Monoterpenols serve various biological functions and accumulate in grape (Vitis vinifera), where a major fraction occurs as nonvolatile glycosides. We have screened the grape genome for sequences with similarity to terpene URIDINE DIPHOSPHATE GLYCOSYLTRANSFERASES (UGTs) from Arabidopsis (Arabidopsis thaliana). A ripening-related expression pattern was shown for three candidates by spatial and temporal expression analyses in five grape cultivars. Transcript accumulation correlated with the production of monoterpenyl b-D-glucosides in grape exocarp during ripening and was low in vegetative tissue. Targeted functional screening of the recombinant UGTs for their biological substrates was performed by activity-based metabolite profiling (ABMP) employing a physiologic library of aglycones built from glycosides isolated from grape. This approach led to the identification of two UDP-glucose:monoterpenol b-D-glucosyltransferases. Whereas VvGT14a glucosylated geraniol, R,S-citronellol, and nerol with similar efficiency, the three allelic forms VvGT15a, VvGT15b, and VvGT15c preferred geraniol over nerol. Kinetic resolution of R,S-citronellol and R,S-linalool was shown for VvGT15a and VvGT14a, respectively. ABMP revealed geraniol as the major biological substrate but also disclosed that these UGTs may add to the production of further glycoconjugates in planta. ABMP of aglycone libraries provides a versatile tool to uncover novel biologically relevant substrates of small-molecule glycosyltransferases that often show broad sugar acceptor promiscuity.Plant secondary metabolites are frequently decorated with Glc that is transferred from uridine diphosphoglucose by a so-called family 1 URIDINE DIPHOSPHATE GLUCOSYLTRANSFERASE (UGT; Caputi et al., 2012). Since the glucosylation process can be envisaged as a simple nucleophilic displacement reaction of Secondorder Nucleophilic Substitution type, the product is a b-glucoside. A remarkably large array of different small molecules is glucosylated in planta, including terpenoids, alkaloids, cyanohydrins, and glucosinolates, as well as flavonoids, isoflavonoids, anthocyanidins, and phenylpropanoids. In grape (Vitis vinifera) alone, more than 200 different glucosides have been identified, and there is special interest in those glucoconjugates, which can contribute to wine flavor after the hydrolytic release of volatiles during the biotechnological vinification sequence leading from grape to aged wine (Wirth et al., 2001). These flavorless glucoconjugates accumulate in grape berries during maturation and can be grouped according to their linked aglycones into monoterpenes, C13-norisoprenoids, aliphatic alcohols, and shikimatederived benzoids and phenylpropanoids (Sefton et al., 1996). It still remains an open question how this large number of structurally different flavor precursors is actually glucosylated in vivo, because the in vitro activities of single UGTs show large differences in the individual range of acceptors. Some UGTs are considered highly specific with respect to substrate ...

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The allochthonous calcarean sponge Paraleucilla magna has proliferated in the western Mediterranean during the last decade, where it currently shows a highly patchy distribution with dense populations in the neighboring of sea farms and slightly eutrophised marinas, and more sparse populations in well-preserved habitats. To gain knowledge about the species invasive capacity, we studied spatial genetic differentiation and structure, clonality, and temporal differentiation, in three close populations of P. magna at the NE of the Iberian Peninsula, in three successive years. The study hypothesis was that the species is able to proliferate under favorable conditions in newly colonized habitats but populations can easily disappear where perturbations occur with some frequency. Samples were genotyped for nine polymorphic microsatellites. Spatial genetic structure was found in the three populations of 2006. One population disappeared in 2007, and the other two remained slightly differentiated, while the three populations were in place again in 2008, and showed very low (but significant) F ST values, and non-significant D values. Low but statistically significant differentiation also occurred for the three populations between years. Results showed high-allele diversity, but heterozygote deficit and changes in allele frequencies in the populations over the 3 years, which are consistent with some genetic drift. The whole population descriptors pointed to the species as a good opportunistic colonizer as it has been hypothesized, but highly sensitive to stochastic events affecting recruitment. This suggests a high impact of the species in favorable habitats (sea culture and sheltered zones) and a low-medium influence in native communities.

Vinification of grapes (Vitis vinifera) exposed to forest fire smoke can yield unpalatable wine due to the presence of taint compounds from smoke and the release of smoke derived volatiles from their respective glycosides during the fermentation process or in-mouth during consumption. To identify glycosyltransferases (GTs) involved in the formation of glycosidically bound smoke-derived volatiles we performed gene expression analysis of candidate GTs in different grapevine tissues. Second, substrates derived from bushfire smoke or naturally occurring in grapes were screened with the candidate recombinant GTs. A resveratrol GT (UGT72B27) gene, highly expressed in grapevine leaves and berries was identified to be responsible for the production of the phenolic glucosides. UGT72B27 converted the stilbene trans-resveratrol mainly to the 3-Oglucoside. Kinetic analyses yielded specificity constants (k cat /K M ) of 114, 17, 9, 8, and 2 mM −1 s −1 for guaiacol, trans-resveratrol, syringol, methylsyringol, and methylguaiacol, respectively. This knowledge will help to design strategies for managing the risk of producing smoke-affected wines.

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