2023 AIChE Annual Meeting
Use of a Subtilase By Commensal Microbiota to Suppress the flg22-Induced Immune Response in Arabidopsis thaliana
Plants have an innate immune system that is triggered in response to microbe-associated molecular patterns (MAMPs). Flg22 is a MAMP that varies by species and is found in the FliC subunit of bacterial flagella. An immune eliciting epitope of flg22 is present in the FliC protein of Dyella japonica MF079, an Arabidopsis thaliana Columbia-0 (Col-0) root commensal. Yet, the presence of this bacterium does not trigger the A. thaliana Col-0 immune system. Furthermore, both live bacteria and cell-free culture supernatant from Dja MF079 can suppress the plant immune system in response to free canonical flg22. Dyella Immunosuppressive Subtilase 1 (Dis1) was identified as an actor in this immune suppression using knockout genetics. Both bacterial and supernatant GUS assays have shown that Dis1 is important in plant immune suppression but not the only cause of immunosuppression by Dja MF079. Furthermore, by incubating flg22 in Dja MF079 wild type and ÎDis1 supernatant we show Dis1 alters flg22 such that it is not perceived by the plant. Additionally, homology was utilized to identify and knockout Dis1 homologs in other root commensal bacteria. These homologs, Ralstonia Immunosuppressive Subtilase 1/2 and Luteibacter Immunosuppressive Subtilase 1, were also found to contribute to immune suppression in strains from the respective genera. These data suggest Dis1 and homologous subtiliases in plant microbiota are an important mechanism by which commensals suppress activation of the flg22 immune response in plants.