Genetic and functional analysis of novel Rhizobium tropici CIAT899 symbiosis-relevant loci identified through Tn5 insertion mutagenesis and selection of acid-sensitive mutants on acidified solid media

VINUESA PABLO F.; NEUMAN SILKOW B.; ARANDA RICKERT ADRIANA; STEELE HELEN; SPAINK H.P.; MÖRSCHEL E.; WERNER, D.

Ontario

Congreso; 13th International Congress on Nitrogen Fixation; 2001

MCB- Division of Molecular and Cellular Biosciences

Rhizobium tropici CIAT899 is highly acid tolerant and a good competitor for Phaseolus vulgaris nodule occupancy at low pH values. Using Tn5 mutagenesis, we identified an operon required for acid tolerance and nodulation competitiveness. The insertion was mapped to the 5' end of atvA, encoding a product with high sequence identity to the agrobacterial AcvB virulence protein. Complementation analyses indicated that atvA is an ortholog of acvB, both genes being required for acid tolerance, and that atvA is the second gene in an operon that is transcriptionally upregulated by acid shock.