Glycoside-specific glycosyltransferases catalyze regio-selective sequential glucosylations for a sesame lignan, sesaminol triglucoside.
Plant J
; 101(5): 1221-1233, 2020 03.
Article
em En
| MEDLINE
| ID: mdl-31654577
ABSTRACT
Sesame (Sesamum indicum) seeds contain a large number of lignans, phenylpropanoid-related plant specialized metabolites. (+)-Sesamin and (+)-sesamolin are major hydrophobic lignans, whereas (+)-sesaminol primarily accumulates as a water-soluble sesaminol triglucoside (STG) with a sugar chain branched via ß1â2 and ß1â6-O-glucosidic linkages [i.e. (+)-sesaminol 2-O-ß-d-glucosyl-(1â2)-O-ß-d-glucoside-(1â6)-O-ß-d-glucoside]. We previously reported that the 2-O-glucosylation of (+)-sesaminol aglycon and ß1â6-O-glucosylation of (+)-sesaminol 2-O-ß-d-glucoside (SMG) are mediated by UDP-sugar-dependent glucosyltransferases (UGT), UGT71A9 and UGT94D1, respectively. Here we identified a distinct UGT, UGT94AG1, that specifically catalyzes the ß1â2-O-glucosylation of SMG and (+)-sesaminol 2-O-ß-d-glucosyl-(1â6)-O-ß-d-glucoside [termed SDG(ß1â6)]. UGT94AG1 was phylogenetically related to glycoside-specific glycosyltransferases (GGTs) and co-ordinately expressed with UGT71A9 and UGT94D1 in the seeds. The role of UGT94AG1 in STG biosynthesis was further confirmed by identification of a STG-deficient sesame mutant that predominantly accumulates SDG(ß1â6) due to a destructive insertion in the coding sequence of UGT94AG1. We also identified UGT94AA2 as an alternative UGT potentially involved in sugar-sugar ß1â6-O-glucosylation, in addition to UGT94D1, during STG biosynthesis. Yeast two-hybrid assays showed that UGT71A9, UGT94AG1, and UGT94AA2 were found to interact with a membrane-associated P450 enzyme, CYP81Q1 (piperitol/sesamin synthase), suggesting that these UGTs are components of a membrane-bound metabolon for STG biosynthesis. A comparison of kinetic parameters of these UGTs further suggested that the main ß-O-glucosylation sequence of STG biosynthesis is ß1â2-O-glucosylation of SMG by UGT94AG1 followed by UGT94AA2-mediated ß1â6-O-glucosylation. These findings together establish the complete biosynthetic pathway of STG and shed light on the evolvability of regio-selectivity of sequential glucosylations catalyzed by GGTs.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Glicosiltransferases
/
Lignanas
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Sesamum
/
Vias Biossintéticas
/
Glucosídeos
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Plant J
Assunto da revista:
BIOLOGIA MOLECULAR
/
BOTANICA
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Japão