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JXB Advance Access published online on July 4, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern169
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

GCN2-dependent phosphorylation of eukaryotic translation initiation factor-2{alpha} in Arabidopsis

Yuhua Zhang1, Yifei Wang1 *, Kostya Kanyuka2, Martin A. J. Parry1, Stephen J. Powers3 and Nigel G. Halford1,{dagger}

1Centre for Crop Genetic Improvement, Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
2Centre for Sustainable Pest and Disease Management, Plant Pathology and Microbiology Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
3Centre for Mathematical and Computational Biology, Biomathematics and Bioinformatics Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK

{dagger} To whom correspondence should be addressed. E-mail: nigel.halford{at}bbsrc.ac.uk

The yeast regulatory protein kinase, general control non-derepressible-2 (GCN2) plays a key role in general amino acid control. GCN2 phosphorylates the {alpha} subunit of the trimeric eukaryotic translation initiation factor-2 (eIF2), bringing about a decrease in the general rate of protein synthesis but an increase in the synthesis of GCN4, a transcription factor that promotes the expression of genes encoding enzymes for amino acid biosynthesis. The present study concerned the phosphorylation of Arabidopsis eIF2{alpha} (AteIF2{alpha}) by the Arabidopsis homologue of GCN2, AtGCN2, and the role of AtGCN2 in regulating genes encoding enzymes of amino acid biosynthesis and responding to virus infection. A null mutant for AtGCN2 called GT8359 was obtained and western analysis confirmed that it lacked AtGCN2 protein. GT8359 was more sensitive than wild-type Arabidopsis to herbicides that affect amino acid biosynthesis. Phosphorylation of AteIF2{alpha} occurred in response to herbicide treatment but only in wild-type Arabidopsis, not GT8359, showing it to be AtGCN2-dependent. Expression analysis of genes encoding key enzymes for amino acid biosynthesis and nitrate assimilation revealed little effect of loss of AtGCN2 function in GT8359 except that expression of a nitrate reductase gene, NIA1, was decreased. Analysis of wild-type and GT8359 plants infected with Turnip yellow mosaic virus or Turnip crinkle virus showed that AteIF2{alpha} was not phosphorylated.

Key words: Amino acid signalling, general control non-derepressible, metabolic regulation, phosphorylation, protein kinase, virus infection

* Present address: Biotechnology Research Institute, Shanghai Academy of Agricultural Sciences, 2901 Bei Di Road, Shanghai 201106, Peoples Republic of China.

Received 17 April 2008; Revised 20 May 2008 Accepted 20 May 2008


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