Analysis of bacteria from the commensal root microbiome that suppress the plant host flg22 immune response

Abstract

A significant percentage of global loss in crop yields can be attributed to plant disease, indicating a need for more research and development in crop protection technologies that focus on disease detection and prevention. An abundance of scholarship has been con- ducted to explore how disease-causing pathogens modulate immunity in order to evade a plant’s immune response. However, plants are also a host to complex communities of commensal bacteria, some of which are beneficial to the plant. Commensal bacteria often express the same microbe-associated molecular patterns (MAMPs) as pathogens, which means they have the potential to trigger an immune response in their host. This study investigates the less-explored research question of how plants mount an effective immune response against pathogens while allowing the colonization of commensals. The aims of this study were to a) screen a bacteria collection for the presence of suppressors to the well-studied MAMP, flg22, and b) optimize the screening process through utilization of various assay techniques, particularly luminol-based (ROS) and peroxidase (POX) assays. We screened a 166-bacteria collection of Arabidopsis thaliana commensals for the ability to suppress the root-growth inhibition (RGI) phenotype caused by flg22. A suppressor and non-suppressor from this collection were then selected to undergo the POS and ROX assays. We identified 26 suppressors, including the positive control, and found interesting patterns in the phylum and order associated with most of the suppressors. While the ROS and POX assays did not provide meaningful results on the suppressive abilities of the bacteria, we were able to identify an optimal method for conducting these assays without the presence of bacteria. Our results will allow for further research into the mechanisms of suppression in our identified suppressors, which has important implications for crop protection technologies.