The marvelously diverse Orchidaceae constitutes the largest family of angiosperms. The genus Cymbidium in Orchidaceae is well known for its unique vegetation, floral morphology, and flower scent traits. Here, a chromosome-scale assembly of the genome of Cymbidium ensifolium (Jianlan) is presented. Comparative genomic analysis showed that C. ensifolium has experienced two whole-genome duplication (WGD) events, the most recent of which was shared by all orchids, while the older event was the τ event shared by most monocots. The results of MADS-box genes analysis provided support for establishing a unique gene model of orchid flower development regulation, and flower shape mutations in C. ensifolium were shown to be associated with the abnormal expression of MADS-box genes. The most abundant floral scent components identified included methyl jasmonate, acacia alcohol and linalool, and the genes involved in the floral scent component network of C. ensifolium were determined. Furthermore, the decreased expression of photosynthesis-antennae and photosynthesis metabolic pathway genes in leaves was shown to result in colorful striped leaves, while the increased expression of MADS-box genes in leaves led to perianth-like leaves. Our results provide fundamental insights into orchid evolution and diversification.

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Goodyera foliosa is a terrestrial orchid in Asia and has been listed as an endangered species in the Red List. In this study, we assembled the complete chloroplast genome of G. foliosa using Illumina sequencing data. Its full-length of 154,008 bp including a pair of invert repeats (IR) regions of 25,045 bp, large single-copy (LSC) region of 83,248 bp, and small single-copy (SSC) region of 20,670 bp. The chloroplast genome contains 127 genes, including 80 protein-coding genes, 39 tRNA genes, and 8 rRNA genes. In addition, the phylogenetic analysis base on 12 chloroplast genomes of Orchidaceae indicates that G. schlechtendaliana is closely related to G. foliosa. Our study would be helpful for the formulation of conservation strategies and further research of G. foliosa.

Tainia cordifolia is a subtropical plant with significant ornamental value. Herein, we determined the complete chloroplast (cp) genome sequence of T. cordifolia using Illumina sequencing data. The whole cp genome is 158,089 bp in size, consisting of a pair of inverted repeats (IR 25,260 bp), a large singlecopy region (LSC 86,876 bp), and a small single-copy region (SSC 20,693 bp). Plastid genome contains 136 genes, 88 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. What is more, a maximumlikelihood phylogenetic analysis demonstrated that T. cordifolia was most closely related to Oberonia japonica and Dendrobium salaccense. The cp genome will provide reference for the further investigation and research of T. cordifolia.

Cymbidium aloifolium is an epiphytic orchid with high medicinal and ornamental value. In order to get a deeper understanding of C. aloifolium , we determined the complete chloroplast genome of C. aloifolium by Illumina sequencing data. The length of this genome is 157,328 bp, including a couple of inverted repeat (IR) regions of 26,829 bp, a large single-copy (LSC) region of 85,793 bp, and a small single-copy (SSC) region of 17,877 bp. The chloroplast genome comprised of 139 genes, including 78 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. In addition, the phylogenetic analysis based on 17 chloroplast genomes of Orchidaceae indicated that C. mannii was closely related to C. aloifolium . This study will provide more valuable information for the classification and phylogenetic research of Cymbidium genus.