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.

Ruihua Ren,Zhenwen Zhang,Sha Xie,Xiaofeng Yue,Junnan Li,Shuihuan Guo

doi:10.3389/fpls.2020.00321

Ruihua Ren, Zhenwen Zhang + Show 4 more

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https://doi.org/10.3389/fpls.2020.00321

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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.

Highlights

Plants fix inorganic C to produce carbohydrates via photosynthesis, which occurs in the mesophyll cells of mature leaves (Williams et al, 2000)
Seven members of the SWEET family that were highly expressed in grape berries (Chong et al, 2014) were investigated in this study (Supplementary Table 3), and the results showed that VvSWEET10 and VvSWEET15 were differentially expressed among the cultivars
VvSWEET15 and VvSS3 highly expressed in the grape berries when hexose began to accumulate

Summary

Introduction

Plants fix inorganic C to produce carbohydrates via photosynthesis, which occurs in the mesophyll cells of mature leaves (Williams et al, 2000). SS-SWEET Increases Hexose Content via long-distance phloem transportation (Ludewig and Flügge, 2013). This process is necessary to maintain plant and fruit growth. In terms of fruit-producing species, fruit is the major ‘sink’ in the reproductive growth stage, during which large amounts of photosynthates are stored in the vacuole as sucrose— such as that which occurs in tomato (Shammai et al, 2018) and apple (Zhen et al, 2018) fruit—or as hexoses (fructose and glucose), such as that which occurs in grape (Zhang et al, 2006) berries, affecting fruit quality (Kalt-Torres and Huber, 1987). Due to competition for sugar availability, sugar partitioning between vegetative growth and reproductive growth is vital with respect to increasing fruit yields and quality (Gifford et al, 1984)

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