Phenazine-1-carboxylic acid-producing Pseudomonas synxantha LBUM223 alters the transcriptome of Streptomyces scabies, the causal agent of potato common scab

Citation

Arseneault, T., Roquigny, R., Novinscak, A., Goyer, C., Filion, M. (2020). Phenazine-1-carboxylic acid-producing Pseudomonas synxantha LBUM223 alters the transcriptome of Streptomyces scabies, the causal agent of potato common scab. Physiological and Molecular Plant Pathology, [online] 110 http://dx.doi.org/10.1016/j.pmpp.2020.101480

Plain language summary

Common scab of potato is an important disease caused by the bacterial pathogen Streptomyces scabies. Biological control of this disease was previously demonstrated under controlled and field conditions using another bacteria, Pseudomonas synxantha LBUM223, through its production of an antibiotic (PCA). To better understand the effects of this antibiotic on the pathogen, new sequencing analyses of all genes expressed by the pathogen confronted with 1) the antibiotic-producing LBUM223, 2) a mutant of LBUM223 not able to produce the antibiotic, and 3) the purified antibiotic, were performed. The pathogen survived the exposure to all treatments. Following exposure to LBUM223 or the purified antibiotic (but not to the antibiotic-deficient mutant), the expression of 12%–14% of Streptomyces scabies’ genes were either over- or under-expressed compared to the pathogen alone, including key genes involved in capacity to cause disease, ability to persist in soil, and increased stress. This indicates that the antibiotic responsible for disease suppression induces changes in pathogen behavior but does not cause pathogen death, a mode of action which is seldom reported in scientific literature. This knowledge is important as the application of biocontrol agents is known to be highly variable depending on environmental conditions, and the understanding of the mechanisms involved in disease suppression can lead to increased success of disease control.

Abstract

Common scab of potato is an important disease caused by Streptomyces scabies. Biological control of this disease was previously demonstrated under controlled and field conditions using Pseudomonas synxantha LBUM223, a phenazine-1-carboxylic acid (PCA)-producer. To better understand the impact of PCA on the pathogen, RNA-seq analyses of S. scabies confronted with wild-type LBUM223, its isogenic PCA-deficient mutant and purified PCA were performed. Following exposure to wild-type LBUM223 or purified PCA (but not to the isogenic PCR-deficient mutant), 12%–14% of all S. scabies genes were differentially expressed, including key genes involved in pathogenicity/virulence, mycelium differentiation, and increased oxidative stress in S. scabies.