Ferric Leghemoglobin in Plant-Attached Leguminous Nodules.

AUTOR(ES)

Lee, Kk.

RESUMO

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.

Documentos Relacionados

• Enzymatic and nonenzymatic mechanisms for ferric leghemoglobin reduction in legume root nodules.
• Cloning and sequence analysis of a cDNA encoding ferric leghemoglobin reductase from soybean nodules.
• Effects of Temperature on Infected Cell O2 Concentration and Adenylate Levels in Attached Soybean Nodules.
• Rheumatoid nodules.
• Bacterial heme synthesis is required for expression of the leghemoglobin holoprotein but not the apoprotein in soybean root nodules.