Synthetically derived BiAux modulates auxin co-receptor activity to stimulate lateral root formation

• Published in: Plant physiology (Bethesda) Vol. 195; no. 2; pp. 1694 - 1711
• Main Authors: González-García, Mary Paz, Sáez, Angela, Lanza, Mónica, Hoyos, Pilar, Bustillo-Avendaño, Estefano, Pacios, Luis F, Gradillas, Ana, Moreno-Risueno, Miguel A, Hernaiz, María José, Del Pozo, Juan C
• Format: Journal Article
• Language: English
• Published: United States 31.05.2024
• Subjects: Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; F-Box Proteins - genetics; F-Box Proteins - metabolism; Gene Expression Regulation, Plant; Indoleacetic Acids - metabolism; Plant Growth Regulators - metabolism; Plant Roots - genetics; Plant Roots - growth & development; Plant Roots - metabolism; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Signal Transduction
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1093/plphys/kiae090

The root system plays an essential role in plant growth and adaptation to the surrounding environment. The root clock periodically specifies lateral root prebranch sites (PBS), where a group of pericycle founder cells (FC) is primed to become lateral root founder cells and eventually give rise to lateral root primordia or lateral roots (LRs). This clock-driven organ formation process is tightly controlled by modulation of auxin content and signaling. Auxin perception entails the physical interaction of TRANSPORT INHIBITOR RESPONSE 1 (TIR1) or AUXIN SIGNALING F-BOX (AFBs) proteins with AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) repressors to form a co-receptor system. Despite the apparent simplicity, the understanding of how specific auxin co-receptors are assembled remains unclear. We identified the compound bis-methyl auxin conjugated with N-glucoside, or BiAux, in Arabidopsis (Arabidopsis thaliana) that specifically induces the formation of PBS and the emergence of LR, with a slight effect on root elongation. Docking analyses indicated that BiAux binds to F-box proteins, and we showed that BiAux function depends on TIR1 and AFB2 F-box proteins and AUXIN RESPONSE FACTOR 7 activity, which is involved in FC specification and LR formation. Finally, using a yeast (Saccharomyces cerevisiae) heterologous expression system, we showed that BiAux favors the assemblage of specific co-receptors subunits involved in LR formation and enhances AUXIN/INDOLE-3-ACETIC ACID 28 protein degradation. These results indicate that BiAux acts as an allosteric modulator of specific auxin co-receptors. Therefore, BiAux exerts a fine-tune regulation of auxin signaling aimed to the specific formation of LR among the many development processes regulated by auxin.