Phylogenetic analysis and predicted secondary structures of the rDNA internal transcribed spacers of the powdery mildew fungi (Erysiphaceae) |
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Authors: | Susumu Takamatsu Tetsuya Hirata Yukio Sato |
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Institution: | (1) Faculty of Bioresources, Mie University, Kamihama-cho, Mie 514-8507 Tsu, Japan;(2) Toyama Prefectural University, Kosugi-Cho, 939-0398 Toyama, Japan |
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Abstract: | The nucleotide sequences of the internal transcribed spacer (ITS) regions of the ribosomal DNA including the 5.8S rRNA gene
and the 5′ end of the 28S rRNA gene have been determined for 19 species in 10 genera of the powdery mildew fungi in order
to analyze their phylogenetic relationship. These fungi were divided into two large groups based on the nucleotide length
of the ITS regions, and this grouping was in line with that based on the morphological characters of the anamorphic stage
rather than the teleomorphic stage. Although the variable ITS sequences were often ambiguously aligned, conserved sites were
also found. Thus, a neighbor-joining tree was constructed using the nucleotide sequence data of the conserved sites of the
ITS regions, the 5.8S rRNA gene, and the 5′ end of the 28S rRNA gene. The phylogenetic tree displayed the presence of four
groups in the powdery mildews, which were distinguished by their morphology and/or host ranges. In the ITS2 region, the presence
of a common secondary structure having four hairpin domains was suggested, in spite of the highly variable nucleotide sequences
of this region. The predicted secondary structure was supported by the compensatory mutations as well as compensatory conserved
sequences and high G+C content in the predicted stem regions.
Contribution No. 142 from the Laboratory of Plant Pathology, Mie University. |
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Keywords: | Erysiphaceae internal transcribed spacer phylogeny powdery mildew secondary structure |
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