Functional regulation of ginsenoside biosynthesis by RNA interferences of a UDP-glycosyltransferase gene in Panax ginseng and Panax quinquefolius

Abstract

Panax ginseng (Asian ginseng) and Panax quinquefolius (American ginseng) have been used as medicinal and functional herbal remedies worldwide. Different properties of P. ginseng and P. quinquefolius were confirmed not only in clinical findings, but also at cellular and molecular levels. The major pharmacological ingredients of P. ginseng and P. quinquefolius are the triterpene saponins known as ginsenosides. The P. ginseng roots contain a higher ratio of ginsenoside Rg1:Rb1 than that in P. quinquefolius. In ginseng plants, various ginsenosides are synthesized via three key reactions: cyclization, hydroxylation and glycosylation. To date, several genes including dammarenediol synthase (DS), protopanaxadiol synthase and protopanaxatriol synthase have been isolated in P. ginseng and P. quinquefolius. Although some glycosyltransferase genes have been isolated and identified association with ginsenoside synthesis in P. ginseng, little is known about the glycosylation mechanism in P. quinquefolius. In this paper, we cloned and identified a UDP-glycosyltransferase gene named Pq3-O-UGT2 from P. quinquefolius (GenBank accession No. KR106207). In vitro enzymatic activity experiments biochemically confirmed that Pq3-O-UGT2 catalyzed the glycosylation of Rh2 and F2 to produce Rg3 and Rd, and the chemical structure of the products were confirmed susing high performance liquid chromatography electrospray ionization mass spectrometry (HPLC/ESI-MS). High sequence similarity between Pq3-O-UGT2 and PgUGT94Q2 indicated a close evolutionary relationship between P. ginseng and P. quinquefolius. Moreover, we established both P. ginseng and P. quinquefolius RNAi transgenic roots lines. RNA interference of Pq3-O-UGT2 and PgUGT94Q2 led to reduce levels of ginsenoside Rd, protopanaxadiol-type and total ginsenosides. Expression of key genes including protopanaxadiol and protopanaxatriol synthases was up-regulated in RNAi lines, while expression of dammarenediol synthase gene was not obviously increased. These results revealed that P. quinquefolius was more sensitive to the RNAi of Pq3-O-UGT2 and PgUGT94Q2 when compared with P. ginseng.

Progress on the Studies of the Key Enzymes of Ginsenoside Biosynthesis

“…The identity of UGTPg45 and PgUGT74AE2 was 95.4%, while the identity of UGTPg29 and PgUGT94Q2 was 99.77%. Lu et al [ 47 ] cloned and identified a UGT gene named Pq3-O-UGT2 from P. quinquefolius . In vitro enzymatic assay confirmed that Pq3-O-UGT2 catalyzed the glycosylation of Rh2 and F2 to produce Rg3 and Rd.…”

Hybrid sequencing of the Gynostemma pentaphyllum transcriptome provides new insights into gypenoside biosynthesis

“…Five UGTs were identified from P. ginseng , including UGTPg1, UGTPg100, UGTPg101, PgUGT94Q2 and PgUGT74AE2. PgUGT74AE2 can catalyze the glycosylation of C3-OH of protopanaxadiol and compound K to form ginsenoside Rh2 and F2, respectively [24]; PgUGT94Q2 can catalyze Rh2 and F2 to form Rg3 and Rd., respectively, by forming a β-1,2-glycosidic linkage [24, 25]; UGTPg1 was characterized to glycosylate the C20-OH of PPD and PPT to produce compound K and ginsenoside F1, respectively [26]; UGTPg101 can catalyze the glycosylation of C20-OH of PPT and C6-OH of F1 to produce F1 and Rg1, respectively [27]; UGTPg100 can catalyze the glycosylation of C6-OH of PPT and F1 to form ginsenoside Rh1 and Rg1, respectively [27]. Transcription factors (TFs) play crucial roles in the regulation of secondary metabolite biosynthesis [28, 29].…”

Ascertaining the Paradigm of Secondary Metabolism Enhancement through Gene Level Modification in Therapeutic Plants

“…Deng et al 2017 [59] Panax quinquefolius Biosynthesis of protopanaxadiol-group ginsenosides UDP-glucosyltransferase gene RNA interference Lu et al 2017 [60] Panax quinquefolius Ginsenoside synthesis Down-regulation of UDP-Glycosyltransferase gene RNA interference Lu et al 2017 [61] Papaver somniferum Salutaridinol 7-O-acetyltransferase (SalAT)…”