Expression and Antagonistic Activity Against Plant Pathogens of the Phage Tail-like Protein from Burkholderia multivorans WS-FJ9.

Microorganisms exert antagonistic effects on pathogens through different mechanisms, thereby achieving biological control of plant diseases. Many Burkholderia strains can produce complex secondary metabolites and substances that have toxic effects on host cells. The phage tail-like bacteriocins (tailocins) is a compound with antibacterial activity. However, its function in B. multivorans has not yet been reported. This article explores the ability of B. multivorans WS-FJ9 to antagonise plant pathogenic fungi and oomycetes, screening the potential tailocins in the strain WS-FJ9 and verifying their function, to reveal its novel antimicrobial mechanisms. We found that WS-FJ9 had strong antagonistic effects on the plant pathogenic fungi Phomopsis macrospore and Sphaeropsis sapinea, and the pathogenic oomycete Phytophthora cinnamomi. The phage tail-like protein Bm_67459 was predicted from the WS-FJ9 strain genome. The Bm_67459 cDNA encoded 111 amino acid sequence, and the relative molecular weight was approximately 11.69 kDa, the theoretical isoelectric point (pI) was 5.49, and it was a hydrophilic protein. Bm_67459 had no transmembrane helix region or signal peptide, and it belonged to the Phage_TAC_7 super family. qRT-PCR results showed that Bm_67459 gene expression was significantly upregulated during contact between WS-FJ9 and P. cinnamomi. The purified Bm_67459 protein significantly inhibited P. cinnamomi mycelial growth at 10 μg·mL^-1. In summary, the WS-FJ9 strain had broad-spectrum anti-phytopathogenic activity, and the tailocin Bm_67459 was an important effector against the plant pathogen P. cinnamomi, which helps to reveal the antagonistic mechanism of this strain at the molecular level and provides excellent strain resources for the biological control of plant diseases.