Abstract

In Arabidopsis thaliana, canonical auxin-dependent gene regulation is mediated by 23 transcription factors from the AUXIN RESPONSE FACTOR (ARF) family that interact with auxin/indole acetic acid repressors (Aux/IAAs), which themselves form co-receptor complexes with one of six TRANSPORT INHIBITOR1/AUXIN-SIGNALLING F-BOX (TIR1/AFB) proteins. Different combinations of co-receptors drive specific sensing outputs, allowing auxin to control a myriad of processes. ARF6 and ARF8 are positive regulators of adventitious root initiation upstream of jasmonate, but the exact auxin co-receptor complexes controlling the transcriptional activity of these proteins has remained unknown. Here, using loss-of-function mutants we show that three Aux/IAA genes, IAA6, IAA9, and IAA17, act additively in the control of adventitious root (AR) initiation. These three IAA proteins interact with ARF6 and/or ARF8 and likely repress their activity in AR development. We show that TIR1 and AFB2 are positive regulators of AR formation and TIR1 plays a dual role in the control of jasmonic acid (JA) biosynthesis and conjugation, as several JA biosynthesis genes are up-regulated in the tir1-1 mutant. These results lead us to propose that in the presence of auxin, TIR1 and AFB2 form specific sensing complexes with IAA6, IAA9, and/or IAA17 to modulate JA homeostasis and control AR initiation.

Keywords

TIR1/AFB; AuxIAA; jasmonate; adventitious roots; Arabidopsis

Published in

Molecular Plant
2019, Volume: 12, number: 11, pages: 1499-1514
Publisher: CELL PRESS

SLU Authors

• Novak, Ondrej

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    
  • Palacký University Olomouc

UKÄ Subject classification

Cell and Molecular Biology


Publication identifier

DOI: https://doi.org/10.1016/j.molp.2019.09.001

Permanent link to this page (URI)

https://res.slu.se/id/publ/102751