EXPRESSION OF ABUNDANT MESSENGER-RNAS DURING SOMATIC EMBRYOGENESIS OFWHITE SPRUCE [PICEA-GLAUCA (MOENCH) VOSS]

Embryogenic tissues of white spruce [Picea glauca (Moench) Voss] remai n in an early developmental stage while cultured on 2,4-dichlorophenox yacetic acid and N-6-benzyladenine, but develop to cotyledonary embryo s when these phytohormones are replaced by abscisic acid. Twenty-eight cDNAs were isolated from cotyledonary embryos by differential screeni ng against immature embryo and non-embryonic tissues. Temporal express ion patterns of these cDNAs during ABA-stimulated somatic embryo devel opment were observed. This showed that clones could be allocated to va rious groups, including embryo-abundant, embryo-maturation-induced, an d those whose expression was modulated during embryo development, germ ination or in non-embryogenic tissues. Expression corresponding to the se cDNA clones showed that there were various responses to exogenous A BA or polyethylene glycol during a period of 48 h. Analyses of DNA and predicted amino acid sequence revealed that 12 of 28 cDNA clones had no known homologues, while others were predicted to encode different l ate-embryogenesis-abundant proteins, early methionine-labelled protein s, storage proteins, heat-shock proteins, glycine-rich cell wall prote in, metallothionein-like protein and some other metabolic enzymes.