Abstract
The growth, freezing tolerance and two-dimensional protein profiles of bromegrass ( Bromus inermis Leyss) cell cultures were investigated following repeated exposure to 75 μM abscisic acid (ABA) for 5 weeks. Following prolonged (36 d) exposure to ABA, freezing tolerance was enhanced and fresh-mass gain was reduced compared to a 10-d ABA treatment. Also, fifteen additional ABA-responsive proteins were detected after 5 weeks of ABA treatment that were not detected in cells treated for 10 d. In addition, intensity changes occurred in several ABA-responsive proteins that were detected after 10-d incubation periods. Two polypeptides (26 and 29 kD) initially responsive to ABA decreased over 5 weeks of treatment. Transfer of ABA-treated cells to culture media lacking ABA for 14 d resulted in a 22°C decrease in freezing tolerance and increased growth, but there was no detectable change in the ABA-responsive polypeptides. Abscisic acid treatment at 3°C increased freezing tolerance at an accelerated rate and to a greater level than 3°C alone, but less so than ABA treatments at 25°C. However, the same ABA-responsive polypeptides detected at 25°C were present in cells treated with ABA at 3°C. These observations suggest that synthesis and accumulation of ABA-responsive polypeptides are only one component involved in freezing tolerance and other factors must be involved.
Published Version
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