Depletion of Gibberellin Signaling Accelerates De Novo Root Regeneration in Arabidopsis thaliana, Which Can Rescue Declined Adventitious Root Formation from Erecta Mutant Leaf Explants

Adventitious root (AR) formation in plants origins from non-root organs such as leaves and hy-pocotyls. Auxin signaling is essential for AR formation, but the role of other phytohormones is less clear. In Arabidopsis, at least two distinct mechanisms can produce ARs either from hypocotyls as part of the general root architecture, or from wounded organs during de novo root regeneration (DNRR). In previous reports, gibberellin acid (GA) seems to play reverse roles in both types of AR formation, since GA treatment blocks AR formation from hypocotyls, whereas depletion of GA signaling results in reduced DNRR from detached leaves. Here, we report the positive effects of GA biosynthesis inhibitor paclobutrazol (PBZ/PAC) treatment on both types of AR formation in Arabidopsis. Consistently, loss of GA synthesis and signaling promoted DNRR in our conditions. Furthermore, PBZ treatment can rescue declined AR formation from leaf explants in erecta recep-tor mutants. Transcriptional profiling revealed that PBZ treatment altered GA, brassinosteroids and auxin responses, which included up-regulation of LBD16 that plays a pivotal role in AR initi-ation. This study reveals that depletion of GA biosynthesis promotes DNRR in Arabidopsis, and thus will contribute to further clarification of the role of GA during AR formation in plants.