Interference with host root growth and immunity by root microbiota members and its genetic determinants

Abstract

Plant-associated microbes can engage not only in symbiotic or pathogenic interactions with their host but also in root colonization without causing a clearly beneficial or harmful effect on host growth. Yet, it remains largely unknown how these microbes influence host physiology and how plants regulate such interactions. We have already found that commensal bacteria associated with Arabidopsis thaliana roots interfere with host root growth and immunity (Garrido-Oter et al., 2018). Specifically, the growth inhibition triggered by chronic immune activation, which is thought to be a consequence of the plant growth-defense tradeoff (Nakano and Shimasaki, 2024), is significantly suppressed by a subset of these commensal bacteria, implying a crucial role for root immunity in regulating plant-commensal interactions. Our forward genetic screening for mutants that do not suppress host immune responses identified six candidate genes required for this suppressive activity. These include genes involved in DNA methylation and protein phosphorylation, pointing to a bacterial signaling cascade that manipulates host immune responses. Interestingly, we revealed that the host immune status does not necessarily dictate the colonizing capacity of root-associated commensal bacteria. Taken together with recent studies (e.g. Tzipilevich et al., 2021; Wippel et al., 2021; Ordon et al., 2025), our results suggest that root immunity regulates root-commensal interactions in fundamentally different ways from how leaf immunity controls leaf-pathogen interactions.

Reference

Garrido-Oter*, Nakano*, Dombrowski*, et al., Cell Host & Microbe, 2018. https://doi.org/10.1016/j.chom.2018.06.006(link is external)

Nakano and Shimasaki, Plant and Cell Physiology, 2024. https://doi.org/10.1093/pcp/pcae033(link is external)

Basak et al., New Phytologist, 2024. https://doi.org/10.1111/nph.19289(link is external)