title: GCN2-dependent phosphorylation of eukaryotic translation initiation factor-2alpha in Arabidopsis.
abstract: 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 eIF2alpha (AteIF2alpha) 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 AteIF2alpha 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 AteIF2alpha was not phosphorylated.
authors.affiliation: Centre for Crop Genetic Improvement, Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yifei
authors.initials: Y
authors.lastname: Wang
authors.forename: Kostya
authors.initials: K
authors.lastname: Kanyuka
authors.forename: Martin A J
authors.initials: MA
authors.lastname: Parry
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Powers
authors.forename: Nigel G
authors.initials: NG
authors.lastname: Halford
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000096:biosynthesis*; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000187:drug effects; D019184:Carmovirus / Q000502:physiology; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006540:Herbicides / Q000494:pharmacology; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D009154:Mutation; D009566:Nitrates / Q000378:metabolism; D010766:Phosphorylation; D010935:Plant Diseases / Q000276:immunology / Q000821:virology; D011494:Protein Kinases / Q000378:metabolism*; D036226:Seedlings / Q000201:enzymology; D017806:Tymovirus / Q000502:physiology
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D015852:Eukaryotic Initiation Factor-2; D006540:Herbicides; D009566:Nitrates; D011494:Protein Kinases; C480318:GCN2 protein, Arabidopsis