The complete chloroplast DNA sequences of the charophycean green algae Staurastrum and Zygnema reveal that the chloroplast genome underwent extensive changes during the evolution of the Zygnematales

Table 1 General features of cpDNAs from Staurastrum, Zygnema, other streptophytes and Mesostigma

Feature	Mesostigma	Staurastrum	Zygnema	Chaetosphaeridium	Marchantia
Size^a (bp)
IR	6,057	-	-	12,431	10,058
SSC	22,619	-	-	17,639	19,813
LSC	83,627	-	-	88,682	81,095
Genome	118,360	157,089	165,372	131,183	121,024
A+T content (%)	69.9	67.5	68.9	70.4	71.2
Gene content^b	136	121	125	125	120
Introns
Group I	0	1	1	1	1
Group II
Cis-spliced	0	6	11	16	18
Trans-spliced	0	1	1	1	1

^a Because Staurastrum and Zygnema cpDNAs lack an IR, only the genome size is given for each of these cpDNAs. SSC, small single-copy region; LSC, large single-copy region.
^b Unique ORFs, intron ORFs and pseudogenes were not taken into account. Note that Chaetosphaeridium tufA was considered to be a functional gene.