The nitrate-reduction gene cluster components exert lineage-dependent contributions to optimization of Sinorhizobium symbiosis with soybeans.
Environ Microbiol
; 19(12): 4926-4938, 2017 Dec.
Article
in En
| MEDLINE
| ID: mdl-28967174
ABSTRACT
Receiving nodulation and nitrogen fixation genes does not guarantee rhizobia an effective symbiosis with legumes. Here, variations in gene content were determined for three Sinorhizobium species showing contrasting symbiotic efficiency on soybeans. A nitrate-reduction gene cluster absent in S. sojae was found to be essential for symbiotic adaptations of S. fredii and S. sp. III. In S. fredii, the deletion mutation of the nap (nitrate reductase), instead of nir (nitrite reductase) and nor (nitric oxide reductase), led to defects in nitrogen-fixation (Fix- ). By contrast, none of these core nitrate-reduction genes were required for the symbiosis of S. sp. III. However, within the same gene cluster, the deletion of hemN1 (encoding oxygen-independent coproporphyrinogen III oxidase) in both S. fredii and S. sp. III led to the formation of nitrogen-fixing (Fix+ ) but ineffective (Eff- ) nodules. These Fix+ /Eff- nodules were characterized by significantly lower enzyme activity of glutamine synthetase indicating rhizobial modulation of nitrogen-assimilation by plants. A distant homologue of HemN1 from S. sojae can complement this defect in S. fredii and S. sp. III, but exhibited a more pleotropic role in symbiosis establishment. These findings highlighted the lineage-dependent optimization of symbiotic functions in different rhizobial species associated with the same host.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Glycine max
/
Symbiosis
/
Sinorhizobium fredii
/
Nitrite Reductases
/
Nitrogen Fixation
Language:
En
Journal:
Environ Microbiol
Journal subject:
MICROBIOLOGIA
/
SAUDE AMBIENTAL
Year:
2017
Document type:
Article
Affiliation country:
China