Journal
PLANT CELL AND ENVIRONMENT
Volume 33, Issue 12, Pages 2162-2172Publisher
WILEY
DOI: 10.1111/j.1365-3040.2010.02214.x
Keywords
nitrogen fixation; nodule; symbiosis
Categories
Funding
- German Science Foundation (DFG) [SCHU 1602/3-1]
Ask authors/readers for more resources
Nitrogen fixation in legumes is downregulated through a whole plant N feedback mechanism, for example, when under stress. This mechanism is probably triggered by the impact of shoot-borne, phloem-delivered compounds. However, little is known about any whole-plant mechanism that might upregulate nitrogen fixation, for example, under N deficiency. We induced emerging N-deficiency through partial excision of nodules from Medicago truncatula plants. Subsequently, the activity and composition of the remaining nodules and shifts in concentration of free amides/amino acids in the phloem were monitored. Furthermore, we mimicked these shifts through artificial feeding of gamma-aminobutyric acid (GABA) into the phloem of undisturbed plants. As a result of increased specific activity of nodules, N-2 fixation per plant recovered almost completely 4-5 d after excision. The concentration of amino acids, sugars and organic acids increased strongly in the upregulated nodules. A concomitant analysis of the phloem revealed a significant increase in GABA concentration. Comparable with the effect of nodule excision, artificial GABA feeding into the phloem resulted in an increased activity and higher concentration of amino acids and organic acids in nodules. It is concluded that GABA might be involved in upregulating nodule activity, possibly because of its constituting part of a putative amino acid cycle between bacteroids and the cytosol.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available