Fiche publication
Date publication
juillet 2021
Journal
The Plant cell
Auteurs
Membres identifiés du Cancéropôle Est :
Pr GAQUEREL Emmanuel
Tous les auteurs :
Heiling S, Llorca LC, Li J, Gase K, Schmidt A, Schäfer M, Schneider B, Halitschke R, Gaquerel E, Baldwin IT
Lien Pubmed
Résumé
The native diploid tobacco Nicotiana attenuata produces abundant, potent anti-herbivore defense metabolites known as 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) whose glycosylation and malonylation biosynthetic steps are regulated by jasmonate signaling. To characterize the biosynthetic pathway of HGL-DTGs, we conducted a genome-wide analysis of uridine diphosphate glycosyltransferases (UGTs) and identified 107 family-1 UGT members. The transcript levels of three UGTs were highly correlated with the transcript levels two key HGL-DTG biosynthetic genes: geranylgeranyl diphosphate synthase (NaGGPPS) and geranyllinalool synthase (NaGLS). NaGLS's role in HGL-DTG biosynthesis was confirmed by virus-induced gene silencing. Silencing the Uridine diphosphate (UDP)-rhamnosyltransferase gene UGT91T1 demonstrated its role in the rhamnosylation of HGL-DTGs. In vitro enzyme assays revealed that UGT74P3 and UGT74P4 use UDP-glucose for the glucosylation of 17-hydroxygeranyllinalool (17-HGL) to lyciumoside I. Plants with stable silencing of UGT74P3 and UGT74P5 were severely developmentally deformed, pointing to a phytotoxic effect of the aglycone. The application of synthetic 17-HGL and silencing of the UGTs in HGL-DTG-free plants confirmed this phytotoxic effect. Feeding assays with tobacco hornworm (Manduca sexta) larvae revealed the defensive functions of the glucosylation and rhamnosylation steps in HGL-DTG biosynthesis. Glucosylation of 17-HGL is therefore a critical step that contributes to the resulting metabolites' defensive function and solves the autotoxicity problem of this potent chemical defense.
Mots clés
Acyclic Monoterpenes, chemistry, Animals, Biosynthetic Pathways, Diterpenes, metabolism, Gene Silencing, Glycosides, metabolism, Glycosylation, Glycosyltransferases, metabolism, Herbivory, Larva, physiology, Manduca, physiology, Metabolomics, Necrosis, Plant Leaves, metabolism, Plants, Genetically Modified, Recombinant Proteins, metabolism, Nicotiana, metabolism
Référence
Plant Cell. 2021 07 2;33(5):1748-1770
