Arabidopsis thaliana ASN2 encoding asparagine synthetase is involved in the control of nitrogen assimilation and export during vegetative growth

Laure Gaufichon, Céline Masclaux-Daubresse, Guillaume Tcherkez, Michèle Reisdorf-Cren, Yukiko Sakakibara, Toshiharu Hase, Gilles Clément, Jean Christophe Avice, Olivier Grandjean, Anne Marmagne, Stéphanie Boutet-Mercey, Marianne Azzopardi, Fabienne Soulay, Akira Suzuki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

71 Citations (Scopus)

Abstract

We investigated the function of ASN2, one of the three genes encoding asparagine synthetase (EC 6.3.5.4), which is the most highly expressed in vegetative leaves of Arabidopsis thaliana. Expression of ASN2 and parallel higher asparagine content in darkness suggest that leaf metabolism involves ASN2 for asparagine synthesis. In asn2-1 knockout and asn2-2 knockdown lines, ASN2 disruption caused a defective growth phenotype and ammonium accumulation. The asn2 mutant leaves displayed a depleted asparagine and an accumulation of alanine, GABA, pyruvate and fumarate, indicating an alanine formation from pyruvate through the GABA shunt to consume excess ammonium in the absence of asparagine synthesis. By contrast, asparagine did not contribute to photorespiratory nitrogen recycle as photosynthetic net CO2 assimilation was not significantly different between lines under both 21 and 2% O2. ASN2 was found in phloem companion cells by in situ hybridization and immunolocalization. Moreover, lack of asparagine in asn2 phloem sap and lowered 15N flux to sinks, accompanied by the delayed yellowing (senescence) of asn2 leaves, in the absence of asparagine support a specific role of asparagine in phloem loading and nitrogen reallocation. We conclude that ASN2 is essential for nitrogen assimilation, distribution and remobilization (via the phloem) within the plant.

Original languageEnglish
Pages (from-to)328-342
Number of pages15
JournalPlant, Cell and Environment
Volume36
Issue number2
DOIs
Publication statusPublished - Feb 2013
Externally publishedYes

Fingerprint

Dive into the research topics of 'Arabidopsis thaliana ASN2 encoding asparagine synthetase is involved in the control of nitrogen assimilation and export during vegetative growth'. Together they form a unique fingerprint.

Cite this