Conservation of immunosuppression by Xanthomonadales commensals in Arabidopsis roots

点击翻译按钮获取中文摘要

Plant roots are colonized by a phylogenetically structured microbial community, called the root microbiota. We show that bacterial members of this community belonging to different taxa of the root microbiota differ in their ability to suppress immunity-associated responses in roots. The order Xanthomonadales defines a core lineage of the root microbiota of flowering plants, including Arabidopsis thaliana. Our preliminary results indicate that the ability of Xanthomonadales root commensals for immunosuppression is likely mediated by a conserved molecular mechanism. It remains unclear whether the commensals act only in specific root niches through a spatially and temporally controlled manipulation of defence responses. We selected the commensal Rhodanobacter R179, native to A. thaliana roots and representing the deepest branch of the order Xanthomonadales, and performed a mutant screen in planta using a library of R179 transposon insertion mutants. Ten defense suppression system (dss) R179 insertion mutants were identified that display impaired immunosuppressive activities compared with the wild-type commensal. We will investigate the presumed role of immunosuppression for spatio-temporal control of root colonization in mono-associations and community contexts. The dss mutants will also serve as basis to define the molecular mechanism(s) underlying Rhodanobacter R179 immunosuppression. We will examine the conservation of dss-dependent immunosuppression in phylogenetically diverse plantassociated Xanthomonadales commensals in roots. Finally, we will clarify the contribution of dss- and T3SS-dependent immunosuppression mechanisms and their potential mutual dependence for Xanthomonas pathogen colonisation in leaves.