Photorespiratory Metabolism and Nodule Function: Behavior of Lotus japonicus Mutants Deficient in Plastid Glutamine Synthetase
Two photorespiratory mutants of Lotus japonicus deficient in plastid glutamine synthetase (GS2) were examined for their capacity to establish symbiotic association with Mesorhizobium loti bacteria. Biosynthetic glutamine synthetase (GS) activity was reduced by around 40% in crude nodule extracts fro...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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The American Phytopathological Society
2012-02-01
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| Series: | Molecular Plant-Microbe Interactions |
| Online Access: | https://apsjournals.apsnet.org/doi/10.1094/MPMI-07-11-0200 |
| Summary: | Two photorespiratory mutants of Lotus japonicus deficient in plastid glutamine synthetase (GS2) were examined for their capacity to establish symbiotic association with Mesorhizobium loti bacteria. Biosynthetic glutamine synthetase (GS) activity was reduced by around 40% in crude nodule extracts from mutant plants as compared with the wild type (WT). Western blot analysis further confirmed the lack of GS2 polypeptide in mutant nodules. The decrease in GS activity affected the nodular carbon metabolism under high CO2 (suppressed photorespiration) conditions, although mutant plants were able to form nodules and fix atmospheric nitrogen. However, when WT and mutant plants were transferred to an ordinary air atmosphere (photorespiratory active conditions) the nodulation process and nitrogen fixation were substantially affected, particularly in mutant plants. The number and fresh weight of mutant nodules as well as acetylene reduction activity showed a strong inhibition compared with WT plants. Optical microscopy studies from mutant plant nodules revealed the anticipated senescence phenotype linked to an important reduction in starch and sucrose levels. These results show that, in Lotus japonicus, photorespiration and, particularly, GS2 deficiency result in profound limitations in carbon metabolism that affect the nodulation process and nitrogen fixation. |
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| ISSN: | 0894-0282 1943-7706 |