The small molecule Pifithrin–α deactivates ETR1 to repress shade avoidance in Arabidopsis

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 prove beneficial for sustainable agriculture.Here, we performed a phenotype-based chemical screen in Arabidopsis and identified pfifithrin (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 ETR1. This action influences the expression of Phytochrome-Interacting Factors (PIF4 and PIF7) and subsequently inhibits shade-induced hypocotyl elongation. Our findings suggest that PFT-α, acting as a potent ethylene mimic, plays a crucial role in hormone-regulated plant development and holds promise for modulating SAS in agricultural contexts. 4-day-old dark-grown Col-0 seedlings were transferred to 1/2 MS liquid medium complemented with 30 μM PFT-α, 10 μM ACC or 1‰ DMSO (v/v) for 4 h, and whole seedlings were collected.Set three biological replicates for each treatment.