The Agrobacterium fabrum efflux pump PecM is produced in response to the plant exudate 4-hydroxybenzaldehyde to avoid disruption of central metabolism

Document Type

Article

Publication Date

7-1-2025

Abstract

Agrobacterium fabrum is a phytopathogen that causes crown gall disease. In the rhizosphere, it encounters plant exudates, some of which are toxic, such as 4-hydroxybenzaldehyde (4HBA). Others, including 4-hydroxybenzoate (4HB), participate in the induction of virulence genes. A. fabrum encodes the transcription factor PecS, which has been reported to enhance bacterial fitness in the rhizosphere. The gene encoding PecS is divergent from pecM, which encodes an efflux pump. PecS represses both pecS and pecM, as evidenced by increased expression in the presence of the PecS ligand urate and by elevated pecM expression in a pecS disruption strain. We report here that the expression of pecM is induced selectively by 4HBA. Expression of genes encoding enzymes involved in the degradation of 4HB is induced by both 4HBA and 4HB, as expected; however, overexpression of pecM attenuates the induction by 4HBA, suggesting that 4HBA is a substrate for PecM. Consistent with this inference, untargeted metabolomics shows that 4HBA accumulates intracellularly when pecM is disrupted. Analysis of PecS by thermal stability assay and DNase I footprinting suggests that 4HBA is not a ligand for PecS. Taken together, our data suggest that 4HBA is a substrate for PecM.

Publication Source (Journal or Book title)

Journal of Bacteriology

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