azaserine and tungstate

Although an accumulating amount of research clearly indicates that plants are capable of taking up exogenous amino acids, the actual importance of such organic N sources for plant N nutrition is under debate. In this study, we show that amino acid uptake by Scots pine (Pinus sylvestris L.) is significantly decreased by elevated internal NH(4)(+) levels, while it increases following exposure to exogenous amino acids. Furthermore, amino acid uptake is larger in N-deficient plants than in plants grown with a large access of N. The regulatory pattern of amino acid uptake shows important similarities to the regulation of NO(3)(-) and NH(4)(+) transport as well as to the regulation of yeast amino acid transporters. In addition, our data suggest that uptake may be regulated by factors not originating from N metabolism. The up-regulation of uptake in response to N deficiency suggests that amino acid uptake may be a significant contributor to the N economy of P. sylvestris.

Topics: Adaptation, Physiological; Amino Acids; Aminooxyacetic Acid; Azaserine; Enzyme Inhibitors; Glutamate Synthase; Glutamate-Ammonia Ligase; Glutamic Acid; Glutamine; Methionine Sulfoximine; Nitrate Reductase; Nitrate Reductases; Nitrates; Nitrogen; Plant Roots; Quaternary Ammonium Compounds; Tracheophyta; Transaminases; Tungsten Compounds; Up-Regulation