Potential application of the Oryza sativa monodehydroascorbate reductase gene (OsMDHAR) to improve the stress tolerance and fermentative capacity of Saccharomyces cerevisiae

Monodehydroascorbate reductase (MDHAR; EC 1.6.5.4) is an important enzyme for ascorbate recycling. To examine whether heterologous expression of MDHAR from Oryza sativa (OsMDHAR) can prevent the deleterious effects of unfavorable growth conditions, we constructed a transgenic yeast strain harboring a recombinant plasmid carrying OsMDHAR (p426GPD::OsMDHAR). OsMDHAR-expressing yeast cells displayed enhanced tolerance to hydrogen peroxide by maintaining redox homoeostasis, proteostasis, and the ascorbate (AsA)-like pool following the accumulation of antioxidant enzymes and molecules, metabolic enzymes, and molecular chaperones and their cofactors, compared to wild-type (WT) cells carrying vector alone. The addition of exogenous AsA or its analogue isoascorbic acid increased the viability of WT and ara2Δ cells under oxidative stress. Furthermore, the survival of OsMDHAR-expressing cells was greater than that of WT cells when cells at mid-log growth phase were exposed to high concentrations ...