Comparative phylogenetic analysis of complete plastid genomes of Renanthera (Orchidaceae).

Owing to its attractive flower shape and color, Renanthera (Orchidaceae), comprising about 19 species, has significant ornamental value as a houseplant, in floral design and in landscape gardens. Two species of Renanthera are categorized as endangered and critically endangered in China's Red List and international trade in these orchids is currently strictly monitored by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This paper reports on the de novo assembled and annotated plastome of four species of Renanthera; R. citrina, R. coccinea, R. imschootiana, and R. philippinensis. The length of the plastome sequences ranged from 144,673 bp (R. imschootiana) to 149,007 bp (R. coccinea) with GC content of 36.6-36.7%. The plastomes showed a typical quadripartite structure, including a large single-copy (84,241-86,404 bp), a small single-copy (11,468-12,167 bp), and a pair of inverted repeats (24,482-25,715 bp) regions. Of the 120 genes detected, 74 were protein coding, 38 were tRNA, and eight were rRNA genes. The plastome of Renanthera is rather conserved, but nucleotide variations that could distinguish them apart are noticeable-the total number of tandem repeats ranged from 62 (in R. imschootiana) to 74 (in R. citrina); while the number of long repeats ranged from 21 (in R. imschootiana and R. philippinensis) to 43 (in R. citrina). Three hypervariable regions (psbI-trnS-GCU, trnG-GCC, rpl32) were identified. Phylogenetic analyses based on the CDS using maximum likelihood (ML) and Bayesian inference (BI) revealed that Renanthera is closely related to Holcoglossum, Neofinetia, Pendulorchis, and Vanda. The relationship between the four species of Renanthera was fully resolved; a monophyletic clade was formed and R. coccinea was recorded as the first to diverge from the rest. The genetic data obtained from this study could serve as a useful resource for species identification in Renanthera as well as contribute to future research on the phylogenomics of Orchidaceae.

The complete chloroplast genome of Diarthron tianschanicum (Thymelaeaceae).

Diarthron tianschanicum (Pobedimova) Kit Tan (Thymelaeaceae), a perennial herb, has been used as counterfeit for Stellera chamaejasme in traditional Chinese folk medicine. In this study, the complete chloroplast genome sequence of D. tianschanicum is reported for the first time. The plastome, 172,119 bp in length, is quadripartite and circular. It contains a large single-copy (LSC) region (85,829 bp), a small single-copy (SSC) region (2828 bp), and two separate inverted repeat (IR) regions (41,731 bp). The overall GC content of the complete chloroplast genome is 36.8%. The genome contains 139 genes, including 93 protein-coding, 38 tRNA genes, and eight rRNA genes. The phylogenetic tree showed that all sampled species of Thymelaeaceae formed a monophyletic clade. D. tianschanicum was closely related to the congeneric D. linifolium and formed a monophyly with 100% support.

Complete plastomes of six species of Wikstroemia (Thymelaeaceae) reveal paraphyly with the monotypic genus Stellera.

Wikstroemia (Thymelaeaceae) is a diverse genus that extends from Asia to Australia and has been recorded on the Hawaiian Islands. Despite its medicinal properties and resource utilization in pulp production, genetic studies of the species in this important genus have been neglected. In this study, the plastome sequences of six species of Wikstroemia were sequenced and analysed. The plastomes ranged in size between 172,610 bp (W. micrantha) and 173,697 bp (W. alternifolia) and exhibited a typical genome structure consisting of a pair of inverted repeat (IR) regions separated by a large single-copy (LSC) region and a small single-copy (SSC) region. The six plastomes were similar in the 138 or 139 genes predicted, which consisted of 92 or 93 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. The overall GC contents were identical (36.7%). Comparative genomic analyses were conducted with the inclusion of two additional published species of Wikstroemia in which the sequence divergence and expansion of IRs in the plastomes were determined. When compared to the coding sequences (CDSs) of Aquilaria sinensis, five genes, namely, rpl2, rps7, rps18, ycf1 and ycf2, indicated positive selection in W. capitata. The plastome-based phylogenetic analysis inferred that Wikstroemia in its current state is paraphyletic to Stellera chamaejasme, while the ITS-based tree analyses could not properly resolve the phylogenetic relationship between Stellera and Wikstroemia. This finding rekindled interest in the proposal to synonymize Stellera with Wikstroemia, which was previously proposed but rejected due to taxonomic conflicts. Nevertheless, this study provides valuable genomic information to aid in the taxonomic implications and phylogenomic reconstruction of Thymelaeaceae.

The complete chloroplast genome of Pleione maculata, an orchid with important ornamental value and medicinal value.

Pleione maculata is an epiphytic orchid with significant ornamental value and medicinal value. Here, we report the first complete chloroplast genome of P. maculata. The circular genome was 158,394 bp in length and consisted of a pair of inverted repeats (IR 26,646 bp), which were separated by a large single copy region (LSC 86,603 bp) and a small single copy region (SSC 18,499 bp). It contained 135 genes, including 89 protein-coding genes, 38 tRNAs and 8 rRNAs. Phylogenetic analysis of cp genomes from 41 species of Orchidaceae revealed that all species of Pleione formed one monophyletic clade and P. maculata was located at the base of the genus with high bootstrap values (≥99.1%).

The complete chloroplast genome of Hydrangea davidii (Hydrangeaceae).

Hydrangea davidii, a perennial shrub of Hydrangeaceae, is an ornamental plant endemic to China. Here, we report the complete chloroplast genome of H. davidii. The complete chloroplast genome is totally 158,054 bp in length with a typical quadripartite structure. It consists a pair of inverted regions (IRs) of 26,140 bp, which were separated by a large single copy (LSC) region of 87,008 bp and a small single copy (SSC) region of 18,766 bp, respectively. The chloroplast genome encoded 131 genes, including 85 protein-coding genes, 8 rRNA genes and 38 tRNA genes. The GC content in the whole cp genome, LSC region, SSC region, and IR region are 37.8%, 36.0%, 31.7%, and 43.1%, respectively. In total, 49 SSRs were identified in the complete chloroplast genome. Phylogenetic analysis showed that H. davidii is closely related to Hydrangea platyarguta with a support rate of 100%.