In Vivo31P NMR Spectroscopic Studies of Soybean Bradyrhizobium Symbiosis

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Abstract
31P NMR spectroscopy was used to study in vivo the symbiotic state established between soybean (Glycine max [L.] Merr. cv Williams) and Bradyrhizobium japonicum (USDA 110 and 138). Different experimental conditions were used to maintain perfused, respiring detached or attached nodules in an NMR magnet. The pH of the perfusion medium affected the cytoplasmic pH and the resolution of the spectra. The internal Pi content and distribution were assessed as a function of nodule age and greenhouse growth conditions and the rate of glucose and 2-deoxyglucose uptake into nodules in split and intact states. The major metabolites (glucose-6-P, fructose-1,6-diP, P-choline, Pi, NTP, UDP-glc, and NAD) were readily identified from 31P NMR spectra of perchloric acid extracts of nodules with the exception of one unknown phosphorus metabolite. Nodules stressed by glucose depreivation demonstrated movement of Pi between the vacuole and cytoplasmic compartments not previously observed in 31P NMR studies.