There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
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.