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 the 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.

Multi-walled carbon nanotubes (MWCNTs) can modulate plant growth and development, but the signaling mechanisms underlying their effects on organogenesis remain unclear. Here, we found that MWCNTs promote adventitious root (AR) formation and that RBOH-dependent hydrogen peroxide (H₂O₂) production plays a key role in this process in cucumber (Cucumis sativus L.) and Arabidopsis thaliana. MWCNTs treatment promoted AR formation in cucumber hypocotyls. Concomitantly, endogenous H₂O₂ levels increased rapidly, along with enhanced CsRBOHD expression and NADPH oxidase activity, suggesting activation of an RBOH-dependent H₂O₂ response. Consistent with this, scavenging H₂O₂ or inhibiting NADPH oxidase markedly reduced MWCNTs-induced rooting, whereas exogenous H₂O₂ partially restored AR formation under NADPH oxidase inhibition. Genetic evidence further supported this relationship, as Atrbohd and Atrbohf mutants showed reduced responses to MWCNTs but remained responsive to exogenous H₂O₂, suggesting that RBOH-mediated H₂O₂ generation is a critical step in MWCNTs-induced adventitious rooting. In parallel, MWCNTs and H₂O₂ treatments enhanced the expression of genes associated with adventitious root development. Together, these findings support a model in which MWCNTs promote adventitious rooting through RBOH-dependent H₂O₂ signaling, providing new insight into nanomaterial-mediated regulation of plant development.