These results point to the possibility that these insertions are group 1 introns. Figure 1 Amplification pattern by RT-PCR with the site-specific primer pairs

for intron-F and G. PCR products of from cDNA amplified with the primers inF-F and inF-R are eluted in lanes 2, 3, 15 and 16, and with primers inG-F and inG-R in lanes 4 and 5. PCR products from genomic DNA amplified with primer pair for intron-F are eluted in lanes 6, 7, 10, 13 and 14, and with primer pair for intron-G in lanes 8, 9 and 11. Lane 12 is the negative control. Moreover, we analyzed sequences of the spliced introns to confirm the boundaries of exon and intron sequences. The last nucleotide of the upstream learn more exon was click here confirmed to be a T (U in RNA) and the last nucleotide of the intron was a G, consistent with group 1 introns [11, 12]. Phylogenetic relationships of introns F and G of P. verrucosa Sequences of intron-F and G of ten P. verrucosa strains were sequenced and it was found that DNA sequence polymorphisms exist among the two introns, i.e., the intron-Fs ranged in the size from 389 to 391 bps and the four intron-Gs from 389 to 393 bps shown in Table 2. There were 24

nucleotide substitutions and two deletions/insertions (TH9 strain) within intron-F. There were five nucleotide substitutions among intron-Gs from PV1, PV33 and PV34, unlike 36 substitutions between PV1 and PV3. In addition, Blast search analyses and alignment lead us to believe that intron-Fs and Gs from 14 introns belong to subgroup IC1 of group 1 intron. Fourteen introns from 12 representative strains of P. verrucosa including Tetrahymena thermophila as out-group were aligned and used for phylogenetic analyses. Neighbor-joining (NJ) and Maximum Parsimony (MP) trees based on the alignment of these intron sequences are shown in Figure 2. The data set consisted of 466 characters, of which 156 were removed from the MP analysis due

to ambiguous alignment. Of the remaining 310 characters, 201 were variable and 129 were phylogenetically informative for parsimony analysis. Three major distinct and well-supported clades that had homologous topology were obtained from both phylogenetic analysis methods showing Protein kinase N1 that all the introns analyzed were undergoing a similar rate of evolution. The first clade [I] (87% BS support in NJ, 81% in MP) consisted of six strains having intron-F including 3 clinical isolates, the second clade [II] (57% BS in NJ and 77% in MP) consisted of 4 strains having intron-F, and the third clade [III] (100% BS in both trees) consisted of four G introns. All the introns clustered in clades [I] and [II] are inserted at the same position L798 those in clade [III] at the same position L1921. Introns inserted at the same positions belong to the same clusters and are considered to be the same subgroups.