De novo assembly and analysis of Polygonatum cyrtonema Hua and identification of genes involved in polysaccharide and saponin biosynthesis

Abstract

Background The investigation of molecular mechanisms involved in polysaccharides and saponin metabolism is critical for genetic engineering of Polygonatum cyrtonema Hua to raise major active ingredient content. Up to now, the transcript sequences are available for different tissues of P. cyrtonema, a wide range scanning about temporal transcript at different ages’ rhizomes was still absent in P. cyrtonema. Results Transcriptome sequencing for rhizomes at different ages was performed. Sixty-two thousand six hundred thirty-five unigenes were generated by assembling transcripts from all samples. A total of 89 unigenes encoding key enzymes involved in polysaccharide biosynthesis and 56 unigenes encoding key enzymes involved in saponin biosynthesis. The content of total polysaccharide and total saponin was positively correlated with the expression patterns of mannose-6-phosphate isomerase (MPI), GDP-L-fucose synthase (TSTA3), UDP-apiose/xylose synthase (AXS), UDP-glucose 6-dehydrogenase (UGDH), Hydroxymethylglutaryl CoA synthase (HMGS), Mevalonate kinase (MVK), 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase (ispF), (E)-4-hydroxy-3-methylbut-2-enyl-diphosphate synthase (ispG), 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (ispH), Farnesyl diphosphate synthase (FPPS). Finally, a number of key genes were selected and quantitative real-time PCR were performed to validate the transcriptome analysis results. Conclusions These results create the link between polysaccharides and saponin biosynthesis and gene expression, provide insight for underlying key active substances, and reveal novel candidate genes including TFs that are worth further exploration for their functions and values.

Identification of key gene networks controlling polysaccharide accumulation in different tissues of Polygonatum cyrtonema Hua by integrating metabolic phenotypes and gene expression profiles

“…GALE (DN159955_c0_g2 and DN11833_c0_g1) (Figure 9). Correlations between polysaccharide content and the expression of MPI, GMPP, GMDS, and GALE genes were observed by other reports in P. cyrtonema Hua (Wang et al, 2019;Li et al, 2022). Therefore, these results suggested that sucrose might be transported by SWEET (DN32250_c0_g1) to rhizomes, and then decomposed by INV to promote polysaccharide biosynthesis.…”

“…For instance, Wang et al found that polysaccharide content was low in the leaf (1.62%) (Wang et al, 2019). Most of the studies on polysaccharide accumulation were performed by examining the gene expression involved in the proposed pathway from sucrose to polysaccharide (Wang et al, 2019;Li et al, 2022). Furthermore, sucrose is the main form that is transported from source leaves to different sinks via SWEETs, SUTs, and/or ERDs transporters (Julius et al, 2017).…”

“…For example, Wang et al (2019) speculated the multiple genes encoding important enzymes, such as UDP glycosyltransferases (UGTs), and the transcription factors through comprehensive analyses of the transcriptome in leaf, root, and rhizome tissues. Besides, a positively correlated link between polysaccharide accumulation and the MPI , TSTA3 , AXS , and UGDH transcript levels was also suggested via the transcriptome sequencing for rhizomes at different ages ( Li et al, 2022 ).…”

“…Recently, some molecular studies on the genes related to polysaccharide biosynthesis of P. cyrtonema Hua have been published ( Wang et al, 2019 ; Li et al, 2022 ). For example, Wang et al (2019) speculated the multiple genes encoding important enzymes, such as UDP glycosyltransferases (UGTs), and the transcription factors through comprehensive analyses of the transcriptome in leaf, root, and rhizome tissues.…”

“…Besides, this transporter-regulated sucrose accumulation played a specific role in plant abiotic stress tolerance and adaptation ( Chandran, 2015 ; Eggert et al, 2016 ). Interestingly, in the rhizome of P. cyrtonema Hua, sucrose might act as a precursor for polysaccharide biosynthesis ( Wang et al, 2019 ; Li et al, 2022 ). However, whether or not, or how polysaccharide accumulation in rhizomes is modulated by sucrose synthesis and transported in leaf and/or stem remains unknown in P. cyrtonema Hua.…”