Molecular characterization of Tn5-induced symbiotic (Fix-) mutants of Rhizobium meliloti.

摘要: Abstract To investigate the expression of specific symbiotic genes during development nitrogen-fixing root nodules, we conducted a systematic analysis nodule-specific proteins and RNAs produced after inoculation alfalfa roots with series Rhizobium meliloti mutants generated by site-directed transposon Tn5 mutagenesis. The mutagenized region genome covered approximately 10 kilobases included encoding nitrogenase polypeptides. All mutant strains that were analyzed but several nodules failed to fix nitrogen (Nod+ Fix- phenotype). accumulated reduced levels host plant protein leghemoglobin. In addition, insertions in operon (nifHDK genes) eliminated some or all polypeptides nifHDK RNA transcripts, depending on site insertion. Finally, mutation 5 upstream from resulted absence three their corresponding RNAs, suggesting this may serve regulatory function fixation. studies presented here indicate mutagenesis coupled biochemical nodule allows identification products gene regions as well assignment functions previously unidentified R. genome.