title: [Group-I introns in 18S rDNA of Cenococcum geophilum Fr].
abstract: OBJECTIVE
  To analyze the sequences and secondary structure of group-I introns in 18S rDNA of Cenococcum geophilum, and to study the factors effecting Cg genetic diversity.
  
  
  METHODS
  The 3' end region of 18S rDNA were amplified from twenty-three Cg isolates, and the PCR fragments from thirteen isolates were sequenced. The Neighbor-Joining phylogenetic analyses were performed using MAGE version 4.0, and the secondary structures of the Cg introns were predicted using Mfold.
  
  
  RESULTS
  The results showed that fourteen out of nineteen Cg isolates originated in China had group-I introns in 18S rDNA. Their sequences, ranging in size from 488 to 590 nucleotides, were from 92.3% to 100% similar to each other from our data and GenBank data. The 5' end sequences of the introns were conserved, while the 3' end sequences were variable. The analysis of secondary structure indicated all the introns from forty-five Cg isolates contained ten pairing regions (P1-P10). The P5 region was composed of P5, P5a, P5b, P5c and P5d, and there were two extra pairing stems (P9. 1, P9. 2) besides the 3' end of P9.
  
  
  CONCLUSIONS
  It was suggested that Cg had rich genetic diversity, and we did not found the relationship between Cg genetic variation and its geographical and host origination.
authors.affiliation: College of Agronomy, Inner Mongolia Agricultural University, Hohhot 010019, China. wangting060308@163.com
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Lihong
authors.initials: L
authors.lastname: Chen
mesh_terms: D001203:Ascomycota / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics*; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D010944:Plants / Q000382:microbiology; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S