Differential proteomics of dehydration and rehydration in bryophytes: Evidence towards a common desiccation tolerance mechanism

All bryophytes evolved desiccation tolerance (DT) mechanisms during the invasion of terrestrial habitats by early land plants. Are these DT mechanisms still present in bryophytes that colonize aquatic habitats? The aquatic bryophyte Fontinalis antipyreticaHedw. was subjected to two drying regimes and alterations in protein profiles and sucrose accumulation during dehydration and rehydration were investigated. Results show that during fast dehydration, there is very little variation in protein profiles, and upon rehydration proteins are leaked. On the other hand, slow dehydration induces changes in both dehydration and rehydration protein profiles, being similar to the protein profiles displayed by the terrestrial bryophytes Physcomitrella patens (Hedw.) Bruch and Schimp. and, to what is comparable with Syntrichia ruralis (Hedw.) F. Weber and D. Mohr. During dehydration there was a reduction in proteins associated with photosynthesis and the cytoskeleton, and an associated accumulation of proteins involved in sugar metabolism and plant defence mechanisms. Upon rehydration, protein accumulation patterns return to control values for both photosynthesis and cytoskeleton whereas proteins associated with sugar metabolism and defence proteins remain high. The current results suggest that bryophytes from different ecological adaptations may share common DT mechanisms. Bryophytes developed desiccation tolerance (DT) mechanisms during early land invasion. Using a proteomic approach, we hypothesised that an aquatic and a terrestrial bryophyte would display similar responses at protein level during a desiccation event. Since currently there were developments of the proteomics and the genome of Physcomitrella patens, it is the moment to clarify the discussion about DT mechanisms with this information. A proteome of an aquatic bryophyte was performed and our results show that the protein variation patterns are similar to the terrestrial DT bryophytes Physcomitrella patens and also to Syntrichia ruralis. These results suggest that all bryophytes may possess common inducible DT mechanisms and the differences in morphology may determine the rate of dehydration and, thus, the capacity to withstand desiccation.