Changes in the activities of ferredoxin- and NADH-glutamate synthase during seedling development of peas

Abstract

Ferredoxin-glutamate synthase (EC 1.4.7.1) and NADH-glutamate synthase (EC 1.4.1.14) activities in pea seedlings (Pisum sativum L., cv. Alaska) were measured during germination and the early stages of growth. Both enzymes were detected at all stages in the developing roots and shoots, but their relative activities varied according to the growth stages. In shoots of 5-d-old seedlings, the ratio of the NADH-enzyme to the ferredoxin-enzyme was 72:28. However, the ferredoxin-activity increased rapidly and in shoots of 17-d-old seedlings, the activities were in the ratio of 3:97. Similar trends in these ratio changes were observed in the roots. In both tissues, the NADH-enzyme was shown to be predominant in the immature parts. When chloroplasts prepared from mature pea leaves were incubated with [(14)C]glutamine and 2-oxoglutarate, the production of [(14)C]glutamate was found to be light dependent and was inhibited by azaserine (3 mM) and 3-(3,4-dichlorophenyl)-1-1-dimethylurea (20 μM). In contrast, considerable amounts of [(14)C]glutamate were formed by chloroplasts from young leaves even in the dark. Addition of malate or dihydroxyacetone phosphate to the reaction mixture resulted in a twofold increase of this dark- and azaserine-sensitive [(14)C]glutamate formation.

Structure and Regulation of Ferredoxin‐Dependent Glutamase Synthase from Arabidopsis Thaliana

“…Fddependent glutamate synthase is also present in non-photosynthetic roots (Miflin and Lea, 1975;Suzuki et al, 1985) and N,-fixing legume root nodules (Suzuki et al, 1984;Chen and Cullimore, 1988;Gregerson et al, 1993), where its physiological functions are unknown. NADH-dependent glutamate synthase, which is probably located in the plastid (Emes and Fowler, 1979;Suzuki et al, 1981), occurs predominantly in non-photosynthetic shoots (Matoh et al, 1982;Wallsgrove et al, 1982), roots (Miflin and Lea, 1975) and root nodules (Chen and Cullimore, 1988; Gregerson et al, 1993). It could account for the assimilation of non-photorespiratory ammonia (Somerville and Ogren, 1980).…”

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice

“…NADH-GOGAT and GS were determined according to Matoh and Takahashi (1982) and O'Neal and Joy (1973), respectively.…”

Abiotic Stress Generates ROS That Signal Expression of Anionic Glutamate Dehydrogenases to Form Glutamate for Proline Synthesis in Tobacco and Grapevine

“…In vitro activity of NADH-GOGAT was assayed using NADH as the electron donor by determining the formation of Glu in the reaction as described by Matoh and Takahashi (1982). One unit of enzyme activity was defined as the amount catalyzing the formation of 1.0 mmol of Glu per minute at 308C.…”