In Planta Biocontrol of Pectobacterium atrosepticum by Rhodococcus erythropolis Involves Silencing of Pathogen Communication by the Rhodococcal Gamma-Lactone Catabolic Pathway

Abstract

The virulence of numerous Gram-negative bacteria is under the control of a quorum sensing process based on synthesis and perception of N-acyl homoserine lactones. Rhodococcus erythropolis, a Gram-positive bacterium, has recently been proposed as a biocontrol agent for plant protection against soft-rot bacteria, including Pectobacterium. Here, we show that the γ-lactone catabolic pathway of R. erythropolis disrupts Pectobacterium communication and prevents plant soft-rot. We report the first characterization and demonstration of N-acyl homoserine lactone quenching in planta. In particular, we describe the transcription of the R. erythropolis lactonase gene, encoding the key enzyme of this pathway, and the subsequent lactone breakdown. The role of this catabolic pathway in biocontrol activity was confirmed by deletion of the lactonase gene from R. erythropolis and also its heterologous expression in Escherichia coli. The γ-lactone catabolic pathway is induced by pathogen communication rather than by pathogen invasion. This is thus a novel and unusual biocontrol pathway, differing from those previously described as protecting plants from phytopathogens. These findings also suggest the existence of an additional pathway contributing to plant protection.

Transcriptome of the quorum-sensing signal-degrading Rhodococcus erythropolis responds differentially to virulent and avirulent Pectobacterium atrosepticum

“…Although the capacity of the NAHL-degrading R. erythropolis to obliterate QS-pathway, hence to markedly reduce the virulence gene expression in P. atrosepticum is well documented (Cirou et al, 2007;Barbey et al, 2013), how P. atrosepticum could modify the R. erythropolis transcriptome is not known. In this work, we reported the structural and functional genomics of the NAHL-degrading R. erythropolis strain R138.…”

Conversion of the Pseudomonas aeruginosa Quinolone Signal and Related Alkylhydroxyquinolines by Rhodococcus sp. Strain BG43

“…and P. aeruginosa coexisted in this sample. The identification of the qsdA gene in strain BG43, which codes for an AHL lactonase active against a broad range of AHL signal molecules (21,46,51), suggests that strain BG43 can also disrupt AHL-based communication, like other Rhodococcus strains that contain qsdA (21,23).…”

“…Interestingly, a number of Rhodococcus isolates can utilize AHL signal molecules as carbon sources. In Rhodococcus erythropolis W2, R. erythropolis R138, and related strains, the ability to efficiently degrade AHLs appears to be correlated with a conserved ␥-lactone degradation pathway, with the lactonase QsdA as the key enzyme (21)(22)(23). R. erythropolis strains possessing this pathway significantly reduced tissue maceration of potato tubers by the soft-rot pathogens Pectobacterium carotovorum subsp.…”

“…R. erythropolis strains possessing this pathway significantly reduced tissue maceration of potato tubers by the soft-rot pathogens Pectobacterium carotovorum subsp. carotovorum and Pectobacterium atrosepticum (23)(24)(25).…”

Root exudate ofSolanum tuberosumis enriched in galactose-containing molecules and impacts the growth ofPectobacterium atrosepticum

“…Pectobacterium atrosepticum was grown in polygalacturonic acid (PGA) minimal medium supplemented with 0Á4 % (w/v) polygalacturonic acid (Sigma-Aldrich, St Louis, MO) at 25 C as previously described (Smadja et al, 2004a, b;Barbey et al, 2013). Infection assays were performed by deposition of 50 mL of a bacterial solution (15Á10 7 Colony Forming Unit (CFU) mL À1 ) onto the root apex of S. tuberosum.…”