FRD3 controls iron localization in Arabidopsis.

The frd3 mutant of Arabidopsis exhibits constitutive expression of its iron uptake responses and is chlorotic. These phenotypes are consistent with defects either in iron deficiency signaling or in iron translocation and localization. Here we present several experiments demonstrating that a functional FRD3 gene is necessary for correct iron localization in both the root and shoot of Arabidopsis plants.

Comparative analysis of the Bradyrhizobium japonicum sucA region.

To study the adjustments made to the tricarboxylic acid cycle during symbiosis of nitrogen-fixing rhizobia with their host legumes, we have characterized the genes encoding the alpha-ketoglutarate dehydrogenase enzyme complex in Bradyrhizobium japonicum. The genes were arranged in the order sucA-sucB-scdA-lpdA, where scdArepresents a short-chain dehydrogenase gene (GenBank accession No. AY049030).

Supply of O2 regulates demand for O2 and uptake of malate by N2-fixing bacteroids from soybean nodules.

Bacteroids, prepared anaerobically from soybean root nodules by fractional centrifugation or by sucrose or Percoll density-gradient methods, were retained within a stirred, flow-through reaction chamber and used to determine rates of respiration and N2 fixation at various rates of O2 supply. Liquid reaction solutions containing malate, oxyleghaemoglobin, dissolved N2 and various levels of dissolved O2 were passed through the reaction chamber at measured rates of flow. The relative oxygenation of leghaemoglobin in the chamber was determined automatically by spectrophotometry of the effluent solution, and the concentrations of free, dissolved O2 ([O2(free)]) and the rates of O2 consumption were calculated.