Pathways of Nitrogen Assimilation in Cowpea Nodules Studied using 15N2 and Allopurinol 1
AUTOR(ES)
Atkins, Craig A.
RESUMO
In the presence of 0.5 millimolar allopurinol (4-hydroxypyrazolo [3,4-d]pyrimidine), an inhibitor of NAD:xanthine oxidoreductase (EC 1.2.3.2), intact attached nodules of cowpea (Vigna unguiculata L. Walp. cv Vita 3) formed [15N]xanthine from 15N2 at rates equivalent to those of ureide synthesis, confirming the direct assimilation of fixed nitrogen into purines. Xanthine accumulated in nodules and was exported in increasing amounts in xylem of allopurinol-treated plants. Other intermediates of purine oxidation, de novo purine synthesis, and ammonia assimilation did not increase and, over the time course of experiments (4 hours), allopurinol had no effect on nitrogenase (EC 1.7.99.2) activity. Negligible 15N-labeling of asparagine from 15N2 was observed, suggesting that the significant pool (up to 14 micromoles per gram of nodule fresh weight) of this amide in cowpea nodules was not formed directly from fixation but may have accumulated as a consequence of phloem delivery.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1054455Documentos Relacionados
- Heterotrophic 15N2 Fixation and Distribution of Newly Fixed Nitrogen in a Rice-Flooded Soil System 1
- Factors Affecting the Acetylene to 15N2 Conversion Ratio in Root Nodules of Myrica gale L.
- Exploring Symbiotic Nitrogen Fixation and Assimilation in Pea Root Nodules by in Vivo 15N Nuclear Magnetic Resonance Spectroscopy and Liquid Chromatography-Mass Spectrometry1
- Dinitrogen Fixation by Cultures of Frankia sp CpIl Demonstrated by 15N2 Incorporation 1
- Azolla-Anabaena azollae Relationship: V. 15N2 Fixation, Acetylene Reduction, and H2 Production 12
