Protein Synthesis during Rehydration of Rapidly Dried Tortula ruralis: Evidence for Oxidation Injury

Rapidly dried Tortula ruralis, a drought-tolerant moss, is known to synthesize proteins on rehydration at a much lower rate than the slowly dried moss. The reasons for this low rate of protein synthesis are unclear. We have found that during rehydration of rapidly dried moss, there is a negative correlation between the rate of protein synthesis and the tissue levels of oxidized glutathione (GSSG) and lipid peroxidation. When rapidly dried moss, which is known to show extensive solute leakage, is rehydrated in the presence of 100 millimolar K⁺, 5 millimolar Mg²⁺, 1 millimolar ATP, and 1 millimolar GTP, either separately or together, there is no stimulation of protein synthesis. When it is hydrated in the presence of either 5 millimolar glucose-6-phosphate or 0.1 millimolar NADPH, protein synthesis is stimulated but the stimulation is transitory. A second addition of either of these two chemicals causes a second transient stimulation of protein synthesis. A transitory decrease in the rate of GSSG accumulation is observed during rehydration in the presence of glucose-6-phosphate or NADPH. Both glucose-6-phosphate and NADPH are known to reverse GSSG-induced inhibition of protein synthesis in rabbit reticulocyte lysate. Results of the present study suggest that the rate of protein synthesis during rehydration of rapidly dried moss is not limited by the availability of ions or energy sources. Since exogenously applied GSSG has been shown to inhibit in vivo and in vitro protein synthesis and since it is known to accumulate during rehydration of rapidly dried, but not slowly dried, moss, it is suggested that the low rate of protein synthesis during rehydration of the rapidly dried moss is, at least in part, due to endogenous GSSG.