Oxidosqualene cyclases in triterpenoids biosynthesis: a review / 生物工程学报

Triterpenoids are one of the most diverse compounds in plant metabolites, and they have a wide variety of physiological activities and are of important economic value. Oxidosqualene cyclases catalyze the cyclization of 2, 3-oxidosqualene to generate different types of sterols and plant triterpenoids, which is of great significance to the structural diversity of natural products. However, the mechanism of the diversified cyclization of 2, 3-oxidosqualene catalyzed by oxidosqualene cyclases remains unclear. This review summarized the research progress of oxidosqualene cyclases from the aspects of catalytic function, molecular evolutionary relationship between genes and proteins, protein structure, molecular simulation and molecular calculations, which may provide a reference for protein engineering and metabolic engineering of triterpene cyclase.

Construction of yeast one-hybrid library and screening of transcription factors regulating LS expression in Ganoderma lucidum / 中国中药杂志

Lanosterol synthase( LS) is a key enzyme involving in the mevalonate pathway( MVA pathway) to produce lanosterol,which is a precursor of ganoderma triterpenoid. And the transcriptional regulation of LS gene directly affects the content of triterpenes in Ganoderma lucidum. In order to study the transcriptional regulation mechanism of LS gene,yeast one-hybrid technique was used to screen the transcription regulators which interact withthe promoter of LS. The bait vector was constructed by LS promoter,then the vector was transformed yeast cells to construct bait yeast strain. One-hybrid c DNA library was constructed via SMART technology. Then the c DNA and p GADT7-Rec vector were co-transformed into the bait yeast strain to screen the upstream regulatory factors of the promoter region of LS by homologous recombination. Total of 23 positive clones were screened. After sequencing,blast was performed against the whole-genome sequence of G. lucidum. As a result,8 regulatory factors were screened out including the transcription initiation TFIIB,the alpha/beta hydrolase super family,ALDH-SF superfamily,60 S ribosomal protein L21,ATP synthase β-subunit,microtubule associated protein Cript,prote asome subunit β-1,and transaldolase. Until now,the regulation effect of these 8 regulatory factors in G.lucidum has not been reported. This study provides candidate proteins for in-depth study on the expression regulation of LS.

Ethylene treatment improves diosgenin accumulation in in vitro cultures of Dioscorea zingiberensis via up-regulation of CAS and HMGR gene expression

Background: The perennial medicinal herb Dioscorea zingiberensis is a very important plant used for steroid drug manufacturing for its high level of diosgenin in rhizome. Although the stimulation of diosgenin accumulation by ethylene has been reported in a few of plant species, its regulation is not yet characterized at the molecular level, the underlying molecular mechanism remains elusive. Results: In this study, the effects of ethylene on diosgenin biosynthesis in in vitro cultures of D. zingiberensis were described. The results showed that, in samples treated with ethylene at concentration E3 (10(4) dilution of 40% ethephon), the diosgenin biosynthesis was significantly promoted in comparison with the control samples. Treatment with high concentrations of ethylene had inhibitory effect, whereas with low concentration of the gas elicitor brought about no detectable deleterious effect on the growth rate and diosgenin content of the cultures. The considerable increase of diosgenin level in in vitro cultured Dioscorea zingiberensis by ethylene application is accompanied by the concomitant increase of soluble proteins and chlorophyll content. The gene expressions of cycloartenol synthase and 3-hydroxy-3-methylglutaryl-CoA reductase but not of squalene synthase or farnesyl pyrophosphate synthase were up-regulated by applied ethylene. Conclusions: Our results suggest that ethylene treatment enhanced diosgenin accumulation via up-regulation of the gene expressions of cycloartenol synthase and 3-hydroxy-3-methylglutaryl-CoA reductase.