PCH1 integrates circadian and light-signaling pathways to control photoperiod-responsive growth in Arabidopsis.

He Huang,Bradley S Evans,Jessica Goldsworthy,Sophie Alvarez,Rebecca Bindbeutel,Dmitri A Nusinow,Meng Chen,Chan Yul Yoo,Allison Tielking,Michael J Naldrett

doi:10.7554/elife.13292

Abstract

Plants react to seasonal change in day length through altering physiology and development. Factors that function to harmonize growth with photoperiod are poorly understood. Here we characterize a new protein that associates with both circadian clock and photoreceptor components, named PHOTOPERIODIC CONTROL OF HYPOCOTYL1 (PCH1). pch1 seedlings have overly elongated hypocotyls specifically under short days while constitutive expression of PCH1 shortens hypocotyls independent of day length. PCH1 peaks at dusk, binds phytochrome B (phyB) in a red light-dependent manner, and co-localizes with phyB into photobodies. PCH1 is necessary and sufficient to promote the biogenesis of large photobodies to maintain an active phyB pool after light exposure, potentiating red-light signaling and prolonging memory of prior illumination. Manipulating PCH1 alters PHYTOCHROME INTERACTING FACTOR 4 levels and regulates light-responsive gene expression. Thus, PCH1 is a new factor that regulates photoperiod-responsive growth by integrating the clock with light perception pathways through modulating daily phyB-signaling.

Highlights

Plants have evolved to coordinate physiology and phenology with seasonal variation in the environment (Wilczek et al, 2010)
A protein encoded by At2g16365, a gene that was described as required for transcriptional responses to lincomycin-induced chloroplast damage (Ruckle et al, 2012), was repeatedly co-purified with the EC by tandem affinity-purification coupled with mass spectrometry (AP-MS) analyses (Huang et al, 2015)
We show that PHOTOPERIODIC CONTROL OF HYPOCOTYL1 (PCH1) is a new phytochrome interacting protein that functions to increase sensitivity to red light and prolongs phytochrome B (phyB) activity by maintaining photobody formation

Summary

Introduction

Plants have evolved to coordinate physiology and phenology with seasonal variation in the environment (Wilczek et al, 2010). These adaptations to changing day length are called photoperiodic responses, which are regulated by both the circadian clock and specific signaling pathways, including light sensory systems (Shim and Imaizumi, 2015). In Arabidopsis, daily hypocotyl elongation is accelerated in short days compared to long day conditions, and requires both the circadian clock and light signals to properly react to changing photoperiods (Niwa et al, 2009; Nozue et al, 2007).

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