The biological control bacterium Lysobacter enzymogenes
strain C3 can suppress fungal diseases by producing a suite of lytic enzymes and antimicrobial secondary metabolites. Previous studies have also shown that C3, when applied to grass and cereal plants, is capable of inducing systemic resistance against fungal pathogens. It is unknown, however, whether the bacterium has the ability to induce resistance in dicots and what signaling pathways are involved. In this study, the ability of C3 to trigger an induced resistance response in a dicot species was examined by applying the bacterium to leaves of soybean (Glycine max
‘Williams82’) and then measuring relative expression of salicylic acid (SA), jasmonic acid (JA), and ethylene pathway marker genes using qPCR. Allene oxide synthase (AOS) and aminocyclopropane-1-carboxylic acid synthase (ACS), upstream marker genes for jasmonate and ethylene pathways, respectively, were upregulated by C3 treatment, indicating activation of these pathways. A downstream marker gene for the SA pathway, PR-1, also was upregulated by C3, suggesting crosstalk between the pathways. The stage in the signaling pathways involved in the crosstalk is still unknown. Understanding the signaling events induced by C3 will provide a better understanding of the molecular mechanisms involved in disease suppression by the bacterium.
Key Words: Biocontrol, Induced Resistance, Lysobacter enzymogenes, defense signaling