Decreased NADH glutamate synthase activity in nodules and flowers of alfalfa (Medicago sativa L.) transformed with an antisense glutamate synthase transgene
Open Access
- 1 January 2000
- journal article
- Published by Oxford University Press (OUP) in Journal of Experimental Botany
- Vol. 51 (342), 29-39
- https://doi.org/10.1093/jexbot/51.342.29
Abstract
Legumes obtain a substantial portion of their nitrogen (N) from symbiotic N2fixation in root nodules. The glutamine synthetase (GS, EC 6.3.1.2)/glutamate synthase (GOGAT) cycle is responsible for the initial N assimilation. This report describes the analysis of a transgenic alfalfa (Medicago sativaL.) line containing an antisense NADH‐GOGAT (EC 1.4.1.14) under the control of the nodule‐enhanced aspartate aminotransferase (AAT‐2) promoter. In one transgenic line, NADH‐GOGAT enzyme activity was reduced to approximately 50%, with a corresponding reduction in protein and mRNA. The transcript abundance for cytosolic GS, ferredoxin‐dependent GOGAT (EC 1.4.7.1), AAT‐2 (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) were unaffected, as were enzyme activities for AAT, PEPC and GS. Antisense NADH‐GOGAT plants grown under symbiotic conditions were moderately chlorotic and reduced in growth and N content, even though symbiotic N2 fixation was not significantly reduced. The addition of nitrate relieved the chlorosis and restored growth and N content. Surprisingly, the antisense NADH‐GOGAT plants were male sterile resulting from inviable pollen. A reduction in NADH‐GOGAT enzyme activity and transcript abundance in the antisense plants was measured during the early stages of flower development. Inheritance of the transgene was stable and resulted in progeny with a range of NADH‐GOGAT activity. These data indicate that NADH‐GOGAT plays a critical role in the assimilation of symbiotically fixed N and during pollen development.Keywords
This publication has 43 references indexed in Scilit:
- Nitrogenase Activity Is Affected by Reduced Partial Pressures of N2 and NO3- 1Plant Physiology, 1997
- Production and field performance of transgenic alfalfa (Medicago sativa L.) expressing alpha-amylase and manganese-dependent lignin peroxidaseEuphytica, 1995
- Genomic structure, expression and evolution of the alfalfa aspartate aminotransferase genesPlant Molecular Biology, 1994
- Molecular characterization of NADH-dependent glutamate synthase from alfalfa nodules.Plant Cell, 1993
- Preferential expression of an alpha-tubulin gene of Arabidopsis in pollen.Plant Cell, 1992
- Aspartate Aminotransferase in Alfalfa Root NodulesPlant Physiology, 1990
- Nitrogen Assimilating Enzyme Activities and Enzyme Protein during Development and Senescence of Effective and Plant Gene-Controlled Ineffective Alfalfa NodulesPlant Physiology, 1989
- Purification and Characterization of NADH-Glutamate Synthase from Alfalfa Root NodulesPlant Physiology, 1989
- Inhibition of Photosynthesis in Barley with Decreased Levels of Chloroplastic Glutamine Synthetase ActivityJournal of Experimental Botany, 1987
- A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye bindingAnalytical Biochemistry, 1976