Distributions of introns in streptophyte cpDNAs. Circles denote the presence of group I introns, and squares denote the presence of group II introns. Divided squares represent trans-spliced group II introns. Open symbols denote the absence of intron ORFs, whereas filled symbols denote their presence. Intron insertion sites in protein-coding and tRNA genes are given relative to the corresponding genes in Mesostigma cpDNA; the insertion site in rrl is given relative to the Escherichia coli 23S rRNA. For each insertion site, the position corresponding to the nucleotide immediately preceding the intron is reported. Note that rps16 is lacking in Marchantia cpDNA and that the rrl intron at position 2593 is absent from all completely sequenced land plant cpDNAs, with the exception of Anthoceros cpDNA. The intron data were taken from the following accession numbers: Staurastrum, [GenBank:AY958085]; Zygnema, [GenBank:AY958086]; Chaetosphaeridium, [GenBank:NC_004115]; Marchantia, [GenBank:NC_001319]; and Anthoceros formosae [GenBank:NC_004543].