Transcriptomic responses to drought stress in Polygonatum kingianum tuber.

BACKGROUND: Polygonatum kingianum Coll. et Hemsl. is an important plant in Traditional Chinese Medicine. The extracts from its tubers are rich in polysaccharides and other metabolites such as saponins. It is a well-known concept that growing medicinal plants in semi-arid (or drought stress) increases their natural compounds concentrations. This study was conducted to explore the morpho-physiological responses of P. kingianum plants and transcriptomic signatures of P. kingianum tubers exposed to mild, moderate, and severe drought and rewatering. RESULTS: The stress effects on the morpho-physiological parameters were dependent on the intensity of the drought stress. The leaf area, relative water content, chlorophyll content, and shoot fresh weight decreased whereas electrolyte leakage increased with increase in drought stress intensity. A total of 53,081 unigenes were obtained; 59% of which were annotated. We observed that 1352 and 350 core genes were differentially expressed in drought and rewatering, respectively. Drought stress driven differentially expressed genes (DEGs) were enriched in phenylpropanoid biosynthesis, flavonoid biosynthesis, starch and sucrose metabolism, and stilbenoid diarylheptanoid and gingerol biosynthesis, and carotenoid biosynthesis pathways. Pathways such as plant-pathogen interaction and galactose metabolism were differentially regulated between severe drought and rewatering. Drought reduced the expression of lignin, gingerol, and flavonoid biosynthesis related genes and rewatering recovered the tubers from stress by increasing the expression of the genes. Increased expression of carotenoid biosynthesis pathway related genes under drought suggested their important role in stress endurance. An increase in starch and sucrose biosynthesis was evident from transcriptomic changes under drought stress. Rewatering recovered the drought affected tubers as evident from the contrasting expression profiles of genes related to these pathways. P. kingianum tuber experiences an increased biosynthesis of sucrose, starch, and carotenoid under drought stress. Drought decreases the flavonoids, phenylpropanoids, gingerol, and lignin biosynthesis. These changes can be reversed by rewatering the P. kingianum plants. CONCLUSIONS: These results provide a transcriptome resource for P. kingianum and expands the knowledge on the effect of drought and rewatering on important pathways. This study also provides a large number of candidate genes that could be manipulated for drought stress tolerance and managing the polysaccharide and secondary metabolites' contents in P. kingianum.

Preparation and pharmacodynamic study of Oral Disintegration Tablets of "Hugan I" / 中草药

Objective: To optimize the prescription and preparation process of "Hugan I" Orally Disintegrating Tablets, and investigate its efficacy against acute liver injury in mice. Methods: Single factor method was used for disintegrants, lubricants, and fillers screening. Taking the appearance, hardness, friability and disintegration time of the tablets as the comprehensive evaluation index, the dosage of disintegrant, micro-silica gel and magnesium stearate was selected as the investigation factor. The Box-Behnken response surface method was used to optimize the orally disintegrating tablets. Acetaminophen (APAP, 500 mg/kg) was used to replicate acute liver injury model by one-time high-dose intragastric administration to investigate the effects of orally disintegrating tablets on the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum, the content of glutathione (GSH) and malondialdehyde (MDA) and morphological changes in liver tissue. Results: The optimal prescription was as following: dry paste powder 22.00%, microcrystalline cellulose 18.00%, sorbitol 20.00%, mannitol 16.00%, Aspartame 0.50%, citric acid 0.50%, disintegration agent L-HPC 20.00%, micro-powder silica gel 2.50% and magnesium stearate 0.50%. The hardness of the orally disintegrating tablets was 4-7 kg, the mean disintegration time was about 50 s, and the mean friability was around 0.85%. Compared with the model group, there were significant differences (P < 0.01) in Biphenyl diester control group, "Hugan I" Decoction group and "Hugan I" Orally Disintegrating Tablets group, and the levels of ALT and AST in the serum of the mice were significantly decreased, The content of MDA in the liver tissue was decreased, which improved the damage of APAP to liver tissue. Conclusion: The formulation of the "Hugan I" Orally Disintegrating Tablet is feasible and easy to operate, which achieves the same effect with "Hugan I" Decoction that effectively prevent liver damage caused by acetaminophen with no significant differences.

De novo Transcriptome Characterization of Rhodomyrtus tomentosa Leaves and Identification of Genes Involved in α/ß-Pinene and ß-Caryophyllene Biosynthesis.

Plant-derived terpenes are effective in treating chronic dysentery, rheumatism, hepatitis, and hyperlipemia. Thus, understanding the molecular basis of terpene biosynthesis in some terpene-abundant Chinese medicinal plants is of great importance. Abundant in mono- and sesqui-terpenes, Rhodomyrtus tomentosa (Ait.) Hassk, an evergreen shrub belonging to the family Myrtaceae, is widely used as a traditional Chinese medicine. In this study, (+)-α-pinene and ß-caryophyllene were detected to be the two major components in the leaves of R. tomentosa, in which (+)-α-pinene is higher in the young leaves than in the mature leaves, whereas the distribution of ß-caryophyllene is opposite. Genome-wide transcriptome analysis of leaves identified 138 unigenes potentially involved in terpenoid biosynthesis. By integrating known biosynthetic pathways for terpenoids, 7 candidate genes encoding terpene synthase (RtTPS1-7) that potentially catalyze the last step in pinene and caryophyllene biosynthesis were further characterized. Sequence alignment analysis showed that RtTPS1, RtTPS3 and RtTPS4 do not contain typical N-terminal transit peptides (62-64aa), thus probably producing multiple isomers and enantiomers by terpenoid isomerization. Further enzyme activity in vitro confirmed that RtTPS1-4 mainly produce (+)-α-pinene and (+)-ß-pinene, as well as small amounts of (-)-α-pinene and (-)-ß-pinene with GPP, while RtTPS1 and RtTPS3 are also active with FPP, producing ß-caryophyllene, along with a smaller amount of α-humulene. Our results deepen the understanding of molecular mechanisms of terpenes biosynthesis in Myrtaceae.