Identification and characterization of flavonoid 3-O-glycosyltransferase gene CtUF3GT from safflower (Carthamus tinctorius L.) / 药学学报

UDP-glucose: flavonoid 3-O-glucosyltransferase (UF3GT) uses flavones, dihydroflavonol or anthocyanin as the acceptor and uridine 5′-diphosphate-sugar as the donor to catalyze the production of flavonoid 3-O-glycoside compounds. Based on sequence homology and transcriptome data, we screened and cloned a UF3GT gene named CtUF3GT (GenBank No. OM948976) from safflower. Biological information analysis demonstrate that CtUF3GT has highly conserved PSPG motif. The open reading frame of CtUF3GT is 1 446 bp, encoding 481 amino acids, with a presumed molecular weight of 52.36 kD and a theoretical isoelectric point of 5.33. Multiple sequence alignment indicate that CtUF3GT has a high homology with UF3GT from Asteraceae, and phylogenetic analysis showed that CtUF3GT clusters with functional identified UF3GTs from other species. The purified recombinant protein glucosylated kaempferol and quercetin to biosynthesis of kaempferol 3-O-glucoside and quercetin 3-O-glucoside, respectively. And CtUF3GT prefered to use kaempferol as substrate. qRT-PCR analysis showed that the UF3GT gene was most highly expressed in flowers, followed by leaves, with very low expression in bracts and stems, and no expression in roots. The expression of UF3GT gene showed a trend of increasing and then decreasing at different stages of flower development. The expression of CtUF3GT gene in safflower with different flower color was highly significant (P < 0.01) at S1, S2, S5, S6 and S7 stages of flower development, in which the expression of CtUF3GT in white safflower was 5.3 and 3.1 times higher than that in red safflower at S6 and S7 stages. This study lays the foundation for further exploring the role of CtUF3GT in the mechanism of safflower flavonoid secondary metabolite biosynthesis and accumulation.

Identification and functional characterization of 2,3-oxidosqualene cyclase genes family in Tripterygium wilfordii / 药学学报

italic>Tripterygium wilfordii Hook. f. is a valuable medicinal plant, with anti-tumor, anti-inflammatory, immunosuppressive and other pharmacological activities. Triterpenoids are one of the main active components that exert pharmacological effects. However, the content of triterpenoids dominated by triptolide is very low in Tripterygium wilfordii, and the analysis of the biosynthetic pathway of triterpenoids in Tripterygium wilfordii provides an effective new idea for obtaining these compounds. 2,3-Oxidosqualene cyclases (OSCs) are the key enzyme that catalyzes the formation of triterpene skeleton diversity. Based on the genome and transcriptome data of Tripterygium wilfordii, 16 OSC genes were identified and analyzed. Phylogenetic analysis showed that 16 TwOSC proteins could be mainly classified as four groups. They are β-amyrin synthase group, friedelin synthase group, multifunctional amyrin synthase and cycloartenol synthase group. TwOSC6 was successfully cloned. Functional characterization analysis revealed that TwOSC6 can catalyze the formation of α-amyrin and β-amyrin. This indicates that TwOSC6 is a multifunctional amyrin synthase. This provides new gene resources for the diversity of Tripterygium wilfordii triterpenoids, as well as new gene elements for biosynthesis triterpenoids.

Cloning and characterization of two rhamnose synthases from Sorbus aucuparia / 药学学报

Rhamnose synthase (RHM) is a key enzyme in the biosynthesis of uridine diphosphate rhamnose (UDP-Rha), reversibly converting uridine diphosphate-glucose (UDP-Glc) into UDP-Rha in the presence of NADH or NADPH. In this research, yeast extract (YE) was used to stimulate Sorbus aucuparia suspension cells. Based on a previous study of the transcriptome database of S. aucuparia suspension cells, two RHMs were cloned from S. aucuparia and named SaRHM1 (GenBank No.: MK213340) and SaRHM2 (GenBank No.: MK213341). The SaRHM1 gene contained a 2 007 bp open reading frame (ORF) encoding a polypeptide of 668 amino acids with a molecular weight of 75.25 kD, and a theoretical isoelectric point (pI) of 7.24. The SaRHM2 gene contained a 2 040 bp ORF encoding a polypeptide of 679 amino acids with a molecular weight of 76.26 kD and pI of 6.41. Bioinformatic analysis indicated that SaRHM1 and SaRHM2 contained two special sequences of GxxGxxG/A and YxxxK. Multiple sequence alignments and phylogenetic trees show that SaRHM1 and SaRHM2 have high sequence similarity with other plant species of RHMs. The results of enzyme activity assays in vitro revealed that both recombinant SaRHM1 and SaRHM2 are able to convert UDP-Glc into UDP-Rha. SaRHMs displayed maximum activity at 40 ℃ and a pH of 8 and 9, respectively. The Km values of SaRHM1 and SaRHM2 for UDP-Glc were 212.4 ± 56.70 and 361.0 ± 63.74 μmol·L-1, respectively, with Vmax values of 235.5 ± 18.98 and 516.5 ± 22.30 nmol·min-1·μg-1, respectively. This study reports the cloning and sequencing of RHMs from S. aucuparia and verifies their function, which likely provide rhamnose donors for the subsequent biosynthesis of rhamnosides.

Cloning and characterization of UDP-L-rhamnose synthase 1/2 from Fallopia multiflora / 药学学报

UDP-rhamnose is a rhamnose donor in a reaction catalyzed by UDP-rhamnose synthase (RHM), and plays an important role in the biosynthesis of rhamnoside compounds. The current literature suggests that there are only a few genes can encode the corresponding enzymes to participate in UDP-rhamnose biosynthesis in plants. In this study, two RHM genes (FmRHM1 & 2) were first cloned by using the transcriptomic data of Fallopia multiflora (Thunb) Harald and the multidimensional analysis, including bioinformatics, functional identification in vitro and tissue-specific expression analysis. The results showed that the open reading frame (ORF) of FmRHM1 & 2 genes both were 2 013 bp, encode proteins consisting of 670 amino acids with a calculated molecular mass of 75.6 kDa, and the theoretical isoelectric points of 6.20 and 7.19, respectively. Bioinformatic analysis also indicated that FmRHM1 & 2 contained 2 special sequences of GxxGxxG/A and YxxxK. The phylogenetic analysis showed that the FmRHM gene has a high homology with RHM of other species. The results of enzyme activity in vitro revealed that both recombinant FmRHM1 and FmRHM2 have catalytic activities for converting UDP-glucose into UDP-rhamnose. Measurements of tissue-specific expressions showed that the expression levels of FmRHM1 and FmRHM2 were lower in roots. On the contrary, the 2 genes showed significantly high expression in the stems and leaves. In conclusion, we have cloned and characterized the RHM gene function for the first time in F. multiflora. Here we have provided the preliminary data suggesting the need for further research on UDP-rhamnose biosynthesis by microorganisms.