XVI International Botanical Congess

The 5S rRNA gene family in Rhizidiomyces apophysatus and Hyphochytrium catenoides was investigated to determine whether 5S genes are linked or unlinked with respect to other rRNA genes, and to see whether the resulting pattern is consistent with the evolution of 5S gene organization of other stramenopilous fungi. Both organisms were found to have 5S genes linked to the rDNA repeat and to be coded on the same DNA strand as the other rRNA genes. H. catenoides also had tandem arrays of 5S sequences unlinked to the rDNA repeat. These results support the idea that the linked arrangement of 5S genes is ancestral for stramenopilous fungi but that unlinking of genes is a possibility. It was also found that the intergenic spacer (IGS) of the rDNA repeat was heterogenous, likely due to varying numbers of DNA subrepeats found in different versions of the IGS.