For RT-PCR of intron-G, primer pair inG-F and inG-R was used. RT-PCR was carried out in the following conditions: cDNA synthesis at 55°C for 30 min, denaturation at 94°C for 2 min, and PCR amplification at 40 cycles of 94°C for 15 sec, 55°C for 30 sec and 68°C for 1.5 min and final extension at 68°C

for 5 min. Amplification products were eluted in 3.5% polyacrylamide gel in tris-acetate-EDTA buffer on an electrophoresis run condition of 100 V for 30 min and followed by 75 V for 25 min, INK 128 in vitro together with genomic DNAs amplified with the same primer pairs as control (shown in Figure 1). The RT-PCR products were purified with the SUPREC-PCR (TAKARA Bio Inc, Sigma, Japan) and ligated into the pGEM-T Easy Vector System (Promega, Madison, WI, USA). Plasmids were transformed into E. coli competent cells (ECOS TM Competent E. coli, JM109, NIPPON GENE Co., LTD., Japan). Transconjugants were selected on LB agar plates containing 50 μg/ml ampicilin and 40 μg/ml of 5-bromo-4-chloro-3-indoyl-β-D-galactopyranoside (X-Gal). The presence of the expected insert was confirmed by PCR and agarose gel electrophoresis. The inserts were sequenced with T7 (5′-TAATACGACTCACTATAGGG-3′) and M13 reverse primers (5′-AGGAAACAGCTATGACCATGA-3′).

Phylogenetic analysis of introns from P. verrucosa Nucleotide sequences were aligned using the BioEdit program version 7.0.9.0 [37]. For phylogenetic analysis, alignment gaps were treated as Obatoclax Mesylate (GX15-070) missing Lumacaftor data and ambiguous positions were excluded from the analysis. NJ analysis [38] as distance matrix method and MP analysis as character state method were carried out using PAUP 4.0b10 [39]. For NJ analysis, the distances between sequences were calculated using Kimura’s two-parameter model [40]. MP analysis was undertaken with the heuristic search option using the tree-bisection-reconstruction

(TBR) algorithm with 1000 random sequence additions to find the global optimum tree. All positions were treated as unordered and unweighted. The maximum tree number was set at 104. To estimate clade support, the bootstrap procedure of Felsenstein [41] was employed with 1000 replicates in both MP and NJ analyses. Bootstrap (BS) values higher than 50% are indicated. Alignment and phylogenetic analysis of core sequences For the comparison with highly conserved sequences of subgroup IC1 from 20 taxa, sequences of elements of P, Q, R and S and the pairing segment P3 were obtained from DDBJ database (accession numbers shown after sample name in Figure 3). These regions do not include IGS, because the sequences in the upstream region of intron insertion positions do not share a common IGS [42]. The NJ tree was constructed after alignment of all the sequences, which ranged from 57 to 60 bps (Additional File 2). Insertion positions are shown after the sample ID or accession number. The insertion position numbering of the taxa refers to the 23S nucleotide sequence of E.