UDP-glycosyltransferases (UGT) catalyze the conjugation of a range of diverse small lipophilic compounds with sugars to produce glycosides, playing an important role in the detoxification of xenobiotics and in the regulation of endobiotics in insects. Recent progress in genome sequencing has enabled an assessment of the extent of the UGT multigene family in insects. Here we report over 310 putative UGT genes identified from genomic databases of eight different insect species together with a transcript database from the lepidopteran Helicoverpa armigera. Phylogenetic analysis of the insect UGTs showed Order-specific gene diversification and inter-species conservation of this multigene family. Only one family (UGT50) is found in all insect species surveyed (except the pea aphid) and may be homologous to mammalian UGT8. Three families (UGT31, UGT32, and UGT305) related to Lepidopteran UGTs are unique to baculoviruses. A lepidopteran sub-tree constructed with 40 H. armigera UGTs and 44 Bombyx mori UGTs revealed that lineage-specific expansions of some families in both species appear to be driven by diversification in the N-terminal substrate binding domain, increasing the range of compounds that could be detoxified or regulated by glycosylation. By comparison of the deduced protein sequences, several important domains were predicted, including the N-terminal signal peptide, UGT signature motif, and C-terminal transmembrane domain. Furthermore, several conserved residues putatively involved in sugar donor binding and catalytic mechanism were also identified by comparison with human UGTs. Many UGTs were expressed in fat body, midgut, and Malpighian tubules, consistent with functions in detoxification, and some were expressed in antennae, suggesting a role in pheromone deactivation. Transcript variants derived from alternative splicing, exon skipping, or intron retention produced additional UGT diversity. These findings from this comparative study of two lepidopteran UGTs as well as other insects reveal a diversity comparable to this gene family in vertebrates, plants and fungi and show the magnitude of the task ahead, to determine biochemical function and physiological relevance of each UGT enzyme.

Capsaicin β-glucoside was isolated from the feces of Helicoverpa armigera, H. assulta and H. zea that fed on capsaicin-supplemented artificial diet. The chemical structure was identified by NMR spectroscopic analysis as well as by enzymatic hydrolysis. The excretion rates of the glucoside were different among the three species; those in the two generalists, H. armigera and H. zea, were higher than in a specialist, H. assulta. UDP-glycosyltransferases (UGT) enzyme activities measured from the whole larval homogenate of the three species with capsaicin and UDP-glucose as substrates were also higher in the two generalists. Compared among five different larval tissues (labial glands, testes from male larvae, midgut, the Malpighian tubules, and fatbody) from the three species, the formation of the capsaicin glucoside by one or more UGT is high in the fat body of all the three species as expected, as well as in H. assulta Malpighian tubules. Optimization of the enzyme assay method is also described in detail. Although the lower excretion rate of the unaltered capsaicin in H. assulta indicates higher metabolic capacity toward capsaicin than in the other two generalists, the glucosylation per se seems to be insufficient to explain the decrease of capsaicin in the specialist, suggesting H. assulta might have another important mechanism to deal with capsaicin more specifically.

Background : Glycosylation of natural compounds results in great diversity of secondary metabolites. Glycosylation steps are implicated not only in plants growth and development but also in plant defense responses to various environmental stresses. This process is mediated by members of a multigene superfamily glycosyltransferase (GT), which catalyze the transfer of single or multiple activated sugars to a wide range of substrates, thus influences their chemical property and bioactivity. Although its activity has been recognized for a long time and genes coding UGTs in several higher plants have been identified, specific function of GTs in detail still remains elusive. Methods and Results : Spatial and temporal expression patterns of a ginseng UDP-dependent glycosyltransferase, was analyzed by qRT-PCR. It was expressed highly in rhizome, upper root and youngest leaf compared that of other organs. Spacial expression was observed by GUS histochemical assay after generating promoter::GUS fusion. Noticeably, it expressed axillary branch as well as other organs tested by qRT-PCR. Overexpression of PgUGT in Arabidopsis resulted in fused organ in axillary branch. Stress responsiveness against various abiotic stresses and subcellular localization in Arabidopsis are also addressed. Conclusion : PgUGT phylogenetically closed to PgUGT71A27 involved in ginsenoside compound K (C-K) production. Considering that the C-K is not reported in raw ginseng material, further characterization of this gene may shed light on the biological function of C-K in ginseng growth and development. Organ fusion phenotype could be caused by defective growth of cells in boundary region, commonly regulated by phytohormones such as auxins or brassinosteroids, which in needs to be analyzed further.

Background : Platycodon grandiflorum is a perennial plant and a member of Camanulaceae family. Since ancient times, they have been using P. grandiflorum as an important medicinal plant in Korea. Platycodin D is the most abundant saponin derived from P. grandiflorum and pharmacologically active component. UDP-glycosyltransferases (UGTs) are important enzymes in the saponin biosynthesis. UGT is a glycosyltransferase and act on the final step of the secondary metabolite biosynthesis. Methods and Results : We tried to identify UGT genes related to saponin biosynthesis of P. grandiflorum through RNA-seq analysis. The sequencing was performed using Illumina Hi-Seq platform after cDNA library preparation. The produced reads were assembled using CLC Genomics Workbench software (CLC Bio, Inc.). We obtained 122,663 contigs and found 137 putative UGT genes. Familes of UGT71, UGT73, and UGT74 were selected as putative saponin biosynthesis related gene families using phylogenetic relationship analysis. qPCR condition about UGT73 is preheating 94℃ 180 sec, denaturation 94℃ 60 sec, annealing 53℃ 60 sec, extension 72℃ 90 sec, final extension 72℃ 600 sec, 45 cycles repeated. Conclusion : The results in this study could help to find the UGTs related to saponin biosynthesis pathway of P. grandiflorum.

Secondary plant metabolites undergo several modification reactions, including glycosylation and physiological functions. Glycosylation, which is mediated by UDP-glycosyltransferase (UGT), plays a role in the storage of secondary metabolites and in defending plants against stress. In this study, a UDP-glucosyltransferase cDNA was isolated from Brassica rapa hereinafter referred to as BrUGT. It has a full-length cDNA of 1,236 bp that contains a single open reading frame of 834 bp which encodes a polypeptide of 277 amino acid residues with a calculated mass of 31.19 kDa. BLASTX analysis hits a catalytic domain of glycos_transf_1 super family (c112012) that belongs to the glycosyltransferases group 1 with tetratricopeptide (TPR) regions. UGT gene expression analysis showed high mRNA transcripts in pistil, followed by petal, seed and calyx of flower in Brassica rapa. Furthermore, we constructed a recombinant pFLCIII vector carrying the BrUGT gene under the control of ubiquitin promoter and NOS terminator and transformed into rice using Agrobacterium tumefaciens. The UGT overexpressing rice lines were then characterized at the physiological and molecular levels. To further understand the biological function of BrUGT, transcriptional profiling of the gene in transgenic rice lines under cold, salt, PEG, H2O2, ABA and drought stress condition is underway.