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. 2018 Apr 2;11(4):523-541.
doi: 10.1016/j.molp.2017.12.003. Epub 2017 Dec 19.

Photoactivated CRY1 and phyB Interact Directly With AUX/IAA Proteins to Inhibit Auxin Signaling in Arabidopsis

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Photoactivated CRY1 and phyB Interact Directly With AUX/IAA Proteins to Inhibit Auxin Signaling in Arabidopsis

Feng Xu et al. Mol Plant. .
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Abstract

Light is a key environmental cue that inhibits hypocotyl cell elongation through the blue and red/far-red light photoreceptors cryptochrome- and phytochrome-mediated pathways in Arabidopsis. In contrast, as a pivotal endogenous phytohormone auxin promotes hypocotyl elongation through the auxin receptors TIR1/AFBs-mediated degradation of AUX/IAA proteins (AUX/IAAs). However, the molecular mechanisms underlying the antagonistic interaction of light and auxin signaling remain unclear. Here, we report that light inhibits auxin signaling through stabilization of AUX/IAAs by blue and red light-dependent interactions of cryptochrome 1 (CRY1) and phytochrome B with AUX/IAAs, respectively. Blue light-triggered interactions of CRY1 with AUX/IAAs inhibit the associations of TIR1 with AUX/IAAs, leading to the repression of auxin-induced degradation of these proteins. Our results indicate that photoreceptors share AUX/IAAs with auxin receptors as the same direct downstream signaling components. We propose that antagonistic regulation of AUX/IAA protein stability by photoreceptors and auxin receptors allows plants to balance light and auxin signals to optimize their growth.

Keywords: AUX/IAA proteins; Arabidopsis; auxin; cryptochrome; light; phytochrome.

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