Abstract
Leghemoglobin (Lb) is essential for nitrogen fixation by intact leguminous nodules. To determine whether ferric Lb (Lb3+) was detectable in nodules under normal or stressed conditions, we monitored the status of Lb in intact nodules attached to sweet clover (Melilotus officinalis) and soybean (Glycine max [L.] Merr.) roots exposed to various conditions. The effects of N2 and O2 streams and elevated nicotinate levels on root-attached nodules were tested to determine whether the spectrophotometric technique was showing the predicted responses of Lb. The soybean and sweet clover nodules' Lb spectra indicated predominantly ferrous Lb and LbO2 in young (34 d) plants. As the nodule aged beyond 45 d, it was possible to induce Lb3+ with a 100% O2 stream (15 min). At 65 d without inducement, the nodule Lb status indicated the presence of some Lb3+ along with ferrous Lb and oxyferrous Lb. Nicotinate and fluoride were used as ligands to identify Lb3+. Computer-calculated difference spectra were used to demonstrate the changes in Lb spectra under different conditions. Some conditions that increased absorbance in the 626 nm region (indicating Lb3+ accumulation) were root-fed ascorbate and dehydroascorbate, plant exposure to darkness, and nodule water immersion.
Full Text
The Full Text of this article is available as a PDF (614.4 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Appleby C. A. Properties of leghaemoglobin in vivo, and its isolation as ferrous oxyleghaemoglobin. Biochim Biophys Acta. 1969;188(2):222–229. doi: 10.1016/0005-2795(69)90069-5. [DOI] [PubMed] [Google Scholar]
- Appleby C. A., Wittenberg B. A., Wittenberg J. B. Nicotinic Acid as a ligand affecting leghemoglobin structure and oxygen reactivity. Proc Natl Acad Sci U S A. 1973 Feb;70(2):564–568. doi: 10.1073/pnas.70.2.564. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Evans H. J., Koch B., Klucas R. Preparation of nitrogenase from nodules and separation into components. Methods Enzymol. 1972;24:470–476. doi: 10.1016/0076-6879(72)24092-7. [DOI] [PubMed] [Google Scholar]
- Ji L., Becana M., Klucas R. V. Involvement of Molecular Oxygen in the Enzyme-Catalyzed NADH Oxidation and Ferric Leghemoglobin Reduction. Plant Physiol. 1992 Sep;100(1):33–39. doi: 10.1104/pp.100.1.33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ji L., Becana M., Sarath G., Klucas R. V. Cloning and sequence analysis of a cDNA encoding ferric leghemoglobin reductase from soybean nodules. Plant Physiol. 1994 Feb;104(2):453–459. doi: 10.1104/pp.104.2.453. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ji L., Becana M., Sarath G., Shearman L., Klucas R. V. Overproduction in Escherichia coli and Characterization of a Soybean Ferric Leghemoglobin Reductase. Plant Physiol. 1994 Sep;106(1):203–209. doi: 10.1104/pp.106.1.203. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ji L., Wood S., Becana M., Klucas R. V. Purification and characterization of soybean root nodule ferric leghemoglobin reductase. Plant Physiol. 1991 May;96(1):32–37. doi: 10.1104/pp.96.1.32. [DOI] [PMC free article] [PubMed] [Google Scholar]