title: Evolution of rDNA ITS1 and ITS2 sequences and RNA secondary structures within members of the fungal genera Grosmannia and Leptographium.
abstract: The two internal transcribed spacers (ITS) of the nuclear ribosomal (r) DNA tandem repeat were examined in ophiostomatoid fungi belonging to the genera Grosmannia and Leptographium and closely-related taxa. Although the DNA sequence of the ITS region evolves rapidly, core features of the RNA secondary structure of the ITS1 and ITS2 segments are conserved. The results demonstrate that structural conservation of GC-rich helical regions is facilitated primarily through compensatory base changes (CBCs), hemi-CBCs, and compensating insertions/deletions (indels), although slippage of the RNA strand is potentially an additional mechanism for maintaining basepairing interactions. The major conclusion of the structural analysis of both ITS segments is that two factors appear to be involved in limiting the type of changes observed: a high GC bias for both ITS1 and ITS2 and structural constraints at the RNA level.
authors: Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
authors: Taylor
authors: T
authors: Mullineux
authors: Georg
authors: G
authors: Hausner
mesh_terms: D000818:Animals; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics*; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics*; D019143:Evolution, Molecular; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D055155:Ophiostomatales / Q000235:genetics*; D010802:Phylogeny; D012331:RNA, Fungal / Q000737:chemistry; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012331:RNA, Fungal