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Two indirect methods for detecting ureide synthesis by nodulated legumes.
1Department of Plant Pathology, University of California, Riverside, California 92521.
Plant Physiology
|June 1, 1986
Summary
Two new methods detect altered ureide metabolism in legume nodules by measuring xanthine dehydrogenase activity. Allopurinol treatment causes chlorosis in ureide-producing legumes, while a pterin assay reveals fluorescence in nodules capable of ureide synthesis.
Area of Science:
- Plant Science
- Biochemistry
- Legume Biology
Background:
- Ureide metabolism is crucial for nitrogen fixation in many legumes.
- Xanthine dehydrogenase (EC 1.2.1.37) activity correlates with ureide production (allantoin and allantoic acid).
- Distinguishing between ureide and amide-producing legumes is important for understanding nitrogen assimilation.
Purpose of the Study:
- To develop and validate methods for detecting altered ureide metabolism in legume nodules.
- To differentiate between ureide- and amide-producing legume species.
- To assess ureide synthesis in wild soybean (Glycine soja).
Main Methods:
- Long-term allopurinol treatment of nodulated legumes and observation of leaf chlorosis.
- A rapid, qualitative assay using pterin and NAD+ to detect xanthine dehydrogenase activity via isoxanthopterin fluorescence.
- Examination of ureide abundance and xanthine dehydrogenase activity in wild soybean (Glycine soja).
Main Results:
- Allopurinol treatment induced severe chlorosis in leaves of N(2)-fed ureide-producing legumes (soybean, cowpea, lima bean), but not in amide-producers or ureide-producers fed nitrate/ammonium.
- The pterin-based assay detected isoxanthopterin fluorescence in nodules of ureide-producing legumes, indicating xanthine dehydrogenase activity, while amide-producers showed no fluorescence.
- Wild soybean (Glycine soja) exhibited high ureide abundance and xanthine dehydrogenase activity, confirming ureide production.
- Both methods successfully differentiated ureide-producing from amide-producing legumes and detected altered ureide metabolism.
Conclusions:
- Long-term allopurinol treatment is a reliable indicator for identifying ureide-producing legumes.
- The pterin-based fluorescence assay provides a rapid and sensitive method for estimating xanthine dehydrogenase activity and, consequently, ureide production.
- These methods are valuable tools for studying nitrogen fixation and metabolism in legumes, including wild soybean species.