Accumulation of 19-kDa Plasma Membrane Polypeptide during Induction of Freezing Tolerance in Wheat Suspension-Cultured Cells by Abscisic Acid

Suspension-cultured cells derived from immature embryos of winterwheat (Triticum aestivum L. cv. Chihoku) were used in experimentsdesigned to obtain clues to the mechanism of the ABA-induceddevelopment of freezing tolerance. Cultured cells treated with50 µM ABA for 5 d at 23°C acquired the maximum levelof freezing tolerance (LT50; -21.6°C). The increased freezingtolerance of ABA-treated cells was closely associated with theremarkable accumulation of 19-kDa polypeptides in the plasmamembrane. The 19-kDa polypeptide components were isolated bypreparative gel electrophoresis and were further separated intoone major (AWPM-19) and other minor polypeptide components byTricine-SDS-PAGE. N-terminal ami no acid sequence of AWPM-19was determined, and a cDNA clone encoding AWPM-19 was isolatedby PCR from the library prepared from the ABA-treated culturedcells. The cDNA clone (WPM-J) encoded a 18.9 kDa hydrophobicpolypeptide with four putative membrane spanning domains andwith a high pi value (10.2). Expression of WPM-1 mRNA was dramaticallyinduced by 50 µM ABA within a few hours. These resultssuggest that the AWPM-19 might be closely associated with theABA-induced increase in freezing tolerance in wheat culturedcells. (Received January 20, 1997; Accepted March 31, 1997)