The effects of desiccation rate on enzyme and protein-synthesis dynamics in the desiccation-tolerant pteridophyte Selaginella lepidophylla

Abstract

The effects of desiccation rate on enzyme and protein-synthesis dynamics in the desiccation-tolerant pteridophyte Selaginella lepidophylla (Hook. & Grev.) Spring were examined in the laboratory. Detached, hydrated fronds were desiccated at four rates ranging from 5 to 150 h to frond curling at a water content of 0.35 g H₂O∙g dry weight⁻¹. Activities of 10 carbohydrate metabolism enzymes were determined following extraction from both desiccated and rehydrated fronds. Rehydration protein-synthesis rate was determined by the rate of [³⁵S]methionine incorporation and the protein-synthesis profile was examined with a dual-isotope, [³H]leucine and [¹⁴C]leucine incoporation and electrophoresis technique. Rate of desiccation significantly affected the conservation and (or) rehydration activity increases of four enzymes; intermediate desiccation rates generally maximized enzyme activity. Desiccation rate did not affect protein-synthesis rate late in rehydration but did appear to affect the nature of proteins synthesized relative to control patterns over a full 24-h recovery period. These results help explain why whole-plant photosynthetic recovery in S. lepidophylla is fastest after intermediate desiccation (ca. 50–100 h to frond curling), but they also indicate that the species is tolerant of a wide range of desiccation rates.