Chloroplast Genome Analysis of Two Medicinal Coelogyne spp. (Orchidaceae) Shed Light on the Genetic Information, Comparative Genomics, and Species Identification.

Although the medicinal properties of Coelogyne spp. have been previously studied, there is little genomic information providing a valuable tool for the plant taxonomy, conservation, and utilization of this genus. This study used the next-generation MiSeq sequencing platform to characterize the chloroplast (cp) genomes of Coelogyne fimbriata and Coelogyne ovalis. The Maximum Likelihood (ML) and Bayesian (BI) methods were employed to confirm the phylogenetic position of two Coelogyne species based on the whole chloroplast genome sequences. Additionally, we developed eight new primers based on the two cp genomes' medium variable regions and evaluated the transferability to another 16 Coelogyne species. We constructed phylogenetic trees including 18 Coelogyne species and four outgroup species using the chloroplast fragments with the ML method. Our results showed that the cp genomes of C. fimbriata and C. ovalis contained a small single-copy region (18,839 and 18,851 bp, respectively) and a large single-copy region (87,606 and 87,759 bp, respectively), separated by two same-length inverted-repeat regions (26,675 bp in C. fimbriata and 26,715 bp C. ovalis, respectively). They all contained 86 protein-coding genes, 38 tRNA genes, and eight rRNA genes, revealing strong structure and gene content similarities. The phylogenetic analysis indicated a close relationship between the genera Coelogyne and Pleione. The newly developed primers revealed good transferability among the Coelogyne taxa and provided enough variable sites to distinguish C. fimbriata and C. ovalis. The two complete cp genomes and the eight new primers of Coelogyne provide new genomic data for further studies on phylogenomics, population genetics, and evolutionary history of Coelogyne taxa.

Chloroplast genome structure and phylogenetic position of Calanthe sylvatica (Thou.) Lindl. (Orchidaceae).

Calanthe sylvatica plays an important role in horticulture and is undergoing the pressure of population decline. In this study, its complete chloroplast genome sequence was successfully obtained by the technology of Illumina sequencing. The whole chloroplast genome length was 158,828 bp with a typical quadripartite structure: one large single copy (LSC) region (87,277 bp), one small single copy (SSC) region (18,535 bp) and a pair of inverted repeats (IR) regions (26,508 bp). The GC content of this genome was 36.7%. The genome contained 118 genes consisting of 84 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. The phylogenetic analysis indicated a close relationship between C. sylvatica and Calanthe triplicata.