Apocynum plants, especially A. venetum and A. hendersonii, are rich in flavonoids. In the present study, a whole genome survey of the two species was initially carried out to optimize the flavonoid biosynthesis-correlated gene mining. Then, the metabolome and transcriptome analyses were combined to elucidate the flavonoid biosynthesis pathways. Both species have small genome sizes of 232.80 Mb (A. venetum) and 233.74 Mb (A. hendersonii) and showed similar metabolite profiles with flavonols being the main differentiated flavonoids between the two specie. Positive correlation of gene expression levels (flavonone-3 hydroxylase, anthocyanidin reductase, and flavonoid 3-O-glucosyltransferase) and total flavonoid content were observed. The contents of quercitrin, hyperoside, and total anthocyanin in A. venetum were found to be much higher than in A. hendersonii, and such was thought to be the reason for the morphological difference in color of A. venetum and A. hendersonii. This study provides valuable genomic and metabolome information for understanding of A. venetum and A. hendersonii, and lays a foundation for elucidating Apocynum genus plant flavonoid biosynthesis.

Background The bast fiber crop ramie can be used as high-quality forage resources, especially in tropical or subtropical region where there is lack of high-quality protein feed. Hongxuan No.1 (HX_1) is a unique ramie variety with a light reddish brown leaf color, which is obviously different from elite cultivar, Zhongzhu No.1 (ZZ_1, green leaf). While, the regulatory mechanism of color difference or secondary metaboliates synthesis between these two varieties have not been studied. Results In this study, phenotypic, transcriptomic and metabolomic analysis of HX_1 and ZZ_1 were conducted to elucidate the mechanism of leaf color formation. Chromaticity value and pigment content measuring showed that anthocyanin was the main metabolites imparting the different leaf color phenotype between the two varieties. Based on LC/MS, at least 14 anthocyanins were identified in leaves of HX_1 and ZZ_1, and the HX_1 showed the higher relative content of malvidin-, pelargonidin-,and cyanidin-based anthocyanins. Transcriptome and metabolome co-analysis revealed that the up-regulated expression of flavonoids synthesis gene was positively correlated with total anthocyanins accumulation in ramie leaf, and the differentfially expression of “blue gene” (F3’5’H) and the “red gene” (F3’H) in leaves bring out HX_1 metabolic flow more input into the cyanidin branch. Furthermore, the enrichment of glycosylated modification pathway (UGT and AT) and the expression of flavonoid 3-O-glucosyl transferase (UFGT), anthocyanidin reductase (ANR), in leaves were significantly influenced the diversity of anthocyanins between HX_1 and ZZ_1. Conclusions Phenotypic, transcriptomic and metabolomic analysis of HX_1 and ZZ_1 indicated that the expression levels of genes related to anthocyanin metabolism contribute to the color formation of ramie variety. Anthocyanins are important plant secandary metabilates with many physiological functions, the results of this study will deepened our understanding of ramie leaf color formation, and provided basis for molecular breeding of functional forage ramie.

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The study is aimed at establishing a simple protocol for in vitro regeneration of sweet potato with a view to providing planting materials to farmers as well as basis for genetic improvement. Axillary buds were excised and cultured on Murashige and Skoog (MS) basal salts supplemented with 6-benzyl aminopurine (BAP), gibberellic acid (GA 3 ) and naphthalene acetic acid (NAA) singly or in combination. The shoot height and number of leaves differed significantly among the cultivars. The result also indicated significant difference (p< 0.01) among the cultivars with King J recording the highest mean values. Significant differences (p< 0.05) was also recorded in the media combination with respect to organogenesis and number of shoots obtained. The results of hardening further revealed 33.33% success in the explants transferred directly to the field, as well as for the plantlets that were gradually weaned in a mixture of 3:1 sand and biochar.

Apocynum hendersonii is a traditional medicinal plant used primarily as tea. It has a potential health benefit from its rich bioactive substances. This study investigated the reactivity of solvents of different polarities (ethanol, ethyl acetate, n-hexane, methanol, and water) extracts of the A. hendersonii leaf. The phytochemical composition of the extracts was evaluated using a Fourier Transform Infrared spectrophotometer (FT-IR), Gas Chromatography-Mass Spectrometry (GC-MS), UHPLC-MS, and Higher Performance Liquid Chromatography (HPLC). The result revealed the presence of medicinally important bioactive constituents, including phenols, flavonoids, and polysaccharides. Methanol extracts exhibited the highest flavonoid contents (20.11 ± 0.85 mg QE/g DW) and the second-highest in terms of phenolic (9.25 ± 0.03 mg GAE/g DW) and polysaccharide (119.66 ± 2.65 mg GE/g DW). It also had the highest antioxidant capacity with 60.30 ± 0.52% and 4.60 ± 0.02 µmol Fe2+ per g DW based on a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and ferric reducing antioxidant power (FRAP), respectively. Ethanol extract displayed the maximum antibacterial action against Gram-negative and Gram-positive bacteria and the highest inhibition activity against the enzymes tyrosinase and acetylcholinesterase, followed by methanol extract. The principal component analysis revealed a positive correlation between the constituents, bioactivities, and extracts. The overall result showed A. hendersonii as a rich natural source of antimicrobial and antioxidant bioactive compounds and may be used for future applications in pharmaceuticals and food industries.

Sterilization procedure, media composition, explants selection and control of physical environment are critical for successful cultures and callus induction with surface sterilization being very challenging in most plants. Five different sterilization methods were evaluated to come up with the best for subsequent use to establish an in vitro regeneration method for the induction of callus in Curcuma caesia using excised leaf and rhizome explants. Murashige and Skoog (MS) media supplemented with various concentration of 2,4-Dichlorophenoxy acetic acid (2,4-D)/Indole-3-acetic acid (IAA) (0.5- 5.0mg/L), singly or in combination with Benzyl aminopurine (BAP)/Kinetin (KIN) (0.1-5.0mg/L), 0.3% sucrose and 0.08% agar were used. The result of the sterilization procedures showed 15% NaHClO3 (5min) + 70% Ethanol (30s) + 0.1% HgCl2 (5min) to be the most effective in controlling contamination in C. caesia among all the treatments tested. The response to callus induction was found to depend on the type of explants used and growth regulators combination. Leaf explants gave the highest percentage of callus induction. Highest percentage of callus induction (66.70%) was obtained in the growth regulator combination of 2, 4-D (0.5mg/L) + BAP (0.1mg/L) and least (14.29%) in IAA (2.0mg/L) + BAP (0.5mg/L). Equal and higher concentration of 2, 4-D + BAP of 5.0mg/L each also provided better result (40.00%). No callus was obtained in all the single concentration of 2, 4-D used.

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Ramie ( Boehmeria nivea ) is a perennial herb that is highly tolerant of heavy metals. In the present study, we cloned a novel metallothionein‐like gene from ramie; this gene, termed Bn MTL , encodes a putative 46 amino acid protein with a molecular mass of 4.38 kD a. Analysis using quantitative RT ‐ PCR revealed that cadmium (Cd 2+ ) treatment results in elevated expression of Bn MTL in the roots. We heterologously overexpressed Bn MTL in Escherichia coli cells to examine its binding to Cd 2+ and its possible role in homeostasis. Recombinant E. coli cells expressing Bn MTL exhibited a high tolerance of Cd 2+ stress up to a concentration of 1 m m , and the observed accumulation of Cd 2+ was almost eight‐fold higher than the control. These results demonstrate that Bn MTL (i) is highly expressed in the root following exposure to Cd 2+ and (ii) encodes a typical metallothionein‐like protein with high cadmium‐binding activity.