Sk. Hwang et Jg. Kim, SMALL-SUBUNIT RIBOSOMAL DNA OF AN ECTOMYCORRHIZAL FUNGUS TRICHOLOMA MATSUTAKE - SEQUENCE, STRUCTURE, AND PHYLOGENETIC ANALYSIS, Molecules and Cells, 8(3), 1998, pp. 251-258
A 2861 bp nucleotide sequence containing Tricholoma Introduction matsu
take SSU rRNA gene and its flanking regions was determined and analyze
d. Comparison with known SSU rDNA sequences and primer extension analy
sis revealed that the SSU rRNA coding region and intergenic spacer 2 (
IGS2) are 1805 bp and 1043 bp in length, respectively, The IGS2 has an
imperfect direct repeat (type 1) homologous to the region downstream
to the 5S rRNA gene and three imperfect tandem direct repeats (type 2)
upstream to the SSU rRNA-encoding sequence. Structural analysis by a
comparative method showed that the overall secondary structure of the
SSU rRNA is generally similar to that of S, cerevisiae, whereas the se
condary structures of the V4 regions predicted by the thermodynamics-b
ased method showed different configurations between distantly related
taxa, implying that these structural differences can provide phylogene
tically informative features. Phylogenetic trees based on both the ali
gned SSU rRNA sequences with almost full-length sequences and V4 seque
nces revealed that T. matsutake is very closely related to other basid
iomycetes belonging to Agaricales. Thus we propose that the V4 region
is also a good source for the inference of phylogeny to support the SS
U rRNA phylogeny.