ETHYLENE INSENSITIVE 3 suppresses plant de novo root regeneration from leaf explants and mediates age-regulated regeneration decline.

Powerful regeneration ability enables plant survival when plants are wounded. For example, adventitious roots can regenerate from the cutting site in detached Arabidopsis thaliana leaf explants, even in the absence of any exogenous plant hormone treatment. This process is known as de novo root regeneration (DNRR). Although the developmental program underlying DNRR is known, the precise regulatory mechanisms underlying DNRR are not completely understood. Here, we show that ethylene treatment or genetic activation of transcription factor ETHYLENE INSENSITIVE 3 (EIN3) strongly suppresses DNRR rates, while a mutant lacking EIN3 and its homolog EIL1 (ein3 eil1) displays a higher DNRR capacity. Previous reports have shown that the sequential induction of WUSCHEL RELATED HOMEOBOX 11 (WOX11)/WOX12 and WOX5/WOX7 expression is required for the establishment of DNRR. We found that EIN3 directly targets WOX11 and WOX5 promoter regions to suppress their transcription. Furthermore, older plants show enhanced EIN3 activity, and repressed expression of WOX11 and WOX5 Taken together, these results illustrate that plant aging at least partially takes advantage of EIN3 as a negative regulator to suppress DNRR through inhibiting the activation of WOX genes.