Diurnal and circadian fluctuation of malate levels and its close relationship to nitrate reductase activity in tobacco leaves

Deng, Ming-De; Moureaux, Thérèse; Lamaze, Thierry

doi:10.1016/0168-9452(89)90065-4

Cited by 17 publications

(9 citation statements)

References 20 publications

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“…The synthesis of malate from phosphoenolpyruvate may be involved in the neutralization of OH" generated during nitrate reduction (Davies 1979). De Deng et al (1989) reported that increases in malate level and nitrate reductase activity during the day compared to the night in leaves of nitrate-fed Nicotiana tabacum L. plants persisted in constant light but not in constant darkness. In the present study glutamine and malate in xylem fluid were not well correlated, and the circadian rhythm continued in constant darkness, but not in continuous light.…”

Section: Discussionmentioning

confidence: 99%

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Andersen

Brodbeck

Mizell

1993

Physiologia Plantarum

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Diurnal variations in the concentrations of major organic compounds occurred in xylem fluid extracted from Lagerstroemia indica L. The concentration of amino acids and the N/C ratio was at a maximum and that of organic acids was at a minimum between 1230 and 2030 h. Since the concentrations of total organic nitrogen, total amino acids and most individual amino acids (but not organic acids or sugars) were also proportional to xylem tension two experiments were performed to discern whether variations in chemistry were a consequence of diurnal changes in moisture stress. In the first experiment, L. indica, exposed to variable levels of moisture stress during midday, manifested an increase in organic acids and a reduction in the N/C ratio. In the second experiment, chemical profiles of xylem fluid were collected and compared for plants exposed to a natural photoperiod, constant darkness or continuous light at noon and midnight. After 1 day amino acids increased in concentration during midday for all treatments; the variation was greatest (10‐fold) for plants in constant darkness where xylem tension varied from 0.20 to 0.25 MPa. Only plants exposed to continuous light lost a diurnal rhythm after 3 days. Thus, the circadian rhythm was endogenous, terminated in continuous light and was not mediated by changes in moisture stress. Glutamine accounted for most of the diurnal variation in total amino acids, organic nitrogen and the N/C ratio in xylem fluid.

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Section: Discussionmentioning

confidence: 99%

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Andersen

Brodbeck

Mizell

1993

Physiologia Plantarum

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“…The increase of the NIA transcript and NIA activity was antagonized by malate, and synthesized and exported via the phloem to the roots where it is decarboxylated (Raven 1986(Raven , 1988Martinoia & Rentsch 1994). During the day, nitrate assimilation and the accompanying synthesis of malate proceed more rapidly than malate export, and malate accumulates to high levels that are equivalent to 25-30% of the amount of assimilated nitrate (Touraine, Grignon & Grignon 1988;Deng, Moureaux & Lamaze 1989;Kaiser & Förster 1989;Scheible et al 1997b).…”

Section: Introductionmentioning

confidence: 99%

Influence of malate and 2-oxoglutarate on the NIA transcript level and nitrate reductase activity in tobacco leaves

Muller¹,

Scheible²,

Stitt³

et al. 2001

Plant Cell Environ

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slightly accelerated by 2-oxoglutarate. (iv) Plants were placed in the dark for 60 h to reduce NIA activity to the limit of detection, and leaf discs were then incubated in the dark on sucrose to achieve a photosynthesis-independent increase of NIA activity. This was strongly inhibited by malate. (v) It is concluded that malate inhibits NIA expression, affecting both the NIA transcript level and NIA activity. Although the results are consistent with a role for 2-oxoglutarate in the regulation of NIA expression, the impact is less marked and no endogenous changes of 2-oxoglutarate were found that are likely to have a significant effect on NIA expression.

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“…Organic acid metabolism has two different functions during nitrate assimilation. (i) Phosphoenolpyruvate carboxylase (PEPC) operates with malate dehydrogenase to provide malate, that acts as a counter‐anion and prevents alkalization during nitrate assimilation (Deng, Moreaux & Lamaze 1989; Martinoia & Rentsch 1994). The malate is exported to the roots, where it is decarboxylated (Martinoia & Rentsch 1994).…”

Section: Introductionmentioning

confidence: 99%

Reciprocal diurnal changes of phosphoenolpyruvate carboxylase expression and cytosolic pyruvate kinase, citrate synthase and NADP‐isocitrate dehydrogenase expression regulate organic acid metabolism during nitrate assimilation in tobacco leaves

Scheible

Krapp

Stitt

2000

Plant Cell & Environment

172

183

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expression of NR. Activity of all four enzymes decreased in nitrate-limited wild-type plants. (iv)In the light, malate accumulated, citrate decreased, and about 30% of the assimilated nitrate accumulated temporarily as glutamine, ammonium, glycine and serine. These changes were reversed during the night. (v) It is proposed that the diurnal changes of expression facilitate preferential synthesis of malate to act as a counter-anion for pH regulation during the first part of the light period when NR activity is high, and preferential synthesis of 2-oxoglutarate to act as a nitrogen acceptor later in the day when large amounts of nitrogen have accumulated in ammonium, glutamine and other amino acids including glycine in the photorespiration pathway, and NR activity has been decreased. Key INTRODUCTIONPhotosynthetic metabolism in source leaves is subject to dramatic diurnal changes (Geiger & Servaites 1994). The most obvious is the alternation between photosynthesis in the light and respiration in the dark. Superimposed is a cycle of starch accumulation and mobilization which allows part of the assimilated carbon to be temporarily stored in the leaf to support sucrose export during the night (Stitt, Huber & Kerr 1987;Heineke et al. 1994;Geiger & Servaites 1994). The balance between carbon export and accumulation even shifts during the light period, with the early part of the light period being characterized by high sucrose phosphate synthase (SPS, EC 2.4.1.14) activity (Stitt et al. 1987;Stitt 1996) and the later part by lower SPS activity and higher rates of starch synthesis (Stitt et al. 1987;Stitt 1996). Analogous diurnal changes occur in nitrogen metabolism. Nitrate reductase (NR) activity is highest in the first part of the light period, declines in the later part of the light period, and is low or negligible at night (Galangau et al.

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Diurnal and circadian fluctuation of malate levels and its close relationship to nitrate reductase activity in tobacco leaves

Cited by 17 publications

References 20 publications

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Influence of malate and 2-oxoglutarate on the NIA transcript level and nitrate reductase activity in tobacco leaves

Reciprocal diurnal changes of phosphoenolpyruvate carboxylase expression and cytosolic pyruvate kinase, citrate synthase and NADP‐isocitrate dehydrogenase expression regulate organic acid metabolism during nitrate assimilation in tobacco leaves

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