Metabolic regulation of the gene encoding glutamine-dependent asparagine synthetase in Arabidopsis thaliana

Hon Ming Lam, Sheila S Y Peng, Gloria M. Coruzzi

Research output: Contribution to journalArticle

Abstract

Here, we characterize a cDNA encoding a glutamine-dependent asparagine synthetase (ASN1) from Arabidopsis thaliana and assess the effects of metabolic regulation on ASNI mRNA levels. Sequence analysis shows that the predicted ASN1 peptide contains a purF-type glutamine-binding domain. Southern blot experiments and cDNA clone analysis suggest that ASN1 is the only gene encoding glutamine-dependent asparagine synthetase in A. thaliana. The ASN1 gene is expressed predominantly in shoot tissues, where light has a negative effect on its mRNA accumulation. This negative effect of light on ASN1 mRNA levels was shown to be mediated, at least in part, via the photoreceptor phytochrome. We also investigated whether light-induced changes in nitrogen to carbon ratios might exert a metabolic regulation of the ASN1 mRNA accumulation. These experiments demonstrated that the accumulation of ASN1 mRNA in dark-grown plants is strongly repressed by the presence of exogenous sucrose. Moreover, this sucrose repression of ASN1 expression can be partially rescued by supplementation with exogenous amino acids such as asparagine, glutamine, and glutamate. These findings suggest that the expression of the ASN1 gene is under the metabolic control of the nitrogen to carbon ratio in cells. This is consistent with the fact that asparagine, synthesized by the ASN1 gene product, is a favored compound for nitrogen storage and nitrogen transport in dark-grown plants. We have put forth a working model suggesting that when nitrogen to carbon ratios are high, the gene product of ASN1 functions to re-direct the flow of nitrogen into asparagine, which acts as a shunt for storage and/or long-distance transport of nitrogen.

Original languageEnglish (US)
Pages (from-to)1347-1357
Number of pages11
JournalPlant Physiology
Volume106
Issue number4
StatePublished - Dec 1994

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aspartate-ammonia ligase
glutamine
Arabidopsis thaliana
asparagine
nitrogen
genes
carbon
sucrose
nitrogen compounds
phytochrome
photoreceptors
glutamates
Southern blotting
sequence analysis
peptides
clones
gene expression
amino acids
shoots

ASJC Scopus subject areas

  • Plant Science

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Metabolic regulation of the gene encoding glutamine-dependent asparagine synthetase in Arabidopsis thaliana. / Lam, Hon Ming; Peng, Sheila S Y; Coruzzi, Gloria M.

In: Plant Physiology, Vol. 106, No. 4, 12.1994, p. 1347-1357.

Research output: Contribution to journalArticle

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