INDUCED GENE-EXPRESSION FOLLOWING ABA UPTAKE IN EMBRYOGENIC SUSPENSION-CULTURES OF PICEA-GLAUCA

White spruce (Picea glauca) embryogenic suspension cultures were used to investigate early events in abscisic acid (ABA) stimulation of embr yo maturation, specifically ABA uptake and altered gene expression. AB A uptake by the embryogenic tissues was by diffusion. Fed H-3-(+)-ABA accumulated in tissues linearly during the first hour acid reached a p lateau at around 2 h. When suspension cultures were fed with increasin g concentrations of H-3-(+)-ABA, between 0 and 200 mu M, a linear incr ease in ABA content was observed. The metabolites of H-3-(+)-ABA in ti ssues could be detected in the first hour of incubation with ABA, at w hich time 8% of the total radioactivity was attributable to ABA metabo lites; this value increased to about 10% after 24 h incubation. At thi s time polar ABA compounds which include conjugated forms, and oxidize d ABA compounds (phaseic acid and dihydrophaseic acid) were the major metabolites in white spruce suspension tissues. Protein synthesis in s uspension-cultured tissue, either treated with (+)-ABA or untreated, w as analyzed by separating in vivo-labelled and in vitro-translated pol ypeptides by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2-D SDS-PAGE). ABA-induced changes in gene expressio n and protein synthesis were detectable by 6 h after exposure to ABA. These changes continued throughout the 24 h incubation period, and inc luded the synthesis of new polypeptides, and altered level of polypept ides represented also in untreated cells.