ABSTRACT
The genus Streptomyces has been unceasingly highlighted for the versatility and diversity of the antimicrobial agents they produce. Moreover, it is a heavily sequenced taxon in the phylum Actinobacteria. In this study, 47 sequence profiles were identified as proteins highly conserved within the genus Streptomyces. Significant hits to the 38 profiles were found in more than 2000 Streptomyces genomes, 11 of which were further conserved in more than 90% of Actinobacterial genomes analyzed. Only a few genes corresponding to these sequence profiles were functionally characterized, which play regulatory roles in the morphology and biosynthesis of antibiotics. Here a highly conserved sequence, namely, SHC-AMP (Streptomyces highly conserved antimicrobial peptide), which exhibited antimicrobial activity against bacterial and fungal plant pathogens, was reported. In particular, Arabidopsis thaliana was effectively protected against infection with Pseudomonas syringae pv. tomato DC3000 by treatment with this peptide. Results indicated the potential application of this peptide as an antimicrobial agent for control of plant diseases. Our results suggest putative target genes for controlling Streptomyces spp., including the one exhibiting antimicrobial activity against a wide range of phytopathogens.
ABSTRACT
Pectobacterium atrosepticum (P. atrosepticum: Pba) which causes potato soft rot and blackleg is a notorious plant pathogen worldwide. Discovery of new types of antimicrobial chemicals that target specifically to virulence factors such as bacterial motility and extracellular enzymes is required for protecting crops from pathogenic infection. A transcriptomic analysis of Pba upon hopeaphenol treatment revealed that bacterial motility-related gene expression, including a master regulator flhDC genes, was significantly influenced by hopeaphenol. We further generated a double knock-out mutant of flhDC genes by CRISPR/Cas9 system and confirmed phenotypic changes in bacterial motility, transcription of extracellular enzymes, and disease development consistent with the result of wild-type treated with hopeaphenol. The hopeaphenol-treated Pba strains, wild-type, double mutant, and complemented strain were unable to secrete the enzymes in vitro, while ΔflhDC double mutant strain reduced the secretion. Thus, our study supports that FlhDC is essential for the virulence of Pba, and proposes that hopeaphenol modulates FlhDC-dependent virulence pathways, suggesting a potential of hopeaphenol as an anti-virulence agent to manage potato soft rot and blackleg diseases.
ABSTRACT
Antibiotic resistance has become increasingly prevalent in the environment. Many alternative strategies have been proposed for the treatment and prevention of diverse diseases in agriculture. Among them, the modulation of bacterial virulence to bypass antibiotic resistance or boost plant innate immunity can be considered a promising drug target. Plant-produced natural products offer a broad spectrum of stereochemistry and a wide range of pharmacophores, providing a great diversity of biological activities. Here, we present a perspective on the putative role of plant-produced resveratrol oligomers as anti-virulence and plant-immune priming agents for efficient disease management. Resveratrol oligomers can decrease (1) bacterial motility directly and (2) indirectly by attenuating the bacterial type III secretion system (TT3S). They induce enhanced local immune responses mediated by two-layered plant innate immunity, demonstrating (3) a putative plant immune priming role.