During development on hormone-free media, somatic embryos pass through distinct morphological stages that superficially resemble those of zygotic embryo development (globular, heart, torpedo, cotyledonary stages). Despite these similarities, they differ from zygotic embryos in the extent of cotyledonary development and the patterns of synthesis and quantitative expression of seed-specific storage proteins (7S, 11S, and 2S proteins). Alfin (7S) is the first storage protein synthesized in developing zygotic embryos (stage IV). The 11S (medicagin) and 2S (Low Molecular Weight, LMW) storage proteins are not detectable until the following stage of development (stage V), although all three are present before the completion of embryo enlargement. Likewise, the 7S storage protein is the first to be synthesized in developing somatic embryos (day 5). Medicagin is evident by day 7 and the LMW protein by day 10. In contrast to zygotic embryos, alfin remains the predominant storage protein in somatic embryos throughout development. Not only are the relative amounts of medicagin and the LMW protein reduced in somatic embryos but the LMW protein is accumulated much later than the other proteins. Quantification of the storage protein mRNAs (7S, 11S, and 2S) by northern blot analysis confirms that there are substantial differences in the patterns of message accumulation in zygotic and somatic embryos of alfalfa (Medicago sativa). In zygotic embryos, the 7S, 11S, and 2S storage protein mRNAs are abundant during maturation and, in particular, during the stages of maximum protein synthesis (alfin, stages VI and VII; medicagin, stage VII; LMW, stage VII). In somatic embryos, the predominance of the 7S storage protein is correlated with increased accumulation of its mRNA, whereas the limited synthesis of the 11S storage protein is associated with much lower steady-state levels of its message. The mRNA for the LMW protein is present already by 3 days after transfer to hormone-free media, yet that protein is not evident on stained gels until day 10. Thus, both transcriptional and posttranscriptional events appear to be important in determining the protein complement of these seed tissues. On the basis of storage protein and mRNA accumulation, mature (14 days) somatic embryos most closely resemble stage VI zygotic embryos. The results of the developmental comparison also suggest that the patterns of synthesis of the individual storage proteins (7S, 11S, or 2S) are regulated independently of each other during embryogenesis in alfalfa.

To our knowledge the results provide the first direct demonstration of the toxic effects of oxalate in HK-2 cells, a line of human renal epithelial cells, and suggest that hyperoxaluria may contribute to renal tubular damage associated with calcium oxalate stone disease.

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Abstract.Proteins that have homology with dehydrins have been identified immunologically in the desiccationsensitive (recalcitrant) seeds of English oak (Quercus robur L.), European chestnut (Castanea sativa L.), horse chestnut (Aesculus hippocastanum L.), sycamore (Acer psuedoplatanus L.) and silver maple (Acer saccharinum L.), and in the desiccation-tolerant seeds of Norway maple (Acer platanoides L.). The mRNA for a late embryogenesis abundant (LEA) protein (dehydrin) was also detected by Northern blotting, using a cDNA clone (D11) from cotton embryos, in the recalcitrant and orthodox seeds. Medium-stringency washing was required to detect this hybridization. In Q. robur the amount of dehydrin protein increased during seed development, and LEA mRNA was induced by limited desiccation and by abscisic acid. Confirmation of the presence of dehydrin mRNA in mature Q. robur and C. sativa seeds was obtained by in-vitro translation of the extracted polyadenylated RNA followed by analysis of the immunoprecipitation products. Thus the presence of dehydrin proteins is not sufficient to confer desiccation tolerance on truly recalcitrant seeds, nor can their presence or absence be used as clear criteria for identification of recalcitrant seeds.