Plant Secondary Product Glycosyltransferase Motif Research Articles

Genome-wide identification and characterization of UGT family in pigeonpea (Cajanus cajan) and expression analysis in abiotic stress

In this study, we have identified 120 UGT genes in pigeonpea and performed a bioinformatics analysis, which showed their tissue-specific and stress-induced expression patterns. Family 1 UDP-glycosyltransferases (UGTs; EC 2.4.1.x) are enzymes that glycosylate aglycones into glycoside-associated compounds. They play an important role in plant resistance to abiotic stresses by regulating the synthesis of plant hormones and secondary metabolites. However, in pigeonpea, the UGT family has not yet been reported. Here, 120 CcUGT genes were identified from the pigeonpea genome, which all contained the plant secondary product glycosyltransferase motif (PSPG). According to the phylogenetic relationship, 120 CcUGTs can be classified into 11 major groups. The CcUGTs are distributed on 10 chromosomes except chromosome 5. Homology modeling of CcUGT proteins and conserved motif search were used to predict the structure of 120 UGTs. Most protein structures can be predicted with high accuracy. After that, 11 representative CcUGT genes were selected for further analysis. We measured their specific expression in different tissues and the changes in transcription levels after stress. The results show that 11 genes are specific in different tissues and the expression of genes in leaves is higher than that of other tissues. In roots, CcUGT69 genes were highly expressed in salt and osmotic stresses, and CcUGT110 was up-regulated in low temperature injury. In leaves, most of the genes were up-regulated after stress treatment, and only CcUGT6, 37, 56 had little change in transcription levels. Overall, this study systematically analyses the UGT gene family in pigeonpea for the first time and provides some useful clues for further functional studies of UGT genes.

Genome-wide analysis of the family 1 glycosyltransferases in cotton.

Family 1 GT, designated as UGT, is the largest and most functionally important multigene family in the plant kingdom. In this study, we carried out a genome-wide identification, analysis, and comparison of 142, 146, and 196 putative UGTs from Gossypium raimondii, Gossypium arboreum, and Gossypium hirsutum, respectively. All members present the 44 amino-acid conserved consensus sequence termed the plant secondary product glycosyltransferase motif. According to the phylogenetic relationship among the cotton UGT proteins and those from other species, GrUGTs and GaUGTs could be classified into 16 major phylogenetic groups (A-P), whereas GhUGTs are classified into 15 major phylogenetic groups with a lack of group C. All cotton UGTs are dispersed throughout the chromosomes and are displayed in clusters with the same open reading frame orientation. The expansion of them appears to result from genome duplication and rearrangement. Two conserved introns, A and B, are detected in most of the intron-containing-UGTs in G. raimondii and G. arboreum, whereas only intron A is detected in the intron-containing-UGTs in G. hirsutum. Furthermore, expression patterns of the UGT genes in G. hirsutum wild type and its near isogenic fuzzless-lintless mutant at the stage of fiber initiation were analyzed using the RNA-seq data. Overall, this study not only deepens our understanding of the structure, phylogeny, evolution, and expression of cotton UGT genes, but also provides a solid foundation for further cloning and functional studies of the UGT family genes.

Udp-Glycosyltransferases of Plant Hormones

Summary UDP-glycosyltransferases (GTases, UGT) catalyze the transfer of the sugar moiety from the uridine-diphosphate-activated monosaccharide (e.g. uridine-diphosphate-5’-glucose, UDPG) molecule to the specific acceptor. Glycosides contain aglycons attached by a β-glycosidic bond to C1 of the saccharide moiety. Glycosylation is one of the mechanisms maintaining cellular homeostasis through the regulation of the level, biological activity, and subcellular distribution of the glycosylated compounds. The glycosides play various functions in plant cells, such as high-energy donors, or signalling molecules, and are involved in biosynthesis of cell walls. Plant cells exhibit structural and functional diversity of UGT proteins. The Arabidopsis thaliana genome contains more than 100 genes encoding GTases, which belong to 91 families, and are deposited in the CAZY (Carbohydrate Active enzyme) database (www. cazy.org/GlycosylTransferases.html). The largest UGT1 class is divided into 14 subfamilies (A-N), and includes proteins containing highly conserved 44-amino acid PSPG (Plant Secondary Product Glycosyltransferase) motif at the C-terminus. The PSPG motif is involved in the binding of UDP-sugar donors to the enzyme. UGT1’s catalyze the biosynthesis of both ester-type and ether-type conjugates of plant hormones (phytohormones). Conjugation of the phytohormones is an important mechanism that regulates the concentration of physiological active hormone levels during growth and development of plants. Glycoconjugation of phytohormones is widespread in the plant kingdom and all known phytohormones are able to form these conjugates. Most plant hormone conjugates do not indicate physiological activity, but rather are involved in transport, storage and degradation of the phytohormones. UDPG-dependent glycosyltransferases possess high substrate specificity, even within a given class of phytohormones. In many cases, the phenotype of plants is strongly affected by loss-of-function mutations in UGT genes. In this paper, advances in the isolation and characterization of glycosyltransferases of all plant hormones: auxin, brassinosteroids, cytokinin, gibberellin, abscisic acid, jasmonates, and salicylate is described

Characterization of three terpenoid glycosyltransferase genes in ‘Valencia’ sweet orange (Citrus sinensis L. Osbeck)

Three putative terpenoid UDP-glycosyltransferase (UGT) genes, designated CsUGT1, CsUGT2, and CsUGT3, were isolated and characterized in 'Valencia' sweet orange (Citrus sinensis L. Osbeck). CsUGT1 consisted of 1493 nucleotides with an open reading frame encoding 492 amino acids, CsUGT2 consisted of 1727 nucleotides encoding 504 amino acids, and CsUGT3 consisted of 1705 nucleotides encoding 468 amino acids. CsUGT3 had a 145 bp intron at 730-874, whereas CsUGT1 and CsUGT2 had none. The three deduced glycosyltransferase proteins had a highly conserved plant secondary product glycosyltransferase motif in the C terminus. Phylogenetic analysis showed that CsUGT1 and CsUGT3 were classified into group L of glycosyltransferase family 1, and CsUGT2 was classified into group D. Through Southern blotting analysis, CsUGT1 was found to have two copies in the sweet orange genome, whereas CsUGT2 and CsUGT3 had at least seven and nine copies, respectively. CsUGT1, CsUGT2, and CsUGT3 were constitutively expressed in leaf, flower, and fruit tissues. The results facilitate further investigation of the function of terpenoid glycosyltransferases in citrus and the biosynthesis of terpenoid glycosides in vitro.

Catalytic Key Amino Acids and UDP-Sugar Donor Specificity of a Plant Glucuronosyltransferase, UGT94B1: Molecular Modeling Substantiated by Site-Specific Mutagenesis and Biochemical Analyses

The plant UDP-dependent glucosyltransferase (UGT) BpUGT94B1 catalyzes the synthesis of a glucuronosylated cyanidin-derived flavonoid in red daisy (Bellis perennis). The functional properties of BpUGT94B1 were investigated using protein modeling, site-directed mutagenesis, and analysis of the substrate specificity of isolated wild-type and mutated forms of BpUGT94B1. A single unique arginine residue (R25) positioned outside the conserved plant secondary product glycosyltransferase region was identified as crucial for the activity with UDP-glucuronic acid. The mutants R25S, R25G, and R25K all exhibited only 0.5% to 2.5% of wild-type activity with UDP-glucuronic acid, but showed a 3-fold increase in activity with UDP-glucose. The model of BpUGT94B1 also enabled identification of key residues in the acceptor pocket. The mutations N123A and D152A decreased the activity with cyanidin 3-O-glucoside to less than 15% of wild type. The wild-type enzyme activity toward delphinidin-3-O-glucoside was only 5% to 10% of the activity with cyanidin 3-O-glucoside. Independent point mutations of three residues positioned near the acceptor B ring were introduced to increase the activity toward delphinidin-3-O-glucoside. In all three mutant enzymes, the enzymatic activity toward both acceptors was reduced to less than 15% of wild type. The model of BpUGT94B1 allowed for correct identification of catalytically important residues, within as well as outside the plant secondary product glycosyltransferase motif, determining sugar donor and acceptor specificity.