Genome-wide analysis of UDP-glycosyltransferase gene family and identification of members involved in flavonoid glucosylation in Chinese bayberry (Morella rubra)

Recent advancements in mogrosides: A review on biological activities, synthetic biology, and applications in the food industry

Mogrosides are low-calorie, biologically active sweeteners that face high production costs due to strict cultivation requirements and the low yield of monk fruit. The rapid advancement in synthetic biology holds the potential to overcome this challenge. This review presents mogrosides exhibiting antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and liver protective activities, with their efficacy in diabetes treatment surpassing that of Xiaoke pills (a Chinese diabetes medication). It also discusses the latest elucidated biosynthesis pathways of mogrosides, highlighting the challenges and research gaps in this field. The critical and most challenging step in this pathway is the transformation of mogrol into a variety of mogrosides by different UDP-glucosyltransferases (UGTs), primarily hindered by the poor substrate selectivity, product specificity, and low catalytic efficiency of current UGTs. Finally, the applications of mogrosides in the current food industry and the challenges they face are discussed.

The sugar donor specificity of plant family 1 glycosyltransferases

Plant family 1 glycosyltransferases (UGTs) represent a formidable tool to produce valuable natural and novel glycosides. Their regio- and stereo-specific one-step glycosylation mechanism along with their inherent wide acceptor scope are desirable traits in biotechnology. However, their donor scope and specificity are not well understood. Since different sugars have different properties in vivo and in vitro, the ability to easily glycodiversify target acceptors is desired, and this depends on our improved understanding of the donor binding site. In the aim to unlock the full potential of UGTs, studies have attempted to elucidate the structure-function relationship governing their donor specificity. These efforts have revealed a complex phenomenon, and general principles valid for multiple enzymes are elusive. Here, we review the studies of UGT donor specificity, and attempt to group the information into key concepts which can help shape future research. We zoom in on the family-defining PSPG motif, on two loop residues reported to interact with the C6 position of the sugar, and on the role of active site arginines in donor specificity. We continue to discuss attempts to alter and expand the donor specificity by enzyme engineering, and finally discuss future research directions.

Identification of Key Genes Associated with 1,2,6-Tri-O-galloyl-β-D-glucopyranose Accumulation in Camellia sinensis Based on Transcriptome Sequencing

Hydrolyzed tannin 1,2,6-tri-O-galloyl-β-D-glucopyranose (1,2,6-TGGP) possesses significant medicinal properties. However, little is known about its underlying molecular mechanisms. In this study, the levels of 1,2,6-TGGP in tea materials from different cultivars and leaf positions were compared. Additionally, one leaf and one bud sample from six tea cultivars with significant variations in 1,2,6-TGGP levels were analyzed using transcriptome high-throughput sequencing to identify the genes that are responsible for 1,2,6-TGGP accumulation. The sequencing results were mapped to the reference tea genome, revealing a total of 2735 differentially expressed genes (DEGs). This set included four UDP glycosyltransferase (UGTs) and six serine carboxypeptidases-like (SCPLs) genes. Among them, the upregulated SCPLs (CSS0032817) may directly participate in the acylation reaction of 1,2,6-TGGP. In addition, several classes of DEGs, including cytochrome P450, were significantly associated with the 1,2,6-TGGP content, which is potentially involved in their regulation. Overall, these results provide new insights into the molecular mechanism of 1,2,6-TGGP accumulation.

Glycosylation of Secondary Metabolites: A Multifunctional UDP-Glycosyltransferase, CsUGT74Y1, Promotes the Growth of Plants

Camellia sinensis contains numerous glycosylated secondary metabolites that provide various benefits to plants and humans. However, the genes that catalyze the glycosylation of multitype metabolites in tea plants remain unclear. Here, 180 uridine diphosphate-dependent glycosyltransferases that may be involved in the biosynthesis of glycosylated secondary metabolites were identified from the National Center for Biotechnology Information public databases. Subsequently, CsUGT74Y1 was screened through phylogenetic analysis and gene expression profiling. Compositional and induced expression analyses revealed that CsUGT74Y1 was highly expressed in tea tender shoots and was induced under biotic and abiotic stress conditions. In vitro enzymatic assays revealed that rCsUGT74Y1 encoded a multifunctional UGT that catalyzed the glycosylation of flavonoids, phenolic acids, lignins, and auxins. Furthermore, CsUGT74Y1-overexpressing Arabidopsis thaliana exhibited enhanced growth and accumulation of flavonol and auxin glucosides. Our findings provide insights into identifying specific UGTs and demonstrate that CsUGT74Y1 is a multifunctional UGT that promotes plant development.

Genome-Wide Analysis of Family-1 UDP-Glycosyltransferases in Potato (Solanum tuberosum L.): Identification, Phylogenetic Analysis and Determination of Response to Osmotic Stress

Family-1 UDP-glycosyltransferases (UGTs) are the most common and functional glycosyltransferases in the plant world. UGT is closely related to plant growth and the response to abiotic stress. However, despite systematic research, our understanding of potato UGT genes is still unclear. In this study, we identified 174 potato UGT proteins based on their conserved plant secondary product glycosyltransferase (PSPG) motifs. Phylogenetic analyses were used to compare these proteins with Arabidopsis UGTs and other plant UGTs, and it was found that they could be clustered into 18 distinct groups. Patterns of intron gain/loss and intron phases within potato UGTs revealed highly conserved intron insertion events. The promoter cis-elements of these 174 UGT genes were systematically investigated. The promoter regions of these UGT genes are known to contain various classes of cis-acting compounds. These include elements that are light-responsive, phytohormone-responsive, and stress-responsive. Transcriptome data analysis established that 25, 10, 6, and 4 of these 174 UGT genes were specifically expressed in leaves, roots, stolons, and young tubers, respectively. The mannitol-treated transcriptomic data showed thirty-eight UGT genes were significantly upregulated. The quantitative real-time PCR results showed that the four genes were all responsive to osmotic stress under a 10% PEG6000 treatment. The results of our study provide a basis for clarifying the molecular mechanism of potato osmotic stress resistance and better understanding its function in the future.

Genome-Wide Analysis of MYB Transcription Factors and Screening of MYBs Involved in the Red Color Formation in Rhododendron delavayi

Flower color is one of the crucial traits of ornamental plants. Rhododendron delavayi Franch. is a famous ornamental plant species distributed in the mountain areas of Southwest China. This plant has red inflorescence and young branchlets. However, the molecular basis of the color formation of R. delavayi is unclear. In this study, 184 MYB genes were identified based on the released genome of R. delavayi. These genes included 78 1R-MYB, 101 R2R3-MYB, 4 3R-MYB, and 1 4R-MYB. The MYBs were divided into 35 subgroups using phylogenetic analysis of the MYBs of Arabidopsis thaliana. The members of the same subgroup in R. delavayi had similar conserved domains and motifs, gene structures, and promoter cis-acting elements, which indicate their relatively conserved function. In addition, transcriptome based on unique molecular identifier strategy and color difference of the spotted petals, unspotted petals, spotted throat, unspotted throat, and branchlet cortex were detected. Results showed significant differences in the expression levels of R2R3-MYB genes. Weighted co-expression network analysis between transcriptome and chromatic aberration values of five types of red samples showed that the MYBs were the most important TFs involved in the color formation, of which seven were R2R3-MYB, and three were 1R-MYB. Two R2R3-MYB (DUH019226.1 and DUH019400.1) had the highest connectivity in the whole regulation network, and they were identified as hub genes for red color formation. These two MYB hub genes provide references for the study of transcriptional regulation of the red color formation of R. delavayi.