Hydrogen Gas Enhanced Seed Germination by Increasing Trehalose Biosynthesis in Cucumber

Hydrogen gas (H 2 ) and trehalose (Tre) are involved in various biological processes in plants. In the study, the roles of H 2 and Tre and their interaction during seed germination in cucumber ( Cucumis sativus L . ) were investigated. Our results showed that the effects of Tre on seed germination were dose-dependent, with a maximal biological response at 0.8% (w/v). The positive roles of hydrogen rich water (HRW, a H 2 donor) were blocked by a specific Tre inhibitor trehazolin (Thz), suggesting that Tre might be responsible for H 2 -induced seed germination. HRW and Tre increased the endogenous Tre level and the activity of trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). Simultaneously, the expression level of Tre metabolism-related genes was up-regulated by HRW and Tre. Additionally, the content of Tre, water soluble carbohydrate, glucose (Glu) and sucrose was increased by HRW and Tre. Meanwhile, the activity of starch-related enzymes including α-amylase (AMY), β-amylase (BMY) and total amylase enzyme was increased by HRW and Tre. Further, HRW and Tre significantly up-regulated the expression level of starch-related genes including AMY and BMY , which were inhibited by Thz, indicating that Tre might play a crucial role in H 2 -induced seed germination. Altogether, this study suggested that H 2 might induce seed germination by increasing Tre biosynthesis in cucumber.