2 Results and analysis
2.1 Genome structures and characteristics
The chloroplast genomes of all eight species of Cyatheaceae are
double-stranded, closed, circular molecules with a typical tetrad
structure (with Alsophila denticulata as an example, as shown in
Figure 1). The genome length ranges from 154,046 bp (Alsophila
denticulata ) to 166,151 bp (Alsophila gigantea ). The structure
includes a large single-copy region (LSC) (bp 85975–92315), a small
single-copy region (SSC) (bp 23245–28874), and an inverted repeat
region (IR) (bp 23245–28874), of which IRA and IRB are two inverted
repeat regions. The GC content of each region of the chloroplast genome
of different species varied little, the total GC content ranging from
40.3% to 41.9% (Table 1). Only LSC, SSC, and one IR were analyzed. The
chloroplast genome of each species of Cyatheaceae contained 117 genes,
which encoded 85 proteins, four rRNAs, and 28 tRNAs. Pseudogenes
(ycf66, trnT-UGU ) were also present in these genomes. Among these
genes are 13 genes located in the IR region. The ndhB gene spans
the LSC and IRA regions, and there is a duplicated exon 2 sequence of
the ndhB gene near the boundary of the IRB. Twelve genes have one
intron, and three genes (ycf3 , clpP , and rps12 )
have two introns.