Water deficit (WD) has adverse effects on plant growth, and acclimation requires responses allowing primary metabolism to continue. Resurrection plants can serve as model system to gain insight into metabolic regulation during WD. We herein report the response of a resurrection lycophyte, Selaginella bryopteris, to dehydration-rehydration cycle with emphasis on ammonium metabolism. Dehydration of S. bryopteris fronds resulted in decrease of total protein and increase of free ammonium levels and the effect was reversed on rehydration. The proline content increased twice after 24 h of dehydration, which again recovered to background levels comparable to that at full turgor state. The specific activity of glutamine synthetase (GS) didn’t change significantly till 6 h and then declined by 21% after 24 h of dehydration, whereas specific activities of glutamate synthase (GOGAT) and aminating glutamate dehydrogenase (GDH) were enhanced significantly during dehydration. The deaminating activity of GDH also increased during dehydration albeit at a slower rate. Immunoblot analysis indicated overexpression of GS and GDH polypeptides during dehydration and their levels declined on rehydration. The results suggested significant role of GDH along with GS/GOGAT in production of nitrogen-rich amino acids for desiccation tolerance. Unlike higher plants S. bryopteris expressed GS only in cytosol. The enzyme had pH and temperature optima of 5.5 and 60°C, respectively, and it retained 96% activity on preincubation at 60°C for 30 min indicating thermostability. Hence, like higher plants the cytosolic GS from S. bryopteris has a conserved role in stress tolerance.

水分亏缺 (WD) 对植物生长有不利影响，适应环境需要做出反应，使初级代谢得以继续。复活植物可以作为模型系统来深入了解 WD 期间的代谢调节。我们在此报告了复活石松植物 Selaginella bryopteris对脱水-补液循环的反应，重点是铵代谢。S. bryopteris的脱水叶子导致总蛋白减少和游离铵水平增加，并且对补液的影响逆转。脱水 24 小时后脯氨酸含量增加了两倍，再次恢复到与完全膨胀状态相当的背景水平。谷氨酰胺合成酶（GS）的比活性在脱水6 h前没有明显变化，然后在脱水24 h后下降21%，而谷氨酸合成酶（GOGAT）和氨基化谷氨酸脱氢酶（GDH）的比活性在脱水过程中显着增强. GDH 的脱氨活性也在脱水过程中增加，尽管速度较慢。免疫印迹分析表明，GS 和 GDH 多肽在脱水过程中过度表达，并且它们的水平在补液时下降。结果表明，GDH 和 GS/GOGAT 在生产耐干燥的富氮氨基酸中具有重要作用。不同于高等植物S. bryopteris仅在胞质溶胶中表达 GS。该酶的最适 pH 值和温度分别为 5.5 和 60°C，在 60°C 下预孵育 30 分钟时，它保留了 96% 的活性，表明其具有热稳定性。因此，与高等植物一样，来自S. bryopteris的细胞溶质 GS在胁迫耐受中具有保守的作用。