Light-dependent (250 or 500 µmol/m²/s, red/far-red: 15/1; 250 µmol/m²/s and red/far-red: 10/1) adjustment of glutathione metabolism during cold acclimation (5°C, 7 d) was compared in four wheat genotypes (14-day-old) differing in freezing tolerance. Only the shoot fresh weight of the two tolerant genotypes increased during cold, regardless of light conditions. Their electrolyte leakage was decreased in high light intensity. Cold greatly increased both the amount of γ-glutamylcysteine (glutathione precursor) and cysteinylglycine (degradation product) in all genotypes grown in high intensity and far-red lights, and consequently, the ratio of their oxidised forms exhibited a great decrease. However, cold induced a fivefold increase in the amount of glutathione and hydroxymethylglutathione disulphides only in the two sensitive genotypes grown in far-red light. In general, the activities of the four enzymes of ascorbate–glutathione cycle were decreased by cold, except for the two tolerant genotypes cultivated in high light intensity. The gene expression studies did not reveal any transcriptional control of the changes observed at metabolite and activity levels. Our results show that both high intensity and far-red lights are involved in the control of the cold-induced changes in the amount/activity of the studied antioxidants, and some of these alterations have positive correlation with the level of freezing tolerance.

中文翻译：

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不同抗冻性小麦品种冷驯化过程中谷胱甘肽代谢光依赖变化的差异

光依赖性（250 或 500 µmol/m ² /s，红光/远红光：15/1；250 µmol/m ²/s 和红色/远红色：10/1) 比较冷适应（5°C，7 天）期间谷胱甘肽代谢的调整，比较了四种不同抗冻性的小麦基因型（14 天龄）。无论光照条件如何，只有两种耐受基因型的芽鲜重在寒冷期间增加。在高光强度下，它们的电解质泄漏减少。寒冷使在高强度和远红光下生长的所有基因型中γ-谷氨酰半胱氨酸（谷胱甘肽前体）和半胱氨酰甘氨酸（降解产物）的量都大大增加，因此它们的氧化形式的比例大大降低。然而，仅在远红光下生长的两种敏感基因型中，寒冷导致谷胱甘肽和羟甲基谷胱甘肽二硫化物的量增加了五倍。一般来说，除了在高光强度下培养的两种耐受基因型外，抗坏血酸-谷胱甘肽循环的四种酶的活性因寒冷而降低。基因表达研究没有揭示在代谢物和活性水平上观察到的变化的任何转录控制。我们的研究结果表明，高强度和远红光都参与了对寒冷引起的所研究抗氧化剂数量/活性变化的控制，其中一些变化与耐冻性水平呈正相关。