The effects of pseudophosphorylation on Vitis riparia dehydrin structure and function

Plants undergo a wide range of deleterious effects as a result of exposure to abiotic stress, such as cold, salinity, and drought conditions. Some of these effects include protein denaturation and aggregation, membrane leakage and phase transitions, and DNA damage. One protective measure includes the expression of dehydrins, which are members of the group 2 LEA protein family. Several studies have shown that the S-segment, a serine-rich tract found in many dehydrins, can be phosphorylated in vivo. The main functional role of this phosphorylation appears to recruit the dehydrin to the nucleus, though this is not an absolute requirement. Here, we investigate whether pseudophosphorylation (i.e. the substitution of serine residues with glutamate) had any effect on the protection of proteins, membranes and DNA using VrDHN1 as a model YSK₂ dehydrin. The changes resulted in improved protection of lactate dehydrogenase from freeze-thaw damage and caused an increase in α-helicity after binding to SDS micelles. Pseudophosphorylation was found to reduce DNA binding but had no effect on the protection of DNA from ROS damage. In addition to a possible role in nuclear localization, phosphorylation may result in a tuning of dehydrin function toward improved protective ability.