The regulatory PII protein controls arginine biosynthesis in Arabidopsis.
In higher plants, PII is a nuclear-encoded plastid protein which is homologous to bacterial PII signalling proteins known to be involved in the regulation of nitrogen metabolism. A reduced ornithine, citrulline and arginine accumulation was observed in two Arabidopsis PII knock-out mutants in response to NH4+ resupply after N starvation. This difference could be explained by the regulation of a key enzyme of the arginine biosynthesis pathway, N-acetyl glutamate kinase (NAGK) by PII. In vitro assays using purified recombinant proteins showed the catalytic activation of Arabidopsis NAGK by PII giving the first evidence of a physiological role of the PII protein in higher plants. Using Arabidopsis transcriptome microarray (CATMA) and RT-PCR analyses, it was found that none of the genes involved in the arginine biosynthetic or catabolic pathways were differentially expressed in a PII knock-out mutant background. In conclusion, the observed changes in metabolite levels can be explained by the reduced activation of NAGK by PII.
Ferrario-Méry
Sylvie
S
Unité de Nutrition Azotée des Plantes, Institut National de la Recherche Agronomique, INRA, Route de St. Cyr, 78026 Versailles Cedex, France. ferrario@versailles.inra.fr
Besin
Evelyne
E
Pichon
Olivier
O
Meyer
Christian
C
Hodges
Michael
M
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000302:isolation & purification / Q000378:metabolism*; D001120:Arginine / Q000096:biosynthesis*; D002262:Carboxy-Lyases / Q000235:genetics; D002956:Citrulline / Q000378:metabolism; D004789:Enzyme Activation; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D009154:Mutation / Q000235:genetics; D009952:Ornithine / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
D029681:Arabidopsis Proteins; D051922:PII Nitrogen Regulatory Proteins; C473074:PII protein, Arabidopsis; D012333:RNA, Messenger; D011994:Recombinant Proteins; D002956:Citrulline; D001120:Arginine; D009952:Ornithine; D017853:Phosphotransferases (Alcohol Group Acceptor); C018716:N-acetylglucosamine kinase; D002262:Carboxy-Lyases; C019722:arginine decarboxylase