Arabidopsis chloroplasts dissimilate L-arginine and L-citrulline for use as N source.
When aseptically grown on defined medium with either L-arginine, L-citrulline, or nitrate as the sole N source, Arabidopsis plants grew and developed normally. Three catabolic activities, L-arginine iminohydrolase, L-ornithine carbamoyltransferase, and carbamate kinase, were found in stromal fractions of purified Arabidopsis chloroplasts. These activities dissimilate L-arginine and/or L-citrulline into L-ornithine, ammonium, bicarbonate, and ATP. In physiological tests with purified, intact Arabidopsis chloroplasts, L-[guanido-14C]arginine was rapidly taken up and about 10% was decomposed, releasing 14CO2. Therefore, chloroplasts can take up and dissimilate L-arginine. In principle, chloroplast arginine dissimilation allows Arabidopsis to use L-arginine and/or L-citrulline as general N sources for growth. However, plants rarely encounter exogenous L-arginine and/or L-citrulline in amounts exceeding their biosynthetic needs. Therefore, L-arginine and L-citrulline might serve as endogenous N sources.
Ludwig
R A
RA
Department of Biology, Sinsheimer Laboratories, University of California, Santa Cruz 95064.
D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism*; D001639:Bicarbonates / Q000378:metabolism; D002451:Cell Compartmentation; D002736:Chloroplasts / Q000378:metabolism*; D002956:Citrulline / Q000378:metabolism*; D006867:Hydrolases / Q000032:analysis; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009952:Ornithine / Q000378:metabolism; D009954:Ornithine Carbamoyltransferase / Q000032:analysis; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
D001639:Bicarbonates; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D002956:Citrulline; D000255:Adenosine Triphosphate; D001120:Arginine; D009952:Ornithine; D009954:Ornithine Carbamoyltransferase; D017851:Phosphotransferases (Carboxyl Group Acceptor); C019288:carbamate kinase; D006867:Hydrolases; C019723:arginine deiminase; D009584:Nitrogen