Protein Synthesis in Bromegrass (<i>Bromus inermis</i> Leyss) Cultured Cells during the Induction of Frost Tolerance by Abscisic Acid or Low Temperature

Abstract

Bromus inermis Leyss cell cultures treated with 75 micromolar abscisic acid (ABA) at both 23 and 3 degrees C developed more freezing resistance than cells cultured at 3 degrees C. Protein synthesis in cells induced to become freezing tolerant by ABA and low temperature was monitored by [(14)C]leucine incorporation. Protein synthesis continued at 3 degrees C, but net cell growth was stopped. Most of the major proteins detected at 23 degrees C were synthesized at 3 degrees C. However, some proteins were synthesized only at low temperatures, whereas others were inhibited. ABA showed similar effects on protein synthesis at both 23 and 3 degrees C. Comparative electrophoretic analysis of [(14)C]leucine labeled protein detected the synthesis of 19, 21 and 47 kilodalton proteins in less than 8 hours after exposure to exogenous ABA. Proteins in the 20 kilodalton range were also synthesized at 3 degrees C. In addition, a 31 kilodalton protein band showed increased expression in freezing resistant ABA treated cultures after 36 hours growth at both 3 and 23 degrees C. Quantitative analysis of [(14)C]leucine labeled polypeptides in two-dimensional gels confirmed the increased expression of the 31 kilodalton protein. Two-dimensional analysis also resolved a 72 kilodalton protein enriched in ABA treated cultures and identified three proteins (24.5, 47, and 48 kilodaltons) induced by low temperature growth.