The chromosomal virulence gene, chvE, of Agrobacterium tumefaciens is regulated by a LysR family member

Abstract

Certain plant phenolic compounds and monosaccharides induce the transcription of virulence (vir) genes of Agrobacterium tumefaciens through the VirA-VirG two-component regulatory system. The product of the chromosomal virulence gene chvE is homologous to galactose-binding protein of Escherichia coli and is required for vir gene induction by sugars. Adjacent to, but divergent in transcription from, chvE is an open reading frame, now termed gbpR (galactose-binding protein regulator), that is homologous to the LysR family of transcriptional regulators. chvE::lacZ expression was induced by L-arabinose, D-galactose, and D-fucose when gbpR was present. In the absence of inducer, GbpR repressed chvE::lacZ expression. In addition, GbpR negatively regulated its own expression.