Use of Green Fluorescent Protein to Detect Expression of nif Genes of Azoarcus sp. BH72, a Grass-Associated Diazotroph, on Rice Roots

A gfp (green fluorescent protein) cassette for transcriptional fusions has been developed to study gene expression in Azoarcus sp. BH72 in association with plant roots. The bacteria expressed nitrogenase genes (nifHDK) in the rhi-zosphere, on root tips, and in epidermal cells of rice seedlings. Green fluorescent protein fusions also visualized promoter activity of single cells in soil.