Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Overnight low-temperature exposure inhibits photosynthesis in chilling-sensitive species, such as tomato and cucumber, by as much as 60%. Earlier work showed that low temperature stalled the endogenous rhythm controlling transcription of certain nuclear-encoded genes in chilling-sensitive plants causing the synthesis of the corresponding transcripts and proteins to be mistimed upon rewarming. The activity of nitrate reductase (NR), the first and rate-limiting step in the assimilation of nitrate into amino acids in leaves, is subjected to a varied range of regulatory influences including a robust circadian rhythm. We show here that although NR regulation is disrupted by low temperatures, the change is transient and does not alter the phase of the NR endogenous rhythm following the chill. There is a temporary induction of de novo transcription of NR causing an increase in both NR protein and activity. This occurs regardless of the time in the circadian cycle that the chilling episode is initiated thereby decoupling the normally closely coordinated processes of carbon and nitrogen assimilation. This decoupling would be expected to deplete cellular reductant and carbon skeleton reserves as well as allow accumulation of cytotoxic intermediates of nitrogen assimilation thereby contributing to the low temperature induced disruption of metabolism that takes place in photosynthetic cells of chilling sensitive plant species.
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PMID:Low temperature induces expression of nitrate reductase in tomato that temporarily overrides circadian regulation of activity. 1622 27

Chilling triggers rapid molecular responses that permit the maintenance of plant cell homeostasis and plant adaptation. Recent data showed that nitric oxide (NO) is involved in plant acclimation and tolerance to cold. The participation of NO in the early transduction of the cold signal in Arabidopsis thaliana was investigated. The production of NO after a short exposure to cold was assessed using the NO-sensitive fluorescent probe 4, 5-diamino fluoresceine diacetate and chemiluminescence. Pharmacological and genetic approaches were used to analyze NO sources and NO-mediated changes in cold-regulated gene expression, phosphatidic acid (PtdOH) synthesis and sphingolipid phosphorylation. NO production was detected after 1-4h of chilling. It was impaired in the nia1nia2 nitrate reductase mutant. Moreover, NO accumulation was not observed in H7 plants overexpressing the A. thaliana nonsymbiotic hemoglobin Arabidopsis haemoglobin 1 (AHb1). Cold-regulated gene expression was affected in nia1nia2 and H7 plants. The synthesis of PtdOH upon chilling was not modified by NO depletion. By contrast, the formation of phytosphingosine phosphate and ceramide phosphate, two phosphorylated sphingolipids that are transiently synthesized upon chilling, was negatively regulated by NO. Taken together, these data suggest a new function for NO as an intermediate in gene regulation and lipid-based signaling during cold transduction.
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PMID:Nitric oxide participates in cold-responsive phosphosphingolipid formation and gene expression in Arabidopsis thaliana. 2117 30