Water Stress-Responsive 23 kDa Polypeptide from Rice Seedlings is Boiling stable and is Related to the RAB16 Family of Proteins

Abstract

Summary The response of rapidly growing young seedlings of certain indica rice ( Oryza sativa L. Cvs) cultivars to polyethylene glycol (PEG)-mediated water stress and abscisic acid (ABA) treatment was investigated. Several water stress-responsive proteins were identified by SDS-PAGE and one such protein, namely the 23 kDa polypeptide, was purified. Using antibodies raised against it, we proved that this protein was also responsive to air drying (desiccation) of seedlings and ABA treatment but not to NaC1 and cold treatment. Further, Western analysis revealed that the 23 kDa protein is immunologically related to the RAB16 family of proteins. Finally, we demonstrated that the 23 kDa polypeptide is boiling stable. In view of its appearance in response to a variety of water stress conditions in both sensitive and tolerant cultivars, its immunological identity with the RAB16 protein and its novel feature of boiling stability, it is proposed that the 23 kDa protein is associated with a generalized water stress response mechanism and might play a role in water stress tolerance in seedlings.