Control of adventitious rooting by TIR1/AFB2-Aux/IAA-dependent auxin signaling ($) (Mol Plant)

Adventitious roots typically develop from non-root tissue like shoots either naturally in some species or upon induction by stress in most species. The key roles of auxin signaling in lateral root development are well known but the role of these regulators in adventitious roots with their high phenotypic plasticity is still unknown. In this paper, Lakehal et al. have identified that during adventitious root formation, TIR1and AFB2 (TRANSPORT INHIBITOR1/AUXIN_SIGNALLING F_BOX2) of the auxin signaling pathway interact with each other and activate ARF6 and/or ARF8 (AUXIN RESPONSE FACTOR) to regulate the expression of specific GH3 (GRETCHEN HAGEN 3) genes, which in addition to inactivating IAA also inactivate jasmonic acid (JA), an inhibitor of AR initiation in Arabidopsis hypocotyls. Through genetic knockdown, the authors showed that IAA6, IAA9, and IAA17 also participate in auxin signaling, and the loss-of-function alleles of these regulators cause a significant increase in adventitious root formation and change the expression of GH3.3, GH3.5, and GH3.6. The authors propose a molecular framework involving auxin – jasmonic acid regulation of adventitious root development in Arabidopsis. (Summary by Suresh Damodaran) Mol. Plant 10.1016/j.molp.2019.09.001