Fraxinus hupehensis is an endangered tree species that is endemic to in China; the species has very high commercial value because of its intricate shape and potential to improve and protect the environment. Its seeds show very low germination rates in natural conditions. Preliminary experiments indicated that gibberellin (GA3) effectively stimulated the seed germination of F. hupehensis. However, little is known about the physiological and molecular mechanisms underlying the effect of GA3 on F. hupehensis seed germination. We compared dormant seeds (CK group) and germinated seeds after treatment with water (W group) and GA3 (G group) in terms of seed vigor and several other physiological indicators related to germination, hormone content, and transcriptomics. Results showed that GA3 treatment increases seed vigor, energy requirements, and trans-Zetain (ZT) and GA3 contents but decreases sugar and abscisic acid (ABA) contents. A total of 116,932 unigenes were obtained from F. hupehensis transcriptome. RNA-seq analysis identified 31,856, 33,188 and 2056 differentially expressed genes (DEGs) between the W and CK groups, the G and CK groups, and the G and W groups, respectively. Up-regulation of eight selected DEGs of the glycolytic pathway accelerated the oxidative decomposition of sugar to release energy for germination. Up-regulated genes involved in ZT (two genes) and GA3 (one gene) biosynthesis, ABA degradation pathway (one gene), and ABA signal transduction (two genes) may contribute to seed germination. Two down-regulated genes associated with GA3 signal transduction were also observed in the G group. GA3-regulated genes may alter hormone levels to facilitate germination. Candidate transcription factors played important roles in GA3-promoted F. hupehensis seed germination, and Quantitative Real-time PCR (qRT-PCR) analysis verified the expression patterns of these genes. Exogenous GA3 increased the germination rate, vigor, and water absorption rate of F. hupehensis seeds. Our results provide novel insights into the transcriptional regulation mechanism of effect of exogenous GA3 on F. hupehensis seed germination. The transcriptome data generated in this study may be used for further molecular research on this unique species.

3-Hydroxy-3-methylglutaryl-CoA synthase (HMGS) is one of the rate-limiting enzymes in the mevalonate pathway as it catalyzes the condensation of acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA. In this study, A HMGS gene (designated as GbHMGS1) was cloned from Ginkgo biloba for the first time. GbHMGS1 contained a 1422-bp open-reading frame encoding 474 amino acids. Comparative and bioinformatics analysis revealed that GbHMGS1 was extensively homologous to HMGSs from other plant species. Phylogenetic analysis indicated that the GbHMGS1 belonged to the plant HMGS superfamily, sharing a common evolutionary ancestor with other HMGSs, and had a further relationship with other gymnosperm species. The yeast complement assay of GbHMGS1 in HMGS-deficient Saccharomyces cerevisiae strain YSC6274 demonstrated that GbHMGS1 gene encodes a functional HMGS enzyme. The recombinant protein of GbHMGS1 was successfully expressed in E. coli. The in vitro enzyme activity assay showed that the k_cat and K_m values of GbHMGS1 were 195.4 min⁻¹ and 689 μM, respectively. GbHMGS1 was constitutively expressed in all tested tissues, including the roots, stems, leaves, female flowers, male flowers and fruits. The transcript accumulation for GbHMGS1 was highest in the leaves. Expression profiling analyses revealed that GbHMGS1 expression was induced by abiotic stresses (ultraviolet B and cold) and hormone treatments (salicylic acid, methyl jasmonate, and ethephon) in G. biloba, indicating that GbHMGS1 gene was involved in the response to environmental stresses and plant hormones.

Camellia oleifera Abel. (C. oleifera), one of the four woody oil-producing plants in the world produces edible oils with high percentage of unsaturated fatty acid content in seeds. The mature C. oleifera seeds continue to undergo a series of physiological changes after harvest. To this end, the dynamic changes in nutrients, oil content, fatty acid composition, and endogenous hormone content in C. oleifera seeds under different natural drying times after harvest were investigated. The content of soluble sugar and soluble protein of C. oleifera seeds increased with the extension of natural drying, especially soluble sugar content increased nearly 2-fold at 30 d after post-harvest natural drying compared with that of the control group. The content of oil reached a peak (23.6%) at 30 d after post-harvest natural drying. During the post-harvest natural drying process, the relative content of palmitic acid and oleic acid increased, while the relative content of palmitic acid and linoleic acid decreased. Furthermore, the levels of unsaturated fatty acids (oleic acid, linoleic acid, linolenic acid, and arachidonic acid) increased significantly with increasing natural drying time. The overall trend of endogenous hormones SA, SL, and ACC concentrations increased with the post-harvest natural drying process. Furthermore, the concentration of SA, SL, and ACC were positively correlated with oil content. Altogether, post-harvest natural drying for 30 days significantly promoted the anabolism of oil and improved the quality of C. oleifera seeds. These findings provide a scientific basis for reasonable post-harvest treatment to improve Camellia oil yield.

Matricaria recutita is a widely used medicinal plant with broad pharmacological effects, and α-bisabolol is the main active ingredient of this plant. To improve its α-bisabolol content, M. recutita was sprayed with different concentrations (1.0, 2.0,and 4.0 mmol.L−1) of 5-aminolevulinic acid (ALA) or with water as a control to study the effects of ALA treatment on the photosynthesis, antioxidant system, and α-bisabolol content of M. recutita. Results showed that the photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, soluble protein, total amino acids, soluble sugar, and α-bisabolol of M. recutita were significantly increased. Moreover, the activities of superoxide dismutase, peroxidase, and catalase of M. recutita were also enhanced by ALA treatment. Optimal results were obtained when the concentration of ALA was 2.0 mmol.L−1. Results showed that ALA treatment could improve the α-bisabolol content of M. recutita, and the underlying physiological mechanism was analyzed. ALA treatment was an effective measure for improving the medicinal value of M. recutita.

Chamaemelum nobile is a traditional Chinese herbal medicine, whose secondary metabolites used in the pharmacology of Chinese medicine. Among them, the flavonoids have great research value. Flavanone 3-hydroxylase (F3H) is one of the core enzymes in the early steps of flavonoid biosynthesis. This study aimed to elucidate the structures, functions, and expression levels of F3H families from C. nobile. Four members of the F3H family were screened from C. nobile transcriptome data and performed bioinformatics analysis. Results showed that CnF3H1~4 had a high similarity with the other F3H plants, and all genes contained two conserved isopenicillin N synthase-like and oxoglutarate/iron-dependent dioxygenase domains. Further analysis revealed that the four CnF3H proteins contained some differences in binding sites. The results of secondary and 3-D structures displayed that the composition and proportion of the four CnF3H secondary structures were basically the same, and their 3D structures were consistent with the secondary structures. The phylogenetic tree displayed that CnF3H2, CnF3H3, and CnF3H4 were grouped with Asteraceae. The expression patterns of CnF3Hs in the roots, stems, leaves, and flowers of C. nobile were evaluated using the value of RPKM. The results indicated that CnF3Hs had significant difference in the expression of different tissues. Especially, CnF3H1~3 and CnF3H4 had the highest expression levels in the flowers and roots, respectively. Hence, CnF3Hs played a significant role in the flavonoid metabolism.