Orchids constitute approximately 10% of flowering plant species. However, only about 10 orchid genomes have been published. Metabolites are the main way through which orchids respond to their environment. Dendrobium nobile, belonging to Dendrobium, the second largest genus in Orchidaceae, has high ornamental, medicinal, and ecological value. D. nobile is the source of many popular horticultural varieties. Among the Dendrobium species, D. nobile has the highest amount of dendrobine, which is regarded as one of the criteria for evaluating medicinal quality. Due to lack of data and analysis at the genomic level, the biosynthesis pathways of dendrobine and other related medicinal ingredients in D. nobile are unknown. In this paper, we report a chromosome-scale reference genome of D. nobile to facilitate the investigation of its genomic characteristics for comparison with other Dendrobium species. The assembled genome size of D. nobile was 1.19 Gb. Of the sequences, 99.45% were anchored to 19 chromosomes. Furthermore, we identified differences in gene number and gene expression patterns compared with two other Dendrobium species by integrating whole-genome sequencing and transcriptomic analysis [e.g., genes in the polysaccharide biosynthesis pathway and upstream of the alkaloid (dendrobine) biosynthesis pathway]. Differences in the TPS and CYP450 gene families were also found among orchid species. All the above differences might contribute to the species-specific medicinal ingredient biosynthesis pathways. The metabolic pathway-related analysis will provide further insight into orchid responses to the environment. Additionally, the reference genome will provide important insights for further molecular elucidation of the medicinal active ingredients of Dendrobium and enhance the understanding of orchid evolution.

Self-incompatibility affects not only the formation of seeds, but also the evolution of species diversity. A robust understanding of the molecular mechanisms of self-incompatibility is essential for breeding efforts, as well as conservation biology research. In recent years, phenotypic and multiple omics studies have revealed that self-incompatibility in Orchidaceae is mainly concentrated in the subfamily Epidendroideae, and the self-incompatibility phenotypes are diverse, even in the same genus, and hormones (auxin and ethylene), and new male and female determinants might be involved in SI response. This work provides a good foundation for future studies of the evolution and molecular mechanisms of self-incompatibility. We review recent research progress on self-incompatibility in orchids at the morphological, physiological, and molecular levels, provide a general overview of self-incompatibility in orchids, and propose future research directions.

As one of the largest families of transcription factors (TFs) in plants, the WRKY TF family plays a key role in regulating plant responses to various biotic and abiotic stresses. However, there is no confirmed method to quickly identify stress-responsive members from the WRKY gene family. In this study, all reported functional WRKY genes were first analyzed, and the amino acid patterns in response to stress were identified in group II-c (T-R/K-S/T-E/Q/D-V/I/L-E/D-I/V/H/N-L/M-D/E-D-G/E-F/Y-K/R-WRKYG-Q/K-K-A/T-VKN-S/N-P), group II-d (VPA-I/V-S-X-K-M/L/V/I-ADIP-P/A/V-D-D/E-Y/F-S-WRKYGQKPIKGSP-H/Y-PRGYYKCS-S/T-V/M-RGCPARKVER), and group II-e (PSD-S/A/L-WAWRKYGQKPIKGSPYPR-G/S-YYRCSSSKGC). WRKY genes in Dendrobium catenatum were used to validate the accuracy of these patterns. A total of 63 DcaWRKY genes were identified, their gene structures, conserved motifs, and gene expression patterns were analyzed, and a phylogenetic tree was constructed. Gene expression patterns were then analyzed under drought stress, and seven DcaWRKY genes (Dca002550, Dca002715, Dca005648, Dca007842, Dca010430, Dca016437, and Dca006787) were randomly selected to determine their expression levels and verify their expression patterns by quantitative real-time polymerase chain reaction analysis. The identified amino acid patterns were validated by drought-responsive WRKY genes in D. catenatum, confirming the accuracy of these amino acid patterns and providing valuable insights into further research of the WRKY family in D. catenatum.

Dendrobium officinale Kimura et Migo is an orchid with both medicinal and edible values and a high economic value. The wild resources of D. officinale are in an endangered state. Compared with the wild D. officinale, cultivated D. officinale exhibits inferior quality and a low content of medicinal components. Polyploid induction is a conventional breeding tool for genome doubling of species, which can effectively increase the total amount of plant components to improve the medicinal efficacy of D. officinale. In this study, D. officinale tetraploids were generated by treating the protocorms with colchicine. Morphological observations showed that tetraploids exhibited decreased plant size and leaf shape index and increased stem diameter. Cytological observations showed that the polyploid plants had larger stomata and a lower number of stomata per unit area compared with normal plants. The highest stomata variation of 30.00% was observed when the plant was treated with 0.3% colchicine for 24 h. Chromosomal observations showed that treatment of plants with 0.2% colchicine for 48 h resulted in the highest tetraploid induction rate of 10.00%. A total of 10 tetraploids were successfully obtained by inducing plant protoplasts with colchicine. The number of diploid D. officinale chromosomes was 38 with a base number of 19, and the karyotype formula was 2n = 2x = 38 = 24m + 14sm with a karyotype asymmetry coefficient of 60.59%, belonging to type 2B. The number of tetraploid D. officinale chromosomes was 76 with a base number of 19, and the karyotype formula was 2n = 4x = 76 = 58m + 18sm with a karyotype asymmetry coefficient of 60.04%, belonging to type 2B. This study determined the optimal mutagenesis treatment based on the chromosome observation results, investigated the relationship between the phenotype and ploidy level, and generated the polyploid germplasm of D. officinale, thereby laying the foundation for the breeding of new D. officinale cultivars enriched with compounds of medicinal value.

Cinnamomum camphora (L.) Presl essential oil (CCEO) is a volatile oil with aroma and is extracted from various tissues of Cinnamomumcamphora. It is traditionally used as a spice, preservative, as an anti-inflammatory and for sterilization. Terpenoids are the main active components in CCEO. Based on currently available research, considerable effort is still needed to study the biosynthesis and regulation of terpenoids in CCEO. In this review, the research progress related to terpenoid biosynthesis and bioactivity in CCEO in recent years is summarized, with the data compiled and presented mainly from online resources such as PubMed, Scopus and CNKI in China up to May 2022. The research advances related to key enzymes in the terpenoid biosynthesis pathway are mainly discussed. Previous studies have isolated some genes encoding key enzymes involved in terpenoid biosynthesis; however, among these genes, only a few TPS genes have been verified to catalyze the production of terpenoid synthases at the protein level. Most genes encoding key enzymes have been cloned and isolated, but no transgenic experiments have been carried out to verify gene function. In-depth study of the biosynthesis of terpenoids in CCEO may contribute to a better understanding of the differential accumulation of terpenoids in different types of C. camphora and provide reference for improving terpenoid content in CCEO.