Date of this Version
Walnut, Jessica. 2019. Hormonal signaling induced in soybean by Lysobacter enzymogenes strain C3. Masters Thesis. University of Nebraska-Lincoln, Lincoln, NE.
The biological control bacterium Lysobacter enzymogenes strain C3 has been shown to suppress fungal diseases by producing a suite of lytic enzymes and antimicrobial secondary metabolites. Previous studies have found that C3, when applied to grass and cereal plants, also is capable of inducing local and 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. This study assessed the ability of C3 to trigger local and systemic induced resistance responses in soybean (Glycine max ‘Williams82’) by analyzing relative expression of salicylic acid (SA), jasmonic acid (JA), and ethylene pathway genes using qPCR. The first set of experiments determined that foliar treatments with C3 induced all three defense hormone pathways in the treated leaves. Upstream marker genes Allene Oxide Synthase (AOS) and Aminocyclopropane-1-carboxylic acid Synthase (ACS) for jasmonate and ethylene pathways respectively, were upregulated by C3 treatment, indicating activation of these pathways. Downstream marker genes Pathogenesis Related Proteins 1 (PR1) and Pathogenesis Related Proteins 3 (PR3) for the SA and JA/ET pathways, respectively, were also upregulated by C3 treatment. The second set of experiments involved C3 treatment applications to soybean roots and measuring changes in transcription of PR genes in the foliage. Systemic induction of PR1 and PR3 was not observed after root treatment. This is the first study to provide evidence of a biocontrol bacteria inducing three hormone pathways upon application to soybean foliage. The ability of C3 to induce systemic resistance in dicots after root treatment remains unclear.
Advisor: Gary Yuen