| Panax notoginseng is a medicinal plant with a long history and has a wide range of medicinal value.The secondary metabolite,Panax notoginseng saponins(PNS)is the main active component of Panax notoginseng,which has the functions of promoting blood circulation and removing blood stasis,clearing collaterals and activating arteries,inhibiting platelet aggregation and increasing blood flow to heart and brain.Squalene synthase gene is a key enzyme in the synthesis pathway of PNS.It can catalyze the synthesis of squalene from farnesic pyrophosphoric acid,and squalene is an essential substrate for the synthesis of PNS.In this study,we first identified nine PnSQS genes,and analyzed all SQS genes in detail by using bioinformatics methods such as gene structure,conserved motif,protein physicochemical properties and protein structure,then,the expression of PnSQSs in different tissues and under the hormone induction treatment of ABA,MeJA and SA were analyzed,and PnSQS5/-7/-8 genes were selected according to the experimental results.Then PnSQS5/-7/-8 were cloned from sanqi,and subcellular localization analysis and protein expression purification experiment were performed.The main results of this study are as follows:1.Except for PnSQS8,the other genes may be parallel homologous genes obtained by gene replication.During evolution,the PnSQS 5 and PnSQS 8 showed intron deletion and similar or same conserved motifs were found among genes with high sequence similarity.2.The secondary structure of PnSQS protein was dominated by α-helix,followed by irregular curling,the third was extended chain and the least was β-angle,the results of tertiary structure prediction showed that the tertiary structure model of PnSQS gene protein may tend to be true protein structure.3.Tissue expression pattern and hormone induction analysis showed that PnSQS5/-7/-8 were highly expressed in leaves and after treatment with ABA,MeJA and SA,they were expressed significantly increased.4.Subcellular localization showed that PnSQS5/-7/-8 was located in the cell membrane and nucleus.5.PnSQS5/-7/-8 protein was obtained by polyacrylamide gel electrophoresis analysis and purification. |
