Plants treated bi-weekly with 112-188 jag glufosinate to the root systems for three weeks had significantly greater specific nodulation. Nitrogenase activities were consistent with control plants. GC-MS analysis identified significant changes in leaf alanine, serine, glutamine and particularly asparagine. Transgenic Lotus plants positively screened for a transgene designed to constitutively suppress arginase activity consistently showed substantial accumulation of asparagine in the leaves. The results from this work show that N2 fixing activity can be significantly altered by modifying N metabolism by changing crucial enzyme activities such as GS. Further metabolic profiling associated with a complement of N metabolism mutants such as our asparagine accumulator will provide an excellent strategy for furthering our understanding of the specific aspects of N metabolism involved in N status regulation. There may also be potential for improving leguminous N2 fixing phenotypes, tailored for more efficient and sustainable agricultural systems.
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