ABSCISIC ACID-INDUCED SECRETION OF AN ANTIFREEZE-LIKE PROTEIN IN EMBRYOGENIC-CELL LINES OF PICEA-ABIES

Embryogenic cell lines of Picea abies have been divided into two group s, A and B, based on the morphology and physiology of the somatic embr yos. The differences between these cell lines can be related to the pa tterns of extracellular proteins. Group A and B embryos respond differ ently to abscisic acid (ABA) for maturation and transient expression o f ABA-induced promoter (Dc8) after bombardment. The aim of the study w as to compare changes in synthesis and secretion of proteins after an ABA treatment of embryogenic cultures of Picea abies differing in thei r ability to respond to ABA. A BA was observed to induce as well as de crease synthesis and/or secretion of several proteins. Some of these c hanges were found in individual cell lines whereas others were charact eristic for all cell lines within a group. Group B cell lines produced 64 and 42 kDa cellular proteins and most of group A cell lines produc ed an 88 kDa protein in response to ABA. Two extracellular proteins we re found to be specifically secreted after ABA treatment; a 70 kDa pro tein was secreted by A-group cell lines and an 80 kDa protein by B-gro up cell lines. The N-terminal amino acid sequence of the 70 kDa protei n showed 40 % identity over 20 amino acids to antifreeze proteins isol ated from serum of several species of polar water fish. The possible r oles of this protein in freezing resistance are discussed. Freezing to lerance differed between group A and B cultures. Group A cell lines ty pically survived down to -15 degrees C while those belonging to group B did not survive lower than -10 degrees C. The ABA treatment confers freezing resistance in group B cell lines but not in group A.