Variability of Nuclear SSU-rDNA Group Introns Within Septoria Species: Incongruence with Host Sequence Phylogenies |
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Authors: | Nicolas Feau Richard C Hamelin Louis Bernier |
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Institution: | (1) Centre d’étude de la forêt, Université Laval, Québec, G1K 7P4, Canada;(2) Service canadien des forêts, Ressources naturelles Canada, Centre de foresterie des Laurentides, 1055 du PEPS, P.O. Box 3800, Québec, G1V 4C7, Canada |
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Abstract: | We report structural features and distribution patterns of 26 different group I introns located at three distinct nucleotide
positions in nuclear small subunit ribosomal DNA (SSU-rDNA) of 10 Septoria and 4 other anamorphic species related to the teleomorphic genus Mycosphaerella. Secondary structure and sequence characteristics assigned the introns to the common IC1 and IE groups. Intron distribution
patterns and phylogenetic relationships strongly suggested that some horizontal transfer events have occurred among the closely
related fungal species sampled. To test this hypothesis, we used a comparative approach of intron- and rDNA-based phylogenies
through MP- and ML-based topology tests. Our results showed two statistically well-supported major incongruences between the
intron and the equivalent internal transcribed spacer (ITS) tree comparisons made. Such absence of a co-evolutive history
between group I introns and host sequences is discussed relatively to the intron structures, the mechanisms of intron movement,
and the biology of the Mycosphaerella pathogenic fungi.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Reviewing Editor: Debashish Bhattacharya |
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Keywords: | Group I introns Fungi Septoria Pseudocercospora Mycosphaerella Small subunit ribosomal DNA Horizontal transfer RNA secondary structure |
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