Open AccessOverexpression of Sr UGT 76G1 in Stevia alters major steviol glycosides composition towards improved quality
Author(s) -
Kim Mi Jung,
Zheng Junshi,
Liao Ming Hui,
Jang InCheol
Publication year - 2019
Publication title -
plant biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.525
H-Index - 115
eISSN - 1467-7652
pISSN - 1467-7644
DOI - 10.1111/pbi.13035
Subject(s) - stevioside , rebaudioside a , steviol , stevia , glycoside , glucosyltransferase , biology , food science , stevia rebaudiana , botany , biochemistry , chemistry , horticulture , enzyme , medicine , alternative medicine , pathology
Summary Steviol glycosides ( SG s) are extracted from Stevia leaves for use as a natural sweetener. Among SG s, stevioside is most abundant in leaf extracts followed by rebaudioside A (Reb A). However, Reb A is of particular interest because of its sweeter and more pleasant taste compared to stevioside. Therefore, the development of new Stevia varieties with a higher Reb A to stevioside ratio would be desirable for the production of higher quality natural sweeteners. Here, we generated transgenic Stevia plants overexpressing Stevia UDP ‐glycosyltransferase 76G1 ( Sr UGT 76G1 ) that is known to convert stevioside to Reb A through 1,3‐β‐ d ‐glucosylation in vitro . Interestingly, by overexpressing Sr UGT 76G1 , the Reb A to stevioside ratio was drastically increased from 0.30 in wild‐type ( WT ) plants up to 1.55 in transgenic lines without any significant changes in total SG s content. This was contributed by a concurrent increase in Reb A content and a decrease in stevioside content. Additionally, we were able to find an increase in the Reb C to dulcoside A ratio in transgenic lines. Using the glutathione S‐transferase‐tagged Sr UGT 76G1 recombinant protein for an in vitro glucosyltransferase assay, we further demonstrated that Reb C can be produced from the glucosylation of dulcoside A by Sr UGT 76G1. Transgenic Stevia plants having higher Reb A to stevioside ratio were visually indistinguishable from WT plants. Taken together, our results demonstrate that the overexpression of Sr UGT 76G1 in Stevia is an effective way to generate new Stevia varieties with higher proportion of the more preferred Reb A without compromising on plant development.