Regulation Of Jasmonic Acid And Other Chemical Factors On Gynostemma Pentaphyllum Gypenosides Biosynthesis

Jiaogulan[Gynostemma pentaphyllum?Thunb.?Makino]is an important medicinal plant in Gynostemma BL.,Cucurbitaceae.It is known as“ginseng in the South”because of its ability to synthesize and accumulate ginsenosides.Jasmonic acid is a key signal molecule that regulates plant growth and secondary metabolism,and accelerates the development and ginsenosides accumulation in Panax species.Hypothetically,jasmonates could enhance the biosynthesis of gypenosides via regulating the gene expression of key enzymes in G.pentaphyllum.In this thesis,the effect of jasmonates as well as the chemical factors on the gene expression of key enzymes in gypenoside biosythesis in G.pentaphyllum seedlings,and the correlation between the gene expression and the contents of total gypenosides and monomers were proposed by means of phytochemistry and molecular biology,to elucidate the biosynthesis mechanism of jasmonates regulating gypenosides.The main results were as follows:1.The acidity and basicity of water saturated n-butanol,an extraction solvent of gypenoside,affected the extraction yield of total gypenosides in the processing of extracting gypenosides.The highest yield of total gypenosides was got at the pH of 8,which was 223.57%of the general extraction pH of 5.2.The gene expression models of the key enzymes in gypenoside biosythesis were inconformity during 2 h to 3 d stages after spraying MeJA of 0.5?M on mature leaves of G.pentaphyllum.The change trend of gene expression of GpFPS was decreased firstly and increased lately,which was similar to that of GpSS,while the trend of GpSS was opposed.The content of total gypenosides increased at different degrees after the treatment of MeJA,and also exhibited a trend of descend in first and ascend at last.3.A correlation analysis was conducted between the gene expression of the key enzymes during 2 h to 3 d and the content of total gypenosides determined during 6 h to6 d after the MeJA treatment.Significant positive correlation was established between the expression of GpFPS and the content of total gypenosides,and positive correlation without significant was also existed between that of GpSS and the gypenosides,which suggested these two genes promoted the biosynthesis of gypenosides.On the contrary,the gene expression of GpSE showed a negative correlation to the content of toatal gypenosides,indicating its inhibited effect on the saponin biosynthesis.Gypenoside monomers Rb₁ and Rb₃ were found to have significant positive correlation with GpFPS,and monomer Rd also had a non-significant positive correlation with GpFPS,which meant this gene was favorable to the biosynthesis of gypenoside monomers.4.Up-regulation of the gene expression of GpFPS?GpSE?GpSS were observed in the fibrous roots after spraying linolenic acid of 0.5?M on G.pentaphyllum.The expression levels of the genes in roots not only higher than the controls,but also higher those existed in stems and young leaves.The available data did not support the fact that LeA could strongly regulate the gene expression and thus synthesized gypenosides.5.The inconformity of the three gene expression models were showed when coronatine of 20?M was emploied to spray on G.pentaphyllum.The expression levels of GpFPS and GpSE were higher than that of GpSS in the roots,stems and young leaves.The regulation of COR on the genes of key enzymes was not significant and it was disadvantage in promoting the saponin biosynthesis in mature leaves.6.The gene expression exhibited different ways in the vegetative organs after spraying 0.5%of ethephon on the plant.ET down-regulated the key enzyme gene expression shortly after the treatment,revealed its possible function of inhibiting the biosynthesis of gypenoside monomers.7.Similar gene expression models were found in stems after the treatment of 0.1%H₂O₂ on the plant.All of the genes had the highest expression level in roots and the least level in young leaves.The weak regulation of H₂O₂ on gene expression in mature leaves led to less biosynthesis of gypenoside.8.Down-regulated gene expressions of GpFPS?GpSE?GpSS were formed at the initial stage of GSAP?gravitropism of shoot apex propagation,a special phenomenon of vegetative propagation,that is before withering of its vine at the end of autumn,the internodes of apical buds become shortly and largely,and then grow downward and enter into the soil,where each of them develops into several axillary buds through the winter.New shoots arise from the underground buds in the next spring?.No correlation could be established between the gene expression and the contents of total gynostemma or saponin monoers.