Nucleotide Sequence of the Internal Transcribed Spacers of Ribosomal DNA inPicea AbiesKarst

Abstract

The nucleotide sequences of the internal transcribed spacers (ITS1 and ITS2) of ribosomal DNA from Picea abies are reported. Two types of ITS1 of 2784 bp and 3271 bp long exist, whereas only one ITS2 type 238 bp long is present in this species. The shorter ITS1 is characterized by three shorter subrepeats: ssr1, ssr2 and ssr3, 221 bp, 227 bp and 226 bp long respectively. Between the ssr1 and ssr2 sub-repeats are inserted three longer sub-repeats: LSR1, LSR2 and LSR3, 480 bp, 480 bp and 581 bp long respectively. The similarity between the three ssr range from 66% to 79% and between the three LSR range from 65% to 96%. At the end of the LSR3 a microsatellite of 14 CT elements is present. The longer ITS1 type is due to a duplication of the LSR1, most probably obtained by unequal crossing-over and it has an identity of 97.3% with the shorter ITS1 type.

Variation in the nrDNA ITS of Pinus Subsection Cembroides: Implications for Molecular Systematic Studies of Pine Species Complexes

“…The ITS region of subgenus Strobus shares many similarities with other available complete ITS sequences from Pinaceae, which are limited to P. pinea (Marrocco et al, 1996), Larix, and Pseudotsuga (Gernandt and Liston, 1999). Table 2 also includes length and GC content statistics for complete ITS1 and ITS2 sequences for Picea abies (Maggini et al, 2000) and complete 5.8S and ITS2 sequences for three North American species of Picea, P. glauca, P. mariana, and P. rubens (Germano and Klein, 1999). In the present study, 19 Pinus clones were completely sequenced, although final sequences from the tandem subrepeat region were based primarily on single-strand reads.…”

“…Values in parentheses are standard deviations. Values for Picea are based on 2 (complete) ITS1 sequences for P. abies (Maggini et al, 2000), 12 5.8S sequences for P. glauca, P. mariana, and P. rubens (Germano and Klein, 1999), and 13 ITS2 sequences for P. abies, P. glauca, P. mariana, and P. rubens. Total ITS region lengths for Picea are based on P. abies and assume a 5.8S length of 162 bp.…”

“…Up to one half of the ITS1 length in Pinaceae is made up of subrepeats, most of which occur near the 3Ј end of the spacer (Marrocco et al, 1996;Vining and Campbell, 1997;Gernandt and Liston, 1999;Maggini et al, 2000). Although some conserved portions of ITS1 and ITS2 have been shown to be involved in pre-rRNA processing, most appear to be free of selective constraints.…”

“…The ITS region (ITS1, ITS2, and 5.8S gene) is exceptionally long in Pinaceae, ranging from approximately 1550 bp in Pseudotsuga to between 3150 and 3660 bp in Picea (Liston et al, 1996;Germano and Klein, 1999;Maggini et al, 2000). Up to one half of the ITS1 length in Pinaceae is made up of subrepeats, most of which occur near the 3Ј end of the spacer (Marrocco et al, 1996;Vining and Campbell, 1997;Gernandt and Liston, 1999;Maggini et al, 2000).…”

“…Variation in tandem subrepeat number is not limited to subsections of Pinus. Excluding the dispersed subrepeat 0, there are four or five (tandem) subrepeats within Pinus, one in Larix, two in Pseudotsuga (Gernandt and Liston, 1999), and two in Picea (Maggini et al, 2000). The most likely site of recombination, particularly between nonhomologous subrepeats, may be the highly conserved core sequence, 5Ј-GGTGGCCAC-CCTAGTCT-3Ј.…”