Enzymological study on inorganic nitrogen assimilation during redifferentiation of moss cells

近年来，我们已经建立了苔藓的悬浮细胞培养，其中包括：BarBula unguulata(Takio et al，1986)、Sphagnum imbricatum(Kajita et al.和Hedwigia ciliata(Takami和Takio 1987)，苔类植物Marchantia pareacea var.双翅目(Takio et al.1988)、贝氏异丝藻(Heteroscyphus Beschesellei)(Takami和Takio 1987)和角藻(Anthoceros Pot Tatus)(Takami et al.(1988年)。与高等植物的培养细胞不同，大多数苔藓植物的细胞不能在以硝酸盐为唯一氮源的培养基中生长，而它们的亲本或再分化的植物可以在这种培养基中生长。为了阐明分化与氮代谢的关系，测定了覆膜草细胞再分化为完整植株过程中氮同化酶的体外活性，并对悬浮培养的覆膜草细胞提取液中的硝酸还原酶(NAR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)和谷氨酸脱氢酶(GDH)的活性进行了测定。覆膜藻细胞产生的GDH具有不同于其他植物细胞的吡啶核苷酸专一性和适宜的pH。通过测定愈伤组织细胞和再生植株提取液中NAR、GOGAT和GOGAT的活性，确定了它们的催化活性。两种提取物的GS、GOGAT活性无明显差异。在愈伤组织细胞提取液中检测到较高的GDH活性，而在植株提取液中未检测到活性。

In recent years, we have established cell suspension cultures from the mosses, Barbula Unguiculata (Takio et al, 1986), Sphagnum imbricatum (Kajita et al. 1987) and Hedwigia ciliata (Takami and Takio 1987), the liverworts, Marchantia paleacea var. diptera (Takio et al. 1988) and Heteroscyphus beschesellei (Takami and Takio 1987), and the hornwort, Anthoceros punctatus (Takami et al. 1988). In contrast to cultures cells from higher plants, cell of most bryophyte species could not grow in a medium containing nitrate as the sole nitrogen source, while their parental or redifferentiated plants could grow in this medium. In order to elucidate the relatioship between differentiation and nitrogen metabolism, in vitro activities of nitrogen assimilating enzymes were determined during redifferentiation of S. imbricatum cells into whole plants.Appropriste conditions for measuring the activities of nitrate reductase (NaR), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) were determined in extraxts from suspension cultured cells of S. imbricatum. Pyridine nucleotide specificity and appropriate pH of GDH from S. imbricatum cells were different from those of other plant species. Catalytic properties of NaR, GS and GOGAT from S. imbricatum were similar to those from other plants.Activities of GS, GOGAT and GDH were determined in extracts from callus cells and redifferentiated plantlets. There was no difference in activities of GS, GOGAT between both extracts. High activity of GDH was detected in extracts from callus cells, while no activity was observed in that from plantlets.