Sucrose synthase in legume nodules is essential for nitrogen fixation

The role of sucrose synthase (SS) in the fixation of N was examined in the rug4 mutant of pea (Pisum sativum L.) plants in which SS activity was severely reduced. When dependent on nodules for their N supply, themutant plants were not viable and appeared to be incapable of effective N fixation, alth...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1999-07, Vol.120 (3), p.867-877
Main Authors: Gordon, A.J, Minchin, F.R, James, C.L, Komina, O
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Amino acids
Bacteroids
beta-fructofuranosidase
Biological and medical sciences
carbon
Economic plant physiology
enzyme activity
Enzymes
Fundamental and applied biological sciences. Psychology
isozymes
leghemoglobin
mortality
mutants
nitrogen
Nitrogen fixation
nitrogenase
nodulation
Nodules
nutrient availability
oxygen
Parasitism and symbiosis
Peas
Pisum sativum
Plant growth
Plant physiology and development
Plant-Microbe and Plant-Insect Interactions
Planting
Plants
root nodules
roots
shoots
Soybeans
Starches
substrates
sucrose synthase
Symbiosis
Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...)
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Summary:The role of sucrose synthase (SS) in the fixation of N was examined in the rug4 mutant of pea (Pisum sativum L.) plants in which SS activity was severely reduced. When dependent on nodules for their N supply, themutant plants were not viable and appeared to be incapable of effective N fixation, although nodule formation was essentially normal. In fact, N and C resources invested in nodules were much greater in mutant plants than in the wild-type (WT) plants. Low SS activity in nodules (present at only 10% of WT levels) resulted in lower amounts of total soluble protein and leghemoglobin and lower activities of several enzymes compared with WT nodules. Alkaline invertase activity was not increased to compensate for reduced SS activity. Leghemoglobin was present at less than 20% of WT values, so O(2) flux may have been compromised. The two components of nitrogenase were present at normal levels in mutant nodules. However, only a trace of nitrogenase activity was detected in intact plants and none was found in isolated bacteroids. The results are discussed in relation to the role of SS in the provision of C substrates for N fixation and in the development of functional nodules.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.120.3.867