Carbon Metabolism in the Rhizobium- Legume Symbiosis

Nitric oxide synthase activity is required for development of functional nodules in soybean

“…NCR peptides appear to be specific for legumes belonging to the IRLC in their action because they occur only in this clade, but ectopic expression of NCR peptides in non-IRLC legumes such as Lotus japonicus and Glycine max confer the terminal differentiation phenotype to the non-IRLC legumes (Van de Velde et al, 2010). The bacteroids in the nodules fix atmospheric nitrogen into ammonia that can be used by plants as a source of biologically usable nitrogen, while the rhizobia benefit from nutrients derived from the plant to support their metabolic activities (Khan et al, 1995). The nitrogen derived from this symbiotic relationship can be sufficient to sustain legume growth in nitrogen-deprived soils and can thus be environmentally relevant, as it can enrich the soil with nitrogen without the use of synthetic fertilizer (Vance, 2002).…”

Identification of new up-regulated genes under drought stress in soybean nodules

“…In the nodule, rhizobia are differentiated into bacteroids that can reduce atmospheric nitrogen (N 2 ) into ammonia. In exchange, plants provide photosynthetic nutrients to the bacteria, essential for maintenance of high N 2 fixation activity (Khan et al, 1995). This biological process represents a fundamental source of ammonia for the normal growth and development of soybean.…”

The Bradyrhizobium japonicum aconitase gene (acnA) is important for free-living growth but not for an effective root nodule symbiosis

“…Indeed, the function of citrate as a siderophore in B. japonicum has been shown (17,18). ␣-Ketoglutarate is required for the formation of glutamate; however, whether bacteroid glutamate arises from ammonia assimilation in the bacteroid or by the plant is still an open question (23,28,45,46).…”

“…Rhizobium meliloti mutants lacking succinate dehydrogenase (15), ␣-ketoglutarate dehydrogenase (10), or isocitrate dehydrogenase (29) are unable to fix nitrogen in symbiosis (Fix Ϫ ). The genes sucA and sucB, encoding components of ␣-ketoglutarate dehydrogenase (23), and icd, encoding isocitrate dehydrogenase (29), have been cloned. Also, the isolation of R. meliloti gltA, which codes for citrate synthase, has been reported (23).…”

“…The genes sucA and sucB, encoding components of ␣-ketoglutarate dehydrogenase (23), and icd, encoding isocitrate dehydrogenase (29), have been cloned. Also, the isolation of R. meliloti gltA, which codes for citrate synthase, has been reported (23). Rhizobium tropici possesses two approximately 90% identical genes encoding citrate synthase, pcsA and ccsA, representing plasmid-borne and chromosomal copies, respectively (21,32).…”