Glutathione status correlates with different degrees of desiccation tolerance in three lichens

Glutathione-related mechanisms of coping with desiccation were studied in three lichens (Pseudevernia furfuracea, Peltigera polydactyla and Lobaria pulmonaria) with different degrees of tolerance. Reduced (GSH) and oxidised glutathione (GSSG), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH) were measured during short- and long-term desiccation, and subsequent rehydration. Glutathione was analysed by HPLC, and enzymes by spectrophotometry. Lichens were desiccated over silica gel, and rehydrated either in liquid water or water vapour. - Desiccation caused oxidation of almost all of the GSH. After short-term desiccation, rehydration caused rapid reduction of GSSG in all three species. Following long-term desiccation, P furfuracea (the most desiccation-tolerant lichen studied) rapidly increased GSH when rehydrated in liquid water or water vapour. However, in P polydactyla, neither method of rehydration re-established the initial GSH pool. After long-term desiccation, L. pulmonaria regenerated initial concentrations of GSH only when rehydrated in liquid water. Reduction of GSSG was correlated with re-establishment of the predesiccation activity of G6PDH, a key enzyme of the oxidative pentose shunt. This enzyme probably provides NADPH during the first stages of rehydration, when photosynthesis is not yet possible.