Structural and putative regulatory genes involved in cellulose synthesis in Rhizobium leguminosarum bv. trifolii

Six genes involved in cellulose synthesis in Rhizobium leguminosarum by. tr ifolii were identified using Tn5 mutagenesis. Four of them displayed homolo gy to the previously cloned and sequenced Agrobacterium tumefaciens cellula se genes celA, celB, celC and celE. These genes are organized similarly in R. leguminosarum by. trifolii. In addition, there were strong indications t hat two tandemly located genes, celR1 and celR2, probably organized as one operon, are involved in the regulation of cellulose synthesis. The deduced amino acid sequences of these genes displayed a high degree of similarity t o the Caulobacter crescentus DivK and PleD proteins that belong to the fami ly of two-component response regulators. This is to our knowledge the first report of genes involved in the regulation of cellulose synthesis. Results from attachment assays anal electron microscopic studies indicated that ce llulose synthesis in R. leguminosarum by. trifolii is induced upon close co ntact with plant roots during the attachment process.