Rhizosphere microbes mitigate the shade avoidance responses in Arabidopsis

Shade avoidance responses are defined as the plastic responses of plants to neighboring shading signals through changes in the light spectrum, which limit planting density in modern agricultural practices. Here, we found that shade avoidance responses depend on soil microbes and identified a microbe-root-shoot circuit that bolsters aboveground shade tolerance in Arabidopsis thaliana. Rhizosphere microbes systemically regulate the expression of aboveground shade-responsive genes, which are associated with the altered homeostasis of jasmonic-acid- and salicylic-acid-related metabolites. We further found that the plasma-membrane-localized pattern recognition receptors FLS2/BAK1 and transcription factors MYC2/phytochrome-interacting factors (PIFs)/LONG HYPOCOTYL5 (HY5) are required for rhizosphere-microbe-alleviated shade avoidance. Our study characterized a signaling cascade (FLS2/BAK1-MYC2-PIF4/HY5) and provided a strategy for mitigating aboveground shade responses using rhizosphere microorganisms.