Abstract
Flower fragrance is one of the traits that holds important economical values in flowering plants. Extensive attention has converged on fragrance preservation in flower cultivation and breeding. Dendrobium loddigesii is an important species for cultivating aromatic Dendrobium orchid varieties for the long term due to its fragrance. Few studies focus on exploring related genes responsible for the aroma components in D. loddigesii. We analyzed flowers from two aromatic D. loddigesii varieties using high-throughput RNA sequencing and gas chromatography-mass spectrometry (GC-MS). The metabolomics results showed that the main volatile compounds responsible for the aroma formation of D. loddigesii were terpenes, especially monoterpenes. The de novo transcriptome assembly comprised 175,089 unigenes, and 24,570 unigenes of the genes were identified as differential expressed genes (DEGs) between the two varieties. Among these DEGs, 525 genes were mapped into seven pathways that related to the floral scent synthesis. Seventeen key genes were significantly correlated with volatile aroma metabolites, including geraniol, α-pinene, eugenol, and (Z)-3-hexenal. These results provide references for understanding the aroma biosynthesis and perfume formulations of D. loddigesii.
Highlights
Dendrobium loddigesii Rolfe, a perennial epiphytic herb in the Orchidaceae family [1], is a precious medicinal material in traditional Chinese medicine because of its secondary metabolites production [2,3]
Four metabolites consisted of three terpenes and one aromatics (1-ethyl-4-methoxy-benzene) that were specific to the high-scented variety (TH), while only one phenol metabolite (4-propyl-phenol) was specific to the light-scented variety (TL)
Among the differential metabolites (DMs), 27 were up-regulated and 11 were down-regulated in the TH relative to TL, the trend in the changing of DMs was consistent with the intensity of the floral scent between two aromatic D. loddigesii
Summary
Dendrobium loddigesii Rolfe, a perennial epiphytic herb in the Orchidaceae family [1], is a precious medicinal material in traditional Chinese medicine because of its secondary metabolites production [2,3]. Floral scent is one of the most significant traits that constitute the ornamental value of flowering plants [5,6]. Due to the complexities in the composition, structure, and biosynthesis process of floral scent, research findings are insufficient compared to other important ornamental characteristics such as flower shape and color [7,8]. The selection of aromatic varieties has become one of the most urgent needs, and important trends in the breeding of Dendrobium, in which the role of D. loddigesii cannot be ignored
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