EFFECT OF ABSCISIC ACID, OSMOTICUM AND DESICCATION ON 11S STORAGE PROTEIN GENE EXPRESSION IN SOMATIC EMBRYOS OF WHITE SPRUCE

摘要

The effect of ABA, non-permeating osmoticum and late stage maturation drying on 11S storage protein gene expression in white spruce somatic embryos was investigated. A partial cDNA clone encoding the beta-polypeptide of white spruce 11S legumin-like seed storage protein (named beta-coniferin) was employed as a probe. Northern blot analyses demonstrated that in somatic embryos matured with 16 mu M ABA and 7.5% PEG, the levels and patterns of accumulation of transcripts during early and mid-stages of embryogenesis were comparable to those observed in zygotic embryos at a similar morphological stage. Steady-state levels of coniferin transcripts declined when late stage somatic embryos were exposed to a desiccation treatment. Levels of coniferin transcripts in somatic embryos matured with 16 mu M ABA and low osmoticum were substantially lower than those of somatic embryos matured with 7.5% PEG and 16 mu M ABA. Increasing concentrations of ABA resulted in higher levels of accumulation of coniferin transcripts, however, the levels in somatic embryos matured with 32 mu M ABA and low osmoticum remained lower than those of somatic embryos matured on 16 mu M and 7.5% PEG indicating that the latter treatment is optimum for induction and accumulation of coniferin transcripts. The similarity of 11S storage protein gene expression in somatic embryos with zygotic embryos, along with their sensitivity to ABA and osmoticum indicates that somatic embryos may provide a useful system to facilitate studies of gene regulation in conifers. [References: 30]