GENE-EXPRESSION PATTERNS, AND UPTAKE AND FATE OF FED ABA IN WHITE SPRUCE SOMATIC EMBRYO TISSUES DURING MATURATION

Changes in cellular protein accumulation and in in vivo and in vitro p rotein synthesis, in somatic embryo tissues of white spruce during a 4 2 d maturation period were followed by two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (2-D SDS-PAGE), These inve stigations were complemented by an analysis of uptake and fate of fed abscisic acid (ABA) in somatic embryo tissues grown on maturation medi um, When Stage 1 somatic embryos were cultured on ABA-containing matur ation medium, many changes were observed in patterns of gene expressio n and in protein synthesis and accumulation which could be associated with embryo development, The polypeptides observed could be categorize d as constitutive, embryo-abundant, embryo maturation-related and embr yo stage-related, as well as those with non-specific changes, Accumula tion of label from fed H-3-(+)-ABA in embryo tissues reached a plateau 3 d after Stage 1 somatic embryos were placed on maturation medium, A BA taken into tissues was rapidly metabolized, and 40% of radioactivit y in tissues after 1 d of culture resulted from ABA metabolites, This value increased to 90% after 3 weeks culture, Conjugated ABA and oxidi zed ABA (phaseic acid and dihydrophaseic acid) were major forms of ABA metabolites in spruce embryo tissues, Using a single 42 d culture per iod following transfer to medium with ABA, the conditions that stimula te the sequence of developmental changes of somatic embryo maturation during the first 21 d do not reoccur during the second 21 d, Unless gr eater synchronization of Stage 1 cultures can be achieved, it is there fore unlikely that yields of mature somatic embryos will be increased by this method.