Effect and Mechanism of Arbuscular Mycorrhizal Fungi in Herbs / 中国实验方剂学杂志

Arbuscular mycorrhizal fungi （AMF） can establish mycorrhizal symbiosis system with most terrestrial plants，and play important roles in their growth and development. However，there is no systematic analysis and summarization of their roles in the growth, biosynthesis and accumulation of active substances of herbs，as well as stress-resistance mechanism. First，the main research methods of AMF were summarized in the paper，including the separation of AMF spores，morphological identification，chemical staining and molecular identification. The main morphological structures of some AMF were detailed in the table. In terms of growth promotion，AMF promoted the growth by prolonging mycelium，enhancing phosphatase secretion，organic acid，activation of soil and increasing absorption efficiency. In the aspect of biosynthesis and accumulation of flavonoids，terpenoids and other active substances in herbs，AMF improved the contents by regulating activities of signal substances and key enzymes involved in the metabolism of secondary products. In addition，AMF could alleviate a series of stresses caused by drought，heavy metal，high salt，high or low temperature by improving the activity of antioxidant enzymes，enhancing the ability of plants to scavenge free radicals，complexing toxic heavy metals，diluting high salt concentration，or inducing the expressions of key genes. Finally，the application prospects and in-depth study of AMF in the ecological planting of herbs were discussed, in order to provide reference for promoting relevant research.

Biosynthesis of Steroidal Saponins in Herbs / 中国实验方剂学杂志

Steroidal saponins are efficacious substances wildly existed in the herbs，and consist of glycosyl and steroid sapogenin. The biosynthesis pathways of steroidal saponins mainly include the cytosolic mevalonate （MVA） pathway and the plastidial methylerythritol 4-phosphate （MEP） pathway，with the MVA pathway as the main pathway. The key enzymes are involved in the biosynthetic pathway, including 3-hydroxy-3-methyl glutaryl coenzyme A reductase（HMGR），1-deoxy-D-xylulose 5-phosphate synthase（DXS），1-deoxy-D-xylulose-5-phosphatereduetoisomerase（DXR），farnesyl pyrophosphate synthase（FPS），squalene synthase（SS），squalene epoxidase（SE），cycloartenol synthase（CAS），cytochrome P450（CYP450），and steroidalglycosyltransferase（SGTase）. In the paper，the biosynthesis roadmap of steroidal saponins was optimized based on previous studies. According to a comprehensive analysis on studies of key enzymes for the past five years, genes, like HMGR，SS，CYP450 and UGT，were studied more，while other genes，like FPS，SE，CAS，were known less. In conclusion， current studies still focus on the primary stage，but lack direct evidence for the roles of key enzymes. This paper would provide a reference and theoretical support for subsequent studies.

Phosphate-solubilizing function evaluation and taxonomic identification of endophytic fungi separated from roots of Amomum villosum / 中草药

Objective: To study the characteristics of endophytic fungi separated from the roots of Amomum villosum grown in Jinping County of Yunnan Province, including the culture, evaluation of phosphorus-solubilizing ability and taxonomic identification of target strains. Methods: Endophytic fungi in the roots of A. villosum were separated by culturing in the mediums of PDA and MEA, and purely cultured in PDA. The endophytic fungi with phosphorus-solubilizing ability were screened by solid and liquid mediums of Pikovaskaia’s (PVK) prepared with inorganic phosphorus source. Then, the phosphorus-solubilizing capacity and reasonable mechanism were analyzed by growth circle, biomass, effective phosphorus content, pH value, and phosphatase activity. Moreover, molecular identification of target strains with the capacity of phosphorus-solubilizing would be carried out by ribosome 18 S PCR amplification. Results: The results showed that 24 endophytic fungi were separated from the roots of A. villosum in total, 10 of which were dark septate endophytes (DSE). Eight strains could grow on PVK solid medium and produce phosporus-dissolved growth circle. The growth circle diameters of JP-20 and JP-23 were larger than others, and more than 9 cm, followed by JP-15 with the growth circle of 6.06 cm. Furthermore, it was shown that JP-23 had a strong ability of phosphate-solubilizing due to presenting a high biomass in the PVK liquid medium instead of the medium prepared by soluble phosphorus source. The content of effective phosphorus of JP-23 in PVK liquid medium was significantly increased with an obviously decreasing pH and a sharply rising of acid phosphatase (ACP) activity. Moreover, the strain JP-23 was preliminarily identified as Cladosporium sp. (GenBank: MK629004) by molecular identification. Conclusion: An assumption was concluded that strain JP-23 could decompose and use insoluble phosphorus sources by adjusting the pH value and secreting ACP in medium. Our findings would provide data support and theoretical basis for studying the phosphate absorption mechanism of plant-microbial symbiosis system and the ecological plantation of A. villosum.

Colonization investigation of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in roots of Polygonatum kingianum and their correlations with content of main functional components in rhizomes / 中草药

Objective: To investigate the colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in the roots of Polygonatum kingianum planted at different areas, and explore the correlations between the colonization rate and the main functional components. Methods: Fresh roots of P. kingianum from five plots in Yunnan Province were taken as research objects. The alkali dissociation method was used to investigate the colonization of AMF and DSE in the roots of P. kingianum. Then the morphological structure was photographed. The content of P. sibiricum polysaccharides, diosgenin, total flavonoids and extractum were separately determined by phonel-sulfate method, colorimetry method of vanillin-acetic acid-perchloric acid, spectrophotometry method with rutin standard and hot dipping method with alcohol. The correlations between the colonization rates of AMF or DSE and four main functional components were analyzed by Pearson correlation coefficient method. Results: The average colonization of AMF and DSE in the five plots were 26.25%-57.54% and 31.67%-45.19%, respectively. The colonization rates of AMF and DSE from HHMZ was higher than the other four others. All of correlations among the colonization rates of AMF, DSE and their typical structure and the four main functional components in the rhizomes were positive correlation, in which the correlations between the content of polysaccharides, diosgenin or total flavonoids and the colonization rates of AMF or DSE were higher, and their correlation coefficient were respectively 0.838/0.887, 0.819/0.703, and 0.785/0.855 (AMF/DSE). Furthermore, the correlations between the content of polysaccharides and the colonization rates of AMF hypha or DSE were significant. In addition, there were high correlations among the colonization rates of AMF, DSE and their typical structures, as well as the content in pairs of four functional components. Conclusion: There were higher colonization rates of AMF and DSE in the fibrous roots of P. kingianum. The correlations between the colonization rates of AMF or DSE and each main functional component were positive. This study provides data support and experimental basis for the implementation of ecological planting of P. kingianum and the use of biological means to increase production and income.rates