The small-molecule pifithrin-α deactivates ETR1 to repress shade avoidance in .

Shade avoidance syndrome (SAS) commonly occurs in plants sensing shading and the proximity of neighbors, leading to morphological and physiological changes that are detrimental to plant health and consequently crop yield. Controlling SAS could be beneficial for sustainable agriculture. Here, we performed a phenotype-based chemical screening in and identified pifithrin-α (PFT-α) as a compound that suppresses shade-induced hypocotyl elongation and gene expression. Through genetic, biochemical, and molecular approaches, we demonstrated that PFT-α mimics ethylene by deactivating the ethylene receptor 1 (ETR1). Accumulated ethylene-insensitive 3 (EIN3) influences the expression of ( and ) and subsequently inhibits shade-induced hypocotyl elongation. Our findings not only provide molecular insights into SAS but also suggest that PFT-α, acting as a potent ethylene mimic, plays a crucial role in hormone-regulated plant development and holds potential for modulating SAS in agricultural practices.