14-3-3 λ suppresses ethylene-mediated root growth inhibition through EIN3/EIL1 in Arabidopsis

Plant roots explore the soil in search of water and nutrients essential for growth. ETHYLENE INSENSITIVE 3 (EIN3) and EIN3-LIKE 1 (EIL1), the central transcription factors in the ethylene signaling pathway, orchestrate a wide range of developmental and stress-responsive processes, including root growth; however, how transcriptional activation of EIN3/EIL1 is regulated remains to be elucidated. Here, we show that the Arabidopsis (Arabidopsis thaliana) regulatory protein 14-3-3 λ, a member of the evolutionarily conserved 14-3-3 protein family, physically interacts with EIN3/EIL1 to attenuate their transcriptional activity, thereby repressing ethylene-mediated inhibition of primary root elongation. Loss of 14-3-3 λ confers hypersensitivity to 1-aminocyclopropane-1-carboxylic acid (ACC), and this phenotype is suppressed by ein3/eil1 mutations. Notably, ACC treatment promotes the translocation of 14-3-3 λ from the nucleus to the cytosol, which weakens the interaction between 14-3-3 λ and EIN3/EIL1, relieving repression of EIN3/EIL1 transcriptional activity in plants. Collectively, these findings reveal that 14-3-3 λ dampens the ethylene response by binding to and inhibiting EIN3/EIL1. ACC disrupts this interaction, releasing EIN3/EIL1 to activate ethylene signaling and consequently inhibiting primary root elongation.