Arabidopsis Transcription Factor TCP5 Controls Plant Thermomorphogenesis by Positively Regulating PIF4 Activity

Xiang Han,Hao Yu,Rongrong Yuan,Yan Yang,Fengying An,Genji Qin

doi:10.1016/j.isci.2019.04.005

Abstract

SummaryPlants display thermomorphogenesis in response to high temperature (HT). PHYTOCHROME INTERACTING FACTOR 4 (PIF4) is a central integrator regulated by numerous negative regulators. However, the mechanisms underpinning PIF4 positive regulation are largely unknown. Here, we find that TEOSINTE BRANCHED 1/CYCLOIDEA/PCF 5 (TCP5), TCP13, and TCP17 transcription factors promote the activity of PIF4 at transcriptional and post-transcriptional levels. TCP5 is rapidly induced by HT treatment, and TCP5 protein stability increases under HT. The overexpression of TCP5 causes constitutive thermomorphogenic phenotypes, whereas the tcp5 tcp13 tcp17 triple mutant exhibits aberrant thermomorphogenesis. We demonstrate that TCP5 not only physically interacts with PIF4 to enhance its activity but also directly binds to the promoter of PIF4 to increase its transcript. TCP5 and PIF4 share common downstream targets. The tcp5 tcp13 tcp17 mutant partially restores the long hypocotyls caused by PIF4 overexpression. Our findings provide a layer of understanding about the fine-scale regulation of PIF4 and plant thermomorphogenesis.

Highlights

The strong 2018 summer heat waves across the Northern Hemisphere caused a high temperature (HT) of up to 30C in some areas of the Arctic Circle and severe losses in crop production
TEOSINTE BRANCHED 1/CYCLOIDEA/PCF 5 (TCP5) Positively Regulates Plant Thermomorphogenesis We previously found that the overexpression of TCP5 leads to aborted ovules (Wei et al, 2015)
To test whether TCP13 and TCP17 could be functionally redundant with TCP5, we overexpressed TCP13 or TCP17 using the Cauliflower Mosaic Virus (CaMV) 35S promoter and found that both 35Spro-TCP13 and 35Spro-TCP17 transgenic plants exhibited longer hypocotyls at 20C and 28C, resembling the constitutive thermomorphogenesis observed in 35Spro-TCP5 plants (Figures 1A and 1B)

Summary

Introduction

The strong 2018 summer heat waves across the Northern Hemisphere caused a high temperature (HT) of up to 30C in some areas of the Arctic Circle and severe losses in crop production. BLADE-ON-PETIOLE (BOP) proteins, a component of CUL3BOP1/BOP2 (CULLIN3ABOP1/BOP2) E3 ubiquitin ligase complex, have been reported to mediate PIF4 degradation (Zhang et al, 2017). Several proteins, such as CRYPTOCHROME 1 (CRY1) (Ma et al, 2016), LONG HYPOCOTYL IN FAR-RED 1 (HFR1) (Foreman et al, 2011), and ELF3 (Box et al, 2015), repress PIF4 transcriptional activity by directly interacting with PIF4.

Methods

Results

Conclusion