INDUCTION OF FREEZING TOLERANCE IN POTATO (SOLANUM-COMMERSONII) SUSPENSION CULTURED-CELLS

The induction of freezing tolerance by abscisic acid (ABA) or cold treatment in suspension cultured cells of Solanum commersonii was studied. Both ABA (50-100-mu-M) at 23-degrees-C and low temperature (4-degrees-C) increased freezing tolerance in cultured Solanum commersonii cells from a LJ50 (freezing temperature at which 50% cells were killed) of -5-degrees-C (control) to -11.5-degrees-C in 2 days. Cold-induced freezing tolerance reached its maximum at 2 days and remained constant throughout the cold acclimation period of 11 days. The freezing tolerance induced by ABA, however, showed a rapid decline 2 to 5 days after initiation of ABA treatments. Addition of ABA (100-mu-M) to the culture medium at the inception of low temperature treatment did not enhance freezing tolerance of the cells beyond the level attainable by either treatment singly. Poly(A+)-RNA was isolated from the respective treatments, translated in a rabbit reticulocyte lysate cell free system, and the translation products were resolved by two dimensional polyacrylamide gel electrophoresis (2D-PAGE). Analysis of the in vitro translated products revealed changes in the abundance of approximately 26 products (encoding for polypeptides with M(r) of 14 to 69 kDa and pI of 4.90 to G.60) in ABA-treated cells 12 h after treatment, and 20 (encoding for polypeptides with M(r) of 12 to 69 kDa, with pI of 4.80 to 6.42) in cells exposed to 4-degrees-C for 12 h. There were only 5 novel translation products observed when the ABA-treated cells reached the highest level of freezing tolerance (2 days after the initiation of ABA treatment). Changes in translatable RNA populations during the induction of freezing tolerance in cells treated with either ABA or low temperature are discussed.