ELUCIDATING THE MECHANISM OF PLANT IMMUNE SUPPRESSION BY DYELLA JAPONICA USING BACTERIAL GENETIC ENGINEERING

Abstract

The plant root immune system is a central aspect of plant immunity, as it essential for modulating interactions between plants and the soil microbiome. In these plant-microbiome interactions, the plant immune system defends plants by recognizing signature motifs presented by bacteria, and consequently activates defense signaling pathways in response to these motifs to prevent disease. However, the activation of defense pathways comes at a significant cost to plant growth, as limited energy resources are diverted from cell growth for the production of defense compounds. However, the plant root immune system is not activated in response to all bacteria, and many commensal species are able to avoid immune detection through unknown mechanisms. Therefore, the aims of this study are to investigate one potential mechanism of commensal bacteria immune evasion through the secretion of a serine protease. Herein, the activity of this serine protease is assayed in protein expression, gain-of-function, and loss-of-function experiments that measure the plant root immune response. By using genetic engineering techniques, the gene for the serine protease is either knocked-in or knocked-out of bacteria that are introduced to Arabidopsis seedlings, and the activation of defense pathways are observed. In all, this study contributes towards the development of bacterial-based plant probiotics that optimize plant-microbiome interactions and modulate plant immunity to enhance plant growth. In turn, these findings can be applied to agricultural and biofuel technologies, both with substantial implications for human health.