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.

在拟南芥中，典型的生长素依赖性基因调控是由来自AUXIN RESPONSE FACTOR（ARF）家族的23个转录因子介导的，这些转录因子与生长素/吲哚乙酸阻遏物（Aux / IAA）相互作用，它们本身与以下一种形成共受体复合物六种运输抑制剂/ AUXIN信号传递F-BOX（TIR1 / AFB）蛋白。共受体的不同组合驱动特定的传感输出，从而使生长素能够控制无数的过程。ARF6和ARF8是茉莉酸酯上游不定根起始的正向调节剂，但是控制这些蛋白转录活性的生长素共受体复合物的确切作用仍然未知。在这里，使用功能丧失的突变体，我们显示了三个Aux / IAA基因IAA6，IAA9和IAA17在不定根（AR）引发的控制中起附加作用。这三种IAA蛋白与ARF6和/或ARF8相互作用，并可能抑制其在AR发育中的活性。我们显示，TIR1和AFB2是AR形成的正调节剂，并且TIR1在茉莉酸（JA）生物合成和缀合的控制中起着双重作用，因为一些JA生物合成基因在tir1-1突变体中被上调。这些结果使我们建议，在生长素存在的情况下，TIR1和AFB2与IAA6，IAA9和/或IAA17形成特定的感官复合物，从而调节JA稳态并控制AR的启动。