REGULATION OF ALPHA-AMYLASE ISOENZYME EXPRESSION IN ARAUCARIA-ARAUCANA BY GIBBERELLIC AND ABSCISIC ACIDS

Expression of alpha-amylase (EC 3.2.1.1) isoenzymes present in the emb ryos and mega-gametophytes of Araucaria araucana seedlings was studied under gibberellic acid (GA(3)) and abscisic acid (ABA) treatments and after 90 hr of imbibition in 20 mM of beta-chloroethyltrimethylammoni um (CCC), a GA(3) biosynthesis inhibitor. When CCC was used, alpha-amy lase activity in the treated embryos decreased to 28% with respect to the controls. The isoenzymes of R(m) 0.42 and 0.51 were greatly affect ed. When the embryos were imbibed simultaneously in the presence of 20 mM CCC and 10(-5) M of GA(3), alpha-amylase activity and the expressi on of isoenzymes were restored with respect to controls. ABA at 10(-4) and 10(-5) M decreased alpha-amylase activity of embryos to 67 and 81 %, respectively. Expression of isoenzymes of R(m) 0.51 was greatly dec reased by ABA but the effect on the others was small. Isoenzyme expres sion of mega-gametophytic alpha-amylase was not affected by CCC, GA(3) or ABA treatment. Copyright (C) 1997 Elsevier Science Ltd.