Mutants of Agrobacterium tumefaciens with elevated vir gene expression.

AUTOR(ES)

Pazour, G J

RESUMO

Expression of Agrobacterium tumefaciens virulence (vir) genes requires virA, virG, and a plant-derived inducing compound such as acetosyringone. To identify the critical functional domains of virA and virG, a mutational approach was used. Agrobacterium A136 harboring plasmid pGP159, which contains virA, virG, and a reporter virB:lacZ gene fusion, was mutagenized with UV light or nitrosoguanidine. Survivors that formed blue colonies on a plate containing 5-bromo-4-chloro-3-indolyl beta-D-galactoside were isolated and analyzed. Quantification of beta-galactosidase activity in liquid assays identified nine mutant strains. By plasmid reconstruction and other procedures, all mutations mapped to the virA locus. These mutations caused an 11- to 560-fold increase in the vegetative level of virB:lacZ reporter gene expression. DNA sequence analysis showed that the mutations are located in four regions of VirA: transmembrane domain one, the active site, a glycine-rich region with homology to ATP-binding sites, and a region at the C terminus that has homology to the N terminus of VirG.

Documentos Relacionados

• Mutation of the miaA gene of Agrobacterium tumefaciens results in reduced vir gene expression.
• A plant cell factor induces Agrobacterium tumefaciens vir gene expression
• Factor inducing Agrobacterium tumefaciens vir gene expression is present in monocotyledonous plants
• The regulatory VirA protein of Agrobacterium tumefaciens does not function at elevated temperatures.
• Characterization of three Agrobacterium tumefaciens avirulent mutants with chromosomal mutations that affect induction of vir genes.