Dehydrin-like proteins in desiccation tolerance in intertidal seaweeds

The intertidal red alga Porphyra occurs higher locally in New England than any other intertidal seaweed and is emerged twice a day which can last up to 8 hours per tide. It experiences a drastic change of water content during its emergence, which is very different from what happens in desiccation tolerant land plants. It is very likely that Porphyra may possess unique mechanisms in desiccation tolerance. Though the primary focus of past studies in desiccation tolerance in intertidal seaweeds has been the role of ROS metabolism, past investigations on two species of Porphyra have suggested that ROS metabolism is not involved. Dehydrin-like proteins are more likely to involved in the desiccation tolerance in P. umbilicalis and not in P. yezoensis. In this study, the presence and role of these dehydrin-like proteins were evaluated in P. umbilicalis and P. yezoensis. The results of this study indicate that a dehydrin-like protein was present in the desiccation tolerant P. umbilicalis but not in the desiccation sensitive P. yezoensis. These constitutively expressed dehydrin-like proteins were extremely hydrophilic under dehydrative conditions and thermally stable. During desiccation, P. umbilicalis fractions are able to suppress protein aggregation and inactivation of citrate synthase. Although these dehydrin-like proteins are present in P. umbilicalis , a survey of three other intertidal algae revealed that their occurrence may not be common in intertidal algae.