Cell wall-mediated root development is targeted by a soil-borne bacterial pathogen to promote infection.

Plant pathogens manipulate host development, facilitating colonization and proliferation. Ralstonia solanacearum is a soil-borne bacterial pathogen that penetrates roots and colonizes plants through the vascular system, causing wilting and death. Here, we find that RipAC, an effector protein from R. solanacearum , alters root development in Arabidopsis , promoting the formation of lateral roots and root hairs. RipAC interacts with CELLULOSE SYNTHASE (CESA)-INTERACTIVE PROTEIN 1 (CSI1), which regulates the activity of CESA complexes at the plasma membrane. RipAC disrupts CESA-CSI1 interaction, leading to a reduction in cellulose content, root developmental alterations, and a promotion of bacterial pathogenicity. We find that CSI1 also associates with the receptor kinase FERONIA, forming a complex that negatively regulates immunity in roots; this interaction, however, is not affected by RipAC. Our work reveals a bacterial virulence strategy that selectively affects the activities of a host target, promoting anatomical alterations that facilitate infection without causing activation of immunity. [Display omitted] • RipAC, a Ralstonia effector protein, associates with CSI1 and disrupts cellulose biosynthesis • This RipAC activity promotes the formation of lateral roots during Ralstonia infection • Lateral root emergence contributes to Ralstonia invasion and colonization of the host plant • CSI1 differentially regulates plant immune responses in shoots and roots Yu et al. show that Ralstonia , a soil-borne bacterial pathogen, secretes an effector protein inside plant cells to disrupt cellulose biosynthesis and promote the formation of lateral roots, providing additional entry points for invasion of host plants. This shows that Ralstonia manipulates root development in order to promote infection. [ABSTRACT FROM AUTHOR]