RESUMO
Enzyme promiscuity, a common property of many uridine diphosphate sugar-dependent glycosyltransferases (UGTs) that convert small molecules, significantly hinders the identification of natural substrates and therefore the characterization of the physiological role of enzymes. In this paper we present a simple but effective strategy to identify endogenous substrates of plant UGTs using LC-MS-guided targeted glycoside analysis of transgenic plants. We successfully identified natural substrates of two promiscuous Nicotiana benthamiana UGTs (NbUGT73A24 and NbUGT73A25), orthologues of pathogen-induced tobacco UGT (TOGT) from Nicotiana tabacum, which is involved in the hypersensitive reaction. While in N. tabacum, TOGT glucosylated scopoletin after treatment with salicylate, fungal elicitors and the tobacco mosaic virus, NbUGT73A24 and NbUGT73A25 produced glucosides of phytoalexin N-feruloyl tyramine, which may strengthen cell walls to prevent the intrusion of pathogens, and flavonols after agroinfiltration of the corresponding genes in N. benthamiana. Enzymatic glucosylation of fractions of a physiological aglycone library confirmed the biological substrates of UGTs. In addition, overexpression of both genes in N. benthamiana produced clear lesions on the leaves and led to a significantly reduced content of pathogen-induced plant metabolites such as phenylalanine and tryptophan. Our results revealed some additional biological functions of TOGT enzymes and indicated a multifunctional role of UGTs in plant resistance.
Assuntos
Ácidos Cumáricos/metabolismo , Glucose/metabolismo , Glicosiltransferases/genética , Nicotiana/genética , Doenças das Plantas/genética , Proteínas de Plantas/genética , Sesquiterpenos/metabolismo , Tiramina/análogos & derivados , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica de Plantas , Glicosídeos/metabolismo , Glicosilação , Glicosiltransferases/metabolismo , Doenças das Plantas/virologia , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/virologia , Proteínas de Plantas/metabolismo , Especificidade por Substrato , Nicotiana/metabolismo , Nicotiana/virologia , Vírus do Mosaico do Tabaco/fisiologia , Tiramina/metabolismo , FitoalexinasRESUMO
The transcriptional response of macrophages and dendritic cells to stimulation of pattern recognition receptors can be unexpectedly distinct. In this issue of Science Signaling, Watanabe et al. demonstrate that IL-2 is differentially induced by the closely related C-type lectin receptors Dectin-2 and Mincle and reveal early signaling through the adaptor protein FcRγ as a critical mechanism.