Loading…
Plastome Evolution and Phylogeny of Orchidaceae, With 24 New Sequences
In order to understand the evolution of the orchid plastome, we annotated and compared 124 complete plastomes of Orchidaceae representing all the major lineages in their structures, gene contents, gene rearrangements, and IR contractions/expansions. Forty-two of these plastomes were generated from t...
Saved in:
| Published in: | Frontiers in plant science 2020-02, Vol.11, p.22-22 |
|---|---|
| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | In order to understand the evolution of the orchid plastome, we annotated and compared 124 complete plastomes of Orchidaceae representing all the major lineages in their structures, gene contents, gene rearrangements, and IR contractions/expansions. Forty-two of these plastomes were generated from the corresponding author's laboratory, and 24 plastomes-including nine genera (
,
,
,
,
,
,
, and
)-are new in this study. All orchid plastomes, except
and
have a quadripartite structure consisting of a large single copy (LSC), two inverted repeats (IRs), and a small single copy (SSC) region. The IR region was completely lost in the
plastomes. The SSC is lost in the
plastome. The smallest plastome size was 19,047 bp, in
and the largest plastome size was 178,131 bp, in
. The small plastome sizes are primarily the result of gene losses associated with mycoheterotrophic habitats, while the large plastome sizes are due to the expansion of noncoding regions. The minimal number of common genes among orchid plastomes to maintain minimal plastome activity was 15, including the three subunits of
(14, 16, and 36), seven subunits of
(2, 3, 4, 7, 8, 11, and 14), three subunits of
(5, 16, and 23),
C-GCA, and
P genes. Three stages of gene loss were observed among the orchid plastomes. The first was
gene loss, which is widespread in Apostasioideae, Vanilloideae, Cypripedioideae, and Epidendroideae, but rare in the Orchidoideae. The second stage was the loss of photosynthetic genes (
,
and
) and
gene subunits, which are restricted to
and some species of
and
. The third stage was gene loss related to prokaryotic gene expression (
,
,
and others), which was observed in
,
,
and
In addition, an intermediate stage between the second and third stage was observed in
(Vanilloideae). The majority of intron losses are associated with the loss of their corresponding genes. In some orchid taxa, however, introns have been lost in
16
16, and
P(2) without their corresponding gene being lost. A total of 104 gene rearrangements were counted when comparing 116 orchid plastomes. Among them, many were concentrated near the IRa/b-SSC junction area. The plastome phylogeny of 124 orchid species confirmed the relationship of {Apostasioideae [Vanilloideae (Cypripedioideae (Orchidoideae, Epidendroideae))]} at the subfamily level and the phylogenetic relationships of 17 tribes were also established. Molecular clock analysis based on the whole plastome sequences suggested that Orchidaceae diverged from its |
|---|---|
| ISSN: | 1664-462X 1664-462X |
| DOI: | 10.3389/fpls.2020.00022 |