Biological nitrogen fixation in maize: optimizing nitrogenase expression in a root-associated diazotroph

Area of Science:

• Microbiology
• Plant Science
• Agricultural Science

Background:

• Plants rely on root-associated microbes for growth and nutrient acquisition.
• Free-living diazotrophic bacteria provide essential nitrogen, a role often overlooked in agriculture.
• High nitrogen fertilization can reduce symbiotic nitrogen fixation efficiency in plants.

Purpose of the Study:

• To reprogram a novel root-associated diazotroph for sustained nitrogen fixation.
• To optimize nitrogen fixation in corn using gene-edited Kosakonia sacchari.
• To enhance ammonium production in the presence of exogenous nitrogen inputs.

Main Methods:

• Isolation and characterization of Kosakonia sacchari from corn roots.
• Analysis of the nitrogen regulatory network in Kosakonia sacchari.
• Gene editing of key regulatory nodes to enhance nitrogen fixation.

Main Results:

• Wild-type Kosakonia sacchari showed repressed nitrogen fixation with available nitrogen.
• Engineered strains maintained high nitrogen fixation levels in corn rhizospheres.
• This occurred even under conditions with exogenous nitrogen supply in greenhouse and field trials.

Conclusions:

• Reprogramming nitrogen fixation pathways in Kosakonia sacchari restores function despite nitrogen fertilization.
• Genetically modified strains offer a promising avenue for supplying fixed nitrogen to cereal crops.
• This approach could lead to more efficient and sustainable agricultural practices.