Analysis of hydroxycinnamic acids degradation in Agrobacterium fabrum reveals a CoA-dependent, beta-oxidative deacetylation pathway
Résumé
The soil and rhizosphere inhabiting bacterium Agrobacterium fabrum (genomospecies G8 of the A. tumefaciens species complex) is known to have species-specific genes involved in ferulic acid degradation. Here, we characterized by genetic and analytical means intermediates of degradation as feruloyl-CoA, 4-hydroxy-3-methoxyphenyl-β-hydroxypropionyl-CoA, 4-hydroxy-3-methoxyphenyl-β-ketopropionyl-CoA, vanillic acid and protocatechuic acid. Genes atu1416, atu1417 and atu1420 have been experimentally shown necessary for the degradation of ferulic acid. Moreover, genes atu1415 and atu1421 have been experimentally demonstrated to be essential for this degradation and are proposed to encode a phenylhydroxypropionyl-CoA dehydrogenase and a HMPKP-CoA β-keto-thiolase, respectively. We thus demonstrated that the A. fabrum-hydroxycinnamic degradation pathway is an original coenzyme-A-dependent β-oxidative deacetylation that could also transform p-coumaric and caffeic acids. Finally, we showed that this pathway enables metabolism of toxic compounds from plants and their use for growth, likely providing this species an ecological advantage in hydroxycinnamic-rich environments such as plant roots or decaying plant materials.