Engineering D-glucose utilization in Azospirillum brasilense Sp7 promotes rice root colonization

Area of Science:

• Microbiology
• Plant-Microbe Interactions
• Genetic Engineering

Background:

• Azospirillum bacteria are known plant growth promoters.
• Azospirillum brasilense Sp7 has a broad host range but cannot efficiently use D-glucose.
• Azospirillum lipoferum 4B can utilize D-glucose.

Purpose of the Study:

• To identify genes in A. lipoferum 4B responsible for D-glucose utilization.
• To engineer A. brasilense Sp7 for enhanced D-glucose utilization.
• To assess the impact of engineered D-glucose utilization on rice root colonization.

Main Methods:

• Comparative genomics to identify candidate genes.
• Gene cloning into a broad host range expression vector.
• Mobilization of genes into A. brasilense Sp7 and growth assays.
• Construction of a transcriptional fusion of key metabolic genes.
• Evaluation of root colonization in rice seedlings.

Main Results:

• Identified genes in A. lipoferum 4B homologous to those involved in N-acetylglucosamine utilization in Pseudomonas aeruginosa PAO1.
• Engineered A. brasilense Sp7 with a gene cassette for D-glucose utilization.
• Demonstrated improved D-glucose utilization in engineered A. brasilense Sp7.
• Observed significantly enhanced root colonization of rice seedlings by the engineered strain.

Conclusions:

• The identified gene cassette confers D-glucose utilization ability to A. brasilense Sp7.
• Enhanced D-glucose utilization improves A. brasilense Sp7's ability to colonize rice roots.
• This genetic improvement holds potential for enhanced rice growth promotion.