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 ...单脱氢抗坏血酸还原酶（Monodehydroascorbate reductase，MDHAR；EC 1.6.5.4）是参与抗坏血酸循环（ascorbate recycling）的重要酶类。为探究水稻（Oryza sativa）来源的单脱氢抗坏血酸还原酶（Oryza sativa Monodehydroascorbate reductase，OsMDHAR）的异源表达（heterologous expression）能否抵御不良生长条件带来的有害效应，本研究构建了携带重组质粒（recombinant plasmid）p426GPD::OsMDHAR的转基因酵母菌株（transgenic yeast strain）。与仅携带空载体的野生型（wild-type，WT）酵母细胞相比，表达OsMDHAR的酵母细胞通过维持氧化还原稳态（redox homoeostasis）、蛋白质稳态（proteostasis）以及抗坏血酸（ascorbate，AsA）样池，并通过积累抗氧化酶与抗氧化分子（antioxidant enzymes and molecules）、代谢酶（metabolic enzymes）、分子伴侣及其辅因子（molecular chaperones and their cofactors），显著提升了对过氧化氢（hydrogen peroxide）的耐受能力。外源添加AsA或其类似物异抗坏血酸（isoascorbic acid）可提高野生型与ara2Δ细胞在氧化胁迫（oxidative stress）下的存活率。进一步研究发现，当处于对数生长中期（mid-log growth phase）的细胞暴露于高浓度……时，表达OsMDHAR的细胞存活率显著高于野生型细胞。