Arabidopsis Hypocotyl Adventitious Root Formation Is Suppressed by ABA Signaling

Roots are composed of different root types and, in the dicotyledonous Arabidopsis, typically consist of a primary root that branches into lateral roots. Adventitious roots emerge from non-root tissue and are formed upon wounding or other types of abiotic stress. Here, we investigated adventitious root (AR) formation in Arabidopsis hypocotyls under conditions of altered abscisic acid (ABA) signaling. Exogenously applied ABA suppressed AR formation at 0.25 mu M or higher doses. AR formation was less sensitive to the synthetic ABA analog pyrabactin (PB). However, PB was a more potent inhibitor at concentrations above 1 mu M, suggesting that it was more selective in triggering a root inhibition response. Analysis of a series of phosphonamide and phosphonate pyrabactin analogs suggested that adventitious root formation and lateral root branching are differentially regulated by ABA signaling. ABA biosynthesis and signaling mutants affirmed a general inhibitory role of ABA and point to PYL1 and PYL2 as candidate ABA receptors that regulate AR inhibition.

Automated summary

The study found that exogenously applied ABA can suppress the formation of adventitious roots in Arabidopsis, while the synthetic ABA analog PB exhibits a stronger inhibitory effect. Additionally, analysis of various pyrabactin analogs suggests that adventitious root formation and lateral root branching are regulated differently by ABA signaling, with PYL1 and PYL2 identified as candidate ABA receptors that control AR inhibition.