Dry artificial seeds through induction of desiccation tolerance of somatic embryos by abscisic acid and study of mechanism of the desiccation tolerance

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Artificial seed technology may provide potential benefits in plant propagation systems. If somatic embryos could maintain their viability after their water content was decreased to the level of true seeds, they were used as a method of germplasm storage and a model system of study of developmental plant biology as well as a utilization of artificial seed. The objective of this study was to investigate induction of desiccation tolerance in microspore-derived embryos of Brassica crops by exogenous application of ABA and to analyze the proteins and genes of the desiccation tolerant embryos.After desiccation treatment, the relative water content of embryos had decreased to about 10%. Desiccation tolerance of the embryos was induced by ABA. These phenomena were influenced by the size of embryos and the concentration of ABA, but not dependent on genotypes. The frequency of plant conversion of dry cotyledonary embryos which were treated with 10^<-4>-10^<-5>M ABA was 41-53%. In contrast, almos … More t all embryos lost their viability after desiccation, when they were not treated with ABA. Globular embryos could not acquire desiccation tolerance, even if they were treated with ABA. Though desiccation tolerance of the embryos was also induced by high osmoticum, the frequency of plant conversion (1.3-8.3%) was lower than that treated with ABA. The dry embryos maintained their plant conversion ability after six months of storage under room temperature conditions. The plantlets recovered from dry embryos were not morphologically different from those from non-desiccated ones.SDS-PAGE and western blot analysis of proteins revealed that the embryos treated with ABA accumulated seed storage proteins. And two dimensional gel analysis of the embryo proteins indicated that several new polypeptides were synthesized during ABA treatment and they may be associated with the acquisition of desiccation tolerance. A cDNA library representing mRNA's present in embryos treated with ABA was screened using Lea gene (pLEA76) as a probe. Six cDNA clones were selected. Now we are characterizing these cDNA clones. Less