Coexpression of Sucrose Synthase and the SWEET Transporter, Which Are Associated With Sugar Hydrolysis and Transport, Respectively, Increases the Hexose Content in Vitis vinifera L. Grape Berries

Abstract

The sugar content of grape berries is affected by many factors. To explore the hexose content in different cultivars, the photosynthesis, vegetative, and reproductive biomass, as well as the enzyme activities and expression levels of genes related to sugar metabolism and sugar contents were measured. Samples were collected 70-110 days after anthesis (DAA), from Riesling (RI), Petit Manseng (PM), and Cabernet Sauvignon (CS) berries cultivated in the field. The results indicated that high expression levels of VvSWEET15 and VvSS3 and a high activity of sucrose synthase (SS) are associated with a higher hexose content in the berries of PM than in the berries of the other two cultivars. These genes promoted hexose accumulation in the berries by regulating sugar hydrolysis and transport. The results of this study indicate that active sugar hydrolysis and transport increase the hexose content of PM berries, which provides insights for grape berry quality improvement and breeding projects in wine production. Main Conclusion: The active VvSS3, sucrose synthase (SS), and VvSWEET15 increases the hexose content in Petit Manseng berries, which are associated with sugar hydrolysis and transport.

The Molecular Regulation of Carbon Sink Strength in Grapevine (Vitis vinifera L.)

“…Overexpression of VvSWEET10 in grapevine calli and tomatoes increased the glucose, fructose, and total sugar levels significantly ( Zhang et al, 2019 ). VvSWEET15 was highly expressed in three grape cultivars’ berries and obviously positively correlated with berry hexose content during ripening ( Ren et al, 2020 ). In summary, these findings demonstrated the role of VvSWEETs in sugar accumulation and biotic stress response.…”

“…Five SuSy genes (VvSS1-5) have been identified in the grape genome ( Zhu et al, 2017 ). VvSS3 was reported to co-express with VvSWEET15 to regulate sucrose hydrolysis and transport, leading to increase hexose accumulation in grapes ( Ren et al, 2020 ). Invertase hydrolyzes sucrose irreversibly into glucose and fructose and has a crucial function in establishing and maintaining sink metabolism, and hence considered to be a central molecular sink strength determinant ( Koch, 2004 ).…”

“…In grape, an increase in the expression and activity of CWINV was concomitant with a rise in apoplastic sugar concentration and osmotic pressure ( Zhang et al, 2006 ; Xie et al, 2009 ). While some studies reported invertase and hexose transporters are unnecessary for sugar differential accumulation among cultivars ( Ren et al, 2020 ), others found that it was mainly due to acid invertase activity ( Guan, 2011 ). However, no functional identification is focused on the member of VvSSs or invertase family in grape so far.…”

Data_Sheet_1.doc

“…Five SuSy genes (VvSS1-5) have been identified in the grape genome (Zhu et al, 2017). VvSS3 was reported to co-express with VvSWEET15 to regulate sucrose hydrolysis and transport, leading to increase hexose accumulation in grapes (Ren et al, 2020). Invertase hydrolyzes sucrose irreversibly into glucose and fructose and has a crucial function in establishing and maintaining sink metabolism, and hence considered to be a central molecular sink strength determinant (Koch, 2004).…”

“…(Zhang et al, 2006;Xie et al, 2009). While some studies reported invertase and hexose transporters are unnecessary for sugar differential accumulation among cultivars (Ren et al, 2020), others found that it was mainly due to acid invertase activity (Guan, 2011). However, no functional identification is focused on the member of VvSSs or invertase family in grape so far.…”