 bp in length. Representatives from both the long and short size classes were cloned and sequenced. The primary difference in the two size classes was shown to be a 330 bp insertion in the spacer region of the long units. Within an individual breeding clone of P. radiata there was some sequence heterogeneity between representatives of the short class. The 5S RNA genes in thirty pine species were characterised using either a clone of the short size class or a subclone of the 330 bp insertion characterizing the long size class. Eleven species of subg. Strobus were examined and all lacked the long type of unit of radiata pine. The New World species of subg. Pinus all had both short and long units whereas the Old World species had long units. The implications of these results for the evolution of the 5S DNA sequences and the phylogenetic relationships within Pinus are discussed.