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Predicted secondary structure of Gaeumannomyces graminis var. tritici isolate WF9039 group I intron RNA. Intron sequences are in uppercase letters, exon sequences are in lowercase letters, and arrows denote the 5 and 3 splice sites. Bold letters indicate group I intron conserved sequence elements labeled as P, Q, R, and S. Insert: putative internal guiding site (IGS) sequences forming paired segments P1 and P10 are shown in box.
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The length of the small subunit ribosomal DNA (SSU rDNA) differs among isolates of species and varieties of Gaeumannomyces. The sequence of the 3′ region of the SSU rDNA revealed 340-, 365-, and 520-bp insertions for G. graminis varieties avenae, tritici, and graminis, respectively. The intron sequences from varities tritici and avenae were similar...
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... sequence and structural elements. A puta- tive group I intron, like the RNA secondary structure, has been generated from the sequence of the 365-bp insertion in the small subunit rDNA of WF9039 isolate of Ggt (Fig. 3). The predicted secondary structure of the 520-bp insertion of isolate WF9238 (Ggg) was similar to that of the Ggt intron, except that the former has an extra 155 bp at the 3 end (Fig. ...
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Citations
... Previous studies demonstrated that oats and wheat take-all fungi are closely related but separated from G. graminis (Walker 1972, 1981, Bryan et al. 1995, Fouly & Wilkinson 2000, Saleh & Leslie 2004. Gaeumannomyces tritici and G. avenae are more virulent species and have simple hyphopodia, but ascospores are larger in G. avenae (Walker 1972). ...
Take-all disease of Poaceae is caused by Gaeumannomyces graminis (Magnaporthaceae). Four varieties are recognised in G. graminis based on ascospore size, hyphopodial morphology and host preference. The aim of the present study was to clarify boundaries among species and varieties in Gaeumannomyces by combining morphology and multi-locus phylogenetic analyses based on partial gene sequences of ITS, LSU, tef1 and rpb1. Two new genera, Falciphoriella and Gaeumannomycella were subsequently introduced in Magnaporthaceae. The resulting phylogeny revealed several cryptic species previously overlooked within Gaeumannomyces. Isolates of Gaeumannomyces were distributed in four main clades, from which 19 species could be delimited, 12 of which were new to science. Our results show that the former varieties Gaeumannomyces graminis var. avenae and Gaeumannomyces graminis var. tritici represent species phylogenetically distinct from G. graminis, for which the new combinations G. avenae and G. tritici are introduced. Based on molecular data, morphology and host preferences, Gaeumannomyces graminis var. maydis is proposed as a synonym of G. radicicola. Furthermore, an epitype for Gaeumannomyces graminis var. avenae was designated to help stabilise the application of that name.
... This was due to insertions of non-coding sequences in one or two positions in the middle region of the SSU rDNA. At one position, the insertion belonged to a group I intron with a characteristic secondary structure (Fouly and Wilkinson 2000). At the other position, the sequence insertions were found only in isolates of G. g. var. ...
... Fifty-four isolates, representing three varieties of Gaeumannomyces graminis, G. incrustans and Magnaporthe poa were collected mainly from North America and used in this study.Table 1 lists the cultures, their isolate number, and their geographic origin. Morphological and molecular methods and pathogenicity tests were used to characterize the isolates (Walker 1981; Henson 1989 Henson , 1992 Elliott 1991; Wilkinson and Pedersen 1993; Fouly et al. 1996; Fouly and Wilkinson 2000). Cultures were maintained on 1/5th strength potato dextrose agar. ...
Gaeumanoumyces graminis (Gg) varieties (tritici, avenae and graminis) were found to possess sequence insertions in the middle region of the small subunit ribosomal DNA. The sequence insertions
were used to distinguish Gg isolates from North America obtained from wheat, creeping bentgrass and St. Augustinegrass and to resolve their phylogenetic
relationship. Based on the alignment of sequence insertions, Gg isolates were divided into two sets: set I contained all isolates of Ggt; Gga; and Ggg isolates WF 9124, WF 9238, and WF 9463; while set II contained the other Ggg isolates that possessed insertion sequences with different lengths. Phylogenetic analysis of sequence insertions from set
I shows that Ggt are more closely related to Gga that is supported by bootstrap 85%. Ggg isolates did not form a distinct group and appeared mixed between the well supported Ggt and Gga groups. Parsimony analysis of Ggg set II insertions revealed a distinct clade consisting of three monophyletic groups.
KeywordsGroup I intron–Take-all disease–Small subunit rDNA–
Gaeumannomyces graminis
... Nucleotide insertions such as spliceosomal introns, degenerate group I introns, and group I introns have been reported in nuclear ribosomal DNA (rDNA) of fungi including basidiomycetes (Hibbett 1996), a mycorrhizal deuteromycete (Shinohara et al. 1996), anamorphs of fungi parasitic on insects (Ito & Hirano 1999), plant pathogenic ascomycetes (Suga et al. 2000;Fouly & Wilkinson 2000;Gibb & Hausner 2003), and lichenized ascomycetes ( Gargas et al. 1995;Grube et al. 1996;1999;Ivanova et al. 1998;Stenroos & DePriest 1998;Thell 1999;Myllys et al. 1999Myllys et al. , 2002Bhattacharya et al. 2002). The first report of group I intron-like insertions in lichen fungi was from the Cladonia chlorophaea (Flörke ex Sommerf.) ...
During a study on population genetics of three species of Cladonia using the nuclear ribosomal 18S DNA, two species contained group I intron-like sequences located in positions 788 and 940 with reference to the E. coli 16S rDNA gene. The intron in position 940 was not typical of group I introns and had previously been described only from the Parmeliaceae and Lecanoraceae, but here we report the occurrence of this intron in the Cladoniaceae. The intron in position 788 had characteristics of group I introns and had previously been reported from the Physciaceae. In this paper we provide for the first time a putative RNA fold for the nS788 intron, compare the secondary RNA structure of the Cladonia group I introns (nS788 and nS940) to that of other taxa, and infer a phylogenetic history among 15 members of the Lecanorales based on the evolutionary history of the nS788 group I intron. The RNA fold for nS788 contained two optional hairpins, P2.1 and a potentially newly described hairpin referred to as P5.1. The phylogenetic hypothesis supports the monophyly of the genus Cladonia. It also supports the separation of two large groups in the Physciaceae; the Buellia-group and the Physcia-group.
... PCR product size and /or restriction site polymorphisms in the ITS region and 18S rRNA gene of the nuclear rDNA can be used to identify Geaumannomyces species and varieties of G. graminis (Fouly et al., 1997;Ward and Akrofi, 1994). Size variation in nuclear 18S and 26S rRNA gene PCR products was found to be due to presence/absence and size variation of group I introns (Fouly and Wilkinson, 2000a;Tan and Wong, 1996). Size variation of 18S rRNA gene introns was used to differentiate between isolates of Ggt, Gga, Ggg, G. incrustans, G. cylindrosporus and Ophioceras leptosporum (misnamed G. leptosporus in Fouly et al., 1997). ...
SUMMARY Take-all, caused by the fungus Gaeumannomyces graminis var. tritici, is the most important root disease of wheat worldwide. Many years of intensive research, reflected by the large volume of literature on take-all, has led to a considerable degree of understanding of many aspects of the disease. However, effective and economic control of the disease remains difficult. The application of molecular techniques to study G. graminis and related fungi has resulted in some significant advances, particularly in the development of improved methods for identification and in elucidating the role of the enzyme avenacinase as a pathogenicity determinant in the closely related oat take-all fungus (G. graminis var. avenae). Some progress in identifying other factors that may be involved in determining host range and pathogenicity has been made, despite the difficulties of performing genetic analyses and the lack of a reliable transformation system.
Ribosomal DNA (rDNA) containing small subunit (SSU) rDNA and both flanking regions in the entomopathogenic microsporidian Nosema bombycis NIS 001 was amplified from genomic DNA with a primer set based on the sequence of an inverse polymerase chain reaction (PCR)-derived fragment. In this fragment, SSU rDNA was divided by a 618-bp insert at nt 599, and 5S rDNA was located downstream of the SSU rDNA, fragmented by 284-bp intergenic spacer. In addition, the 48-bp 3'-end of large subunit (LSU) rDNA was located 118 bp upstream of the fragmented SSU rDNA. In the amplicon, the region upstream of the LSU rDNA was a homologue of the C-terminal CHARLIE8 transposon-like element of human GTF2IRD2. In this organism, another fragmented SSU rDNA, which was divided by a 231-bp insert at nt 50, was also detected. Both the intact (insertless) and fragmented SSU rDNAs clustered with LSU rDNA and 5S rDNA and the intergenic sequences between SSU rDNA and 5S rDNA were divergent in an organism. Reverse transcription (RT)-PCR assay indicated that not only the intact SSU rDNA but also the fragmened SSU rDNA were transcribed in N. bombycis.
