Cloning and analysis of Agrobacterium tumefaciens C58 loci involved in glutamine biosynthesis: Neither the glnA (GSI) nor the glnII (GSII) gene plays a special role in virulence

Summary Using heterologous complementation of a glutamine synthetase deficient (glnA; GS^-) Escherichia coli mutant strain and heterologous DNA hybridization probes from Rhizobium meliloti and Bradyrhizobium japonicum, three distinct Agrobacterium tumefaciens loci involved in glutamine biosynthesis were identified. These loci correspond to the glnA (GSI), glnII (GSII) and a third previously unidentified locus, which is capable of complementing an E. coli glnA mutant, but may be cryptic in A. tumefaciens. The gene products encoded by the cloned glnA and glnII loci were identified using maxicells. Single insertion mutations in the glnA (GSI) and glnII (GSII) genes and a glnA glnII double mutant were constructed using gene replacement techniques. These mutant strains were examined for GSI and II activities, for growth on a variety of nitrogen (N) sources and for virulence properties on Kalanchoë plants. Neither glnA (GSI) nor glnII (GSII) were found to be essential for tumour induction on Kalanchoë nor for opine catabolism.