Microaerobic respiration and oxidative phosphorylation by soybean nodule mitochondria: implications for nitrogen fixation

The infected cells of soybean (Glycine max) root nodules require ATP production for ammonia assimilation and purine synthesis under microaerobic conditions. It is likely that the bulk of this demand is supplied through mitochondrial oxidative phosphorylation. Mitochondria purified from root nodules respired and synthesized ATP in sub-micromolar oxygen concentrations as measured by leghaemoglobin spectroscopy and luciferase luminescence. Both oxygen uptake and the apparent ATP/O ratio declined significantly as the oxygen concentration fell below 100 μmol m^?3. Cytochrome-pathway respiration by root nodule mitochondria had a higher apparent affinity for oxygen (Km 50 μmol m^?3) than did mitochondria isolated from roots (Km 125 μmol m^?3). Electron micrographs showed that mitochondria predominated at the periphery of infected cells adjacent to gas-filled intercellular spaces, where the oxygen concentration is predicted to be highest. Calculations of oxygen concentration and nitrogen fixation rates on an infected cell basis suggest that the measured rates of ATP production by isolated mitochondria are sufficient for the quantifiable in vivo requirements of ammonia assimilation and purine synthesis. The possible roles of mitochondrial respiration in the control of infected cell metabolism are also discussed.     

Differential expression of Iα- and IIα-globin genes in Norwegian dairy goats

Summary. Fast protein liquid chromatography (FPLC) and polyacrylamide gel electrophoresis were used to determine the ratio between ^Iα-and ^IIα-globin chains in Norwegian dairy goats. Three different phenotypes, designated normal (N) with ^Iα- to ^IIα-globin ratio 3:1, reversed (R) with ratio 1:2 and double-reversed (RR) with no ^Iα-globin, were described. Family studies indicated that the R animals were heterozygous, and the RR animal homozygous, for a haplotype without a functional ^Iα-globin product. Southern blot analysis of goat DNAs digested with six different restriction enzymes showed that the different ratios of α chain expression could not be due to a deletion of the ^Iα-gene and/or duplication or triplication of the ^IIα-globin genes. The homozygous reversed animal with no detectable ^Iα-globin had a mild anaemia.     

Restriction fragment length polymorphism of the caprine ß-globin gene cluster associated with the Hb ß-globin variants in Norwegian dairy goats

Restriction fragment length polymorphism (RFLP) analysis was used to characterize the beta-globin cluster in Norwegian dairy goats. In 122 individuals, different RFLP patterns were detected after BglII and PstI digestion and hybridization with a caprine beta-globin probe. The location of the polymorphic BglII and PstI sites were determined. The different RFLPs were in linkage disequilibrium with each other and with the beta-globin locus as studied at the protein level. A preferential association between certain RFLP haplotypes and beta-globin variants was observed. Polymorphic DNA fragments in the epsilon-globin genes were detected after MspI digestion and hybridization with a caprine epsilon-probe, and eight different band patterns were observed. Correlation between different MspI haplotypes and the beta-globin variants was determined.