| Ginseng(Panax Ginseng C.A.Meyer)is one of the most medically important plants in the world,and is also the medical edible plant that was rich in nutrition.Ginsenosides are the major bioactive ingredient in ginseng,which are the marker compounds to evaluate the quality of ginseng drugs and foods.The pharmacological effects of ginsenosides including anti-aging,anti-inflammatory,anti-cancer,adjust blood pressure,inhibit the growth of HIV and pain relief.Dammarane-type ginsenosides constitute more than 80%of the total ginsenosides,which mainly include protopanaxatriol-type(PPT-type)and protopanaxadiol-type(PPD-type)ginsenosides.However,ginsenoside contents is little that account for about 4%of the dry weight in ginseng,and the accumulation mechanism is not clear at present.Thus,this study uses ginseng cells as materials to study the effects of chilling on ginsenoside accumulation in ginseng cells,and provides theory basis for ginsenoside accumulation.The results of this study showed that continuous chilling(5℃ for 12 h)induced the PPT-type ginsenosides;in contrast,intermittent chilling(25℃ for 12 h and 5℃for 12 h)stimulated the accumulation of PPD-type ginsenosides,which indicated that different chilling treatments stimulated the accumulation of different types of ginsenosides.Then,the transcriptional expression of 19 gene individuals of 13 enzyme genes or gene families of ginsenoside biosynthesis pathway and catalase gene(PgCAT)were evaluated by qRT-PCR,moreover,the relevance between gene expression and ginsenoside accumulation was also analyzed.The results indicated that 8 genes of PgHMGR2,PgFPS,PgSSl,PgSE1,PgDDS,PgPPDFS,PgPPTS,PgGT may be related to ginsenoside accumulation under chilling,especially PgDDS locates at the branching point for ginsenosides and sterols,provides tetracyclic skeleton for Dammarane-type ginsenosides,and the expression of PgDDS was related to ginsenoside accumulation under continuous and intermittent chilling.Thus we speculated that PgDDS was the key gene influencing ginsenoside accumulation under chilling treatments,and its transcriptional expression coordinated with other genes might be the reason for the accumulation of ginsenoside induced by chilling treatments in ginseng cells.The transcriptional expression of PgCAT indicated that chilling induced the oxidative stress,and the oxidative stress caused by continuous chilling is much stronger than intermittent chilling.Moreover,the SRAP molecular marker was adopted to screen differentially expressed genes under chilling treatments,and we got a partial gene named as PgF8-]that contains 299 bp nucleotides,which was closely related to chilling.The homology comparison of Blast showed that PgF8-1 is a new unreported gene in ginseng,and the mechanism of PgF8-1 under chilling treatments needed further research. |
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