Genome-wide identification and characterization of active ingredients related ß-Glucosidases in Dendrobium catenatum.

BACKGROUND: Dendrobium catenatum/D. officinale (here after D. catenatum), a well-known economically important traditional medicinal herb, produces a variety of bioactive metabolites including polysaccharides, alkaloids, and flavonoids with excellent pharmacological and clinical values. Although many genes associated with the biosynthesis of medicinal components have been cloned and characterized, the biosynthetic pathway, especially the downstream and regulatory pathway of major medicinal components in the herb, is far from clear. ß-glucosidases (BGLUs) comprise a diverse group of enzymes that widely exist in plants and play essential functions in cell wall modification, defense response, phytohormone signaling, secondary metabolism, herbivore resistance, and scent release by hydrolyzing ß-D-glycosidic bond from a carbohydrate moiety. The recent release of the chromosome-level reference genome of D. catenatum enables the characterization of gene families. Although the genome-wide analysis of the BGLU gene family has been successfully conducted in various plants, no systematic analysis is available for the D. catenatum. We previously isolated DcBGLU2 in the BGLU family as a key regulator for polysaccharide biosynthesis in D. catenatum. Yet, the exact number of DcBGLUs in the D. catenatum genome and their possible roles in bioactive compound production deserve more attention. RESULTS: To investigate the role of BGLUs in active metabolites production, 22 BGLUs (DcBGLU1-22) of the glycoside hydrolase family 1 (GH1) were identified from D. catenatum genome. Protein prediction showed that most of the DcBGLUs were acidic and phylogenetic analysis classified the family into four distinct clusters. The sequence alignments revealed several conserved motifs among the DcBGLU proteins and analyses of the putative signal peptides and N-glycosylation site revealed that the majority of DcBGLU members dually targeted to the vacuole and/or chloroplast. Organ-specific expression profiles and specific responses to MeJA and MF23 were also determined. Furthermore, four DcBGLUs were selected to test their involvement in metabolism regulation. Overexpression of DcBGLU2, 6, 8, and 13 significantly increased contents of flavonoid, reducing-polysaccharide, alkaloid and soluble-polysaccharide, respectively. CONCLUSION: The genome-wide systematic analysis identified candidate DcBGLU genes with possible roles in medicinal metabolites production and laid a theoretical foundation for further functional characterization and molecular breeding of D. catenatum.

Gigantol inhibits Wnt/ß-catenin signaling and exhibits anticancer activity in breast cancer cells.

BACKGROUND: Gigantol is a bibenzyl compound derived from several medicinal orchids. This biologically active compound has been shown to have promising therapeutic potential against cancer cells, but its mechanism of action remains unclear. METHODS: The inhibitory effect of gigantol on Wnt/ß-catenin signaling was evaluated with the SuperTOPFlash reporter system. The levels of phosphorylated low-density lipoprotein receptor related protein 6 (LRP6), total LRP6 and cytosolic ß-catenin were determined by Western blot analysis. The expression of Wnt target genes was analyzed using real-time PCR. Cell viability was measured with a MTT assay. The effect of gigantol on cell migration was examined using scratch wound-healing and transwell migration assays. RESULTS: Gigantol decreased the level of phosphorylated LRP6 and cytosolic ß-catenin in HEK293 cells. In breast cancer MDA-MB-231 and MDA-MB-468 cells, treatment with gigantol reduced the level of phosphorylated LRP6, total LRP6 and cytosolic ß-catenin in a dose-dependent manner, resulting in a decrease in the expression of Wnt target genes Axin2 and Survivin. We further demonstrated that gigantol suppressed the viability and migratory capacity of breast cancer cells. CONCLUSION: Gigantol is a novel inhibitor of the Wnt/ß-catenin pathway. It inhibits Wnt/ß-catenin signaling through downregulation of phosphorylated LRP6 and cytosolic ß-catenin in breast cancer cells.

[DNA barcoding identification of endangered medicinal plants of Orchidaceae].

In this study, DNA barcoding was used to validate the traditional morphological classification of medicinal plants of Orchidaceae. The 163 samples of 135 species belong to 49 genera which have been confirmed by morphological identification were collected. Candidate sequences, including matK, psbA-trnH and ITS2 sequences, were amplified, bidirectionally sequenced, and assembled. All the sequences were blasted to GenBank database at NCBI, then analyzed using Neighbor-joining tree method by MEGA 7.0. The results showed that the DNAs of 163 samples were successfully extracted. The amplification efficiency of matK, psbA-trnH and ITS2 sequences were 100%, 100% and 98.77%, respectively. The 487 sequences were obtained, 345 sequences of which have matched corresponding sequences in the GenBank database and 142 sequences were new sequences. The topology of NJ tree which were constructed with the matK sequences was better than the trees of psbA-trnH and ITS2 sequences. In conclusion, the matK, psbA-trnH and ITS2 sequences were complementary and suitable for identification of medicinal plants of Orchidaceae. DNA barcoding can be used as an auxiliary means for identification of medicinal plants of Orchidaceae.

Comparison of hypoglycemic and antioxidative effects of polysaccharides from four different Dendrobium species.

Four polysaccharides from Dendrobium huoshanense (DHP), D. officinale (DOP), D. nobile (DNP) and D. chrysotoxum (DCP), which had obvious differences in intrinsic viscosities and monosaccharide compositions, were extracted to compare their hypoglycemic and antioxidative activities in alloxan-induced diabetic mice by oral administration. The analysis of fasting blood glucose, glycosylated serum protein and serum insulin levels showed that DHP, DOP and DNP, but not DCP, possessed significant hypoglycemic effect with the decreasing order of DHP>DNP>DOP. Histopathological observation confirmed the capability of DHP, DOP and DNP to intervene the damage in pancreas tissues. The determination of superoxide dismutase, catalase, malonaldehyde and L-glutathione levels in the liver and kidney displayed that DHP, DOP and DNP had protective effects against alloxan-induced oxidative damage and the effect of DHP ranked first. These results suggested that there were significant differences in hypoglycemic and antioxidative activities between four Dendrobium polysaccharides, which may be contributed to their physicochemical properties.

[A study on chilling injury in medicinal plants region of South China Botanical Garden].

From late January to early February in 2008, Guangzhou suffered from the cold and humid rainy for 20 days, and the daily mean temperature was under 10 degrees C. In 794 species of medicinal plants in South China Botanical Garden, 78 species (9.8%) suffered from chilling injury. The reasons were analyzed and some useful suggestions were made.