The SlDOG1 Affect Biosynthesis of Steroidal Glycoalkaloids by Regulating GAME Expression in Tomato

Abstract

Steroidal alkaloids (SAs) and steroidal glycoalkaloids (SGAs) are common constituents of plant species belonging to the Solanaceae family. However, the molecular mechanism regulating the formation of SAs and SGAs remains unknown. Here, genome-wide association mapping was used to elucidate SA and SGA regulation in tomatoes: a SlGAME5-like glycosyltransferase (Solyc10g085240) and the transcription factor SlDOG1 (Solyc10g085210) were significantly associated with steroidal alkaloid composition. In this study, it was found that rSlGAME5-like can catalyze a variety of substrates for glycosidation and can catalyze SA and flavonol pathways to form O-glucoside and O-galactoside in vitro. The overexpression of SlGAME5-like promoted α-tomatine, hydroxytomatine, and flavonol glycoside accumulation in tomatoes. Furthermore, assessments of natural variation combined with functional analyses identified SlDOG1 as a major determinant of tomato SGA content, which also promoted SA and SGA accumulation via the regulation of GAME gene expression. This study provides new insights into the regulatory mechanisms underlying SGA production in tomatoes.

A metabolome and transcriptome survey to tap the dynamics of fruit prolonged shelf-life and improved quality within Greek tomato germplasm

“…According to previous studies, the gene performs the conversion of α-tomatine to hydroxytomatine and has been highly conserved through domestication to ensure a less bitter and harmless tomato fruit ( Cárdenas et al., 2016 ). Interestingly, another TF of the bZIP family, the DELAY OF GERMINATION 1 ( DOG1 ) that has been recently identified as a principal regulator of the pathway targeting GAME s transcription ( Zhao et al., 2023 ), was also enhanced in LSL, suggesting that the pathway is activated.…”

“…The majority of these metabolic routes have been well-characterized in tomato fruit, with a plethora of transgenic lines enriched in these compounds ( Verhoeyen et al., 2002 ; Bulley et al., 2012 ; Koukounaras et al., 2022 ). At the same time, tomato fruit contains high amounts of steroidal alkaloids and glycoalkaloids, such as α-tomatine, that are toxic for humans, thus considered as antinutritional factors ( Zhao et al., 2023 ). A wide group of genes related to glycoalkaloid metabolism ( GAME ) has been previously demonstrated to participate in glycoalkaloid synthesis, whereas through the process of ripening and a series of hydroxylation and glycosylation reactions, these genes convert tomatine to the non-toxic and non-bitter esculeoside A ( Cárdenas et al., 2016 ) that also possess some health benefits ( Nohara et al., 2010 ).…”