Induced sulfur metabolism by sulfur dioxide maintains postharvest quality of 'Thompson Seedless' grape through increasing sulfite content.

Background: The commercial preservation of table grapes largely depends on the application of sulfur dioxide (SO ₂ ). However, little is known about whether SO ₂ participates in sulfur metabolism to improve the postharvest quality of table grapes. In this study, the contents of sulfur-containing compounds, activities of enzymes, and expression of genes involved in sulfur metabolism in table grapes (Vitis vinifera cv. Thompson Seedless) were evaluated.
Results: The results indicated that SO ₂ treatment maintained the postharvest quality of table grapes. The sulfite content in rachises and berries, but not the sulfate content, increased in response to SO ₂ treatment. SO ₂ caused high activities of sulfite reductase, O-acetylserine (thiol)-lyase, and γ-glutamylcysteine synthetase, thereby increasing the contents of cysteine, hydrogen sulfide, and glutathione in the rachises and berries. The expression of VvSURTL, VvATPS1, VvATPS2, and VvAPR3 decreased in response to SO ₂ treatment; however, the transcript levels of VvSiR1 and VvOASTL exhibited the opposite tendency.
Conclusion: These findings indicated that the sulfite converted from SO ₂ participated in sulfur metabolism and maintained the postharvest quality of table grapes by modulating the contents of metabolites, activities of enzymes, and expression of genes related to sulfur metabolism. © 2021 Society of Chemical Industry.
(© 2021 Society of Chemical Industry.)