Salt-induced expression of NADP-dependent isocitrate dehydrogenase and ferredoxin-dependent glutamate synthase in Mesembryanthemum crystallinum.
NADP-specific isocitrate dehydrogenase is a key cytosolic enzyme that links C and N metabolism by supplying C skeletons for primary N assimilation in plants. We report the characterization of the transcript Mc-ICDH1 encoding an NADP-dependent isocitrate dehydrogenase (NADP-ICDH, EC 1.1.1.42) from the facultative halophyte Mesembryanthemum crystallinum L., focussing on salt-dependent regulation of the enzyme. The activity of NADP-ICDH in plants adapted to high salinity increased in leaves and decreased in roots. By transcript analyses and Western-type hybridizations, expression of Mc-ICDH1 was found to be stimulated in leaves in salt-adapted M. crystallinum. By immunocytological analyses, NADP-ICDH proteins were localized to most cell types with strongest expression in epidermal cells and in the vascular tissue. In leaves of salt-adapted plants, signal intensities increased in mesophyll cells. In contrast to Mc-ICDH1, the activity and transcript abundance of ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1.4.7.1), which is the key enzyme of N assimilation and biosynthesis of amino acids, decreased in leaves in response to salt stress. The physiological roles of NADP-ICDH and Fd-GOGAT in the adaptation of plants to high salinity are discussed.
D000222:Adaptation, Physiological / Q000187:drug effects; D000594:Amino Acid Oxidoreductases / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D002244:Carbon / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007150:Immunohistochemistry; D007521:Isocitrate Dehydrogenase / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D035723:Mesembryanthemum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology*
D012965:Sodium Chloride; D002244:Carbon; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+); D000594:Amino Acid Oxidoreductases; C042233:glutamate synthase (ferredoxin); D009584:Nitrogen