Cytokinin response factors regulate PIN-FORMED auxin transporters.

Mária Šimášková,Giel Van Noorden,Peter Marhavý,Mamoona Khan,Frank Van Breusegem,Krisztina Ötvös,José Antonio O’Brien,Johanna Maria Adriana Van Haperen,Tom Beeckman,Inge De Clercq,Krzysztof Wabnik,Dolf Weijers,Candela Cuesta,Klára Hoyerová,Eva Benková,Steffen Vanneste,Anne Vieten,Moritz K Nowack ,Jiřı́ Friml ,Angus S Murphy

doi:10.1038/ncomms9717

Abstract

Auxin and cytokinin are key endogenous regulators of plant development. Although cytokinin-mediated modulation of auxin distribution is a developmentally crucial hormonal interaction, its molecular basis is largely unknown. Here we show a direct regulatory link between cytokinin signalling and the auxin transport machinery uncovering a mechanistic framework for cytokinin-auxin cross-talk. We show that the CYTOKININ RESPONSE FACTORS (CRFs), transcription factors downstream of cytokinin perception, transcriptionally control genes encoding PIN-FORMED (PIN) auxin transporters at a specific PIN CYTOKININ RESPONSE ELEMENT (PCRE) domain. Removal of this cis-regulatory element effectively uncouples PIN transcription from the CRF-mediated cytokinin regulation and attenuates plant cytokinin sensitivity. We propose that CRFs represent a missing cross-talk component that fine-tunes auxin transport capacity downstream of cytokinin signalling to control plant development.

Highlights

Auxin and cytokinin are key endogenous regulators of plant development
We confirmed that the promoter (1,423 bp upstream of the translational start site) of PIN7 fused to the green fluorescent protein (GFP) reporter gene (Supplementary Fig. 1a) is activated by cytokinin and that this region is sufficient to mediate the hormonal response (Fig. 1a)
The role of this regulatory element, designated as PCRE7, in cytokinin-sensitive expression was further tested with a PIN7–GFP translational construct driven by the truncated DPIN7 promoter

Summary

Introduction

Auxin and cytokinin are key endogenous regulators of plant development. cytokinin-mediated modulation of auxin distribution is a developmentally crucial hormonal interaction, its molecular basis is largely unknown. We show that the CYTOKININ RESPONSE FACTORS (CRFs), transcription factors downstream of cytokinin perception, transcriptionally control genes encoding PIN-FORMED (PIN) auxin transporters at a specific PIN CYTOKININ RESPONSE ELEMENT (PCRE) domain Removal of this cis-regulatory element effectively uncouples PIN transcription from the CRF-mediated cytokinin regulation and attenuates plant cytokinin sensitivity. We show that the cytokinin response factors (CRFs)[21] transcriptionally control PIN-FORMED (PIN) genes encoding auxin transporters at a specific PIN CYTOKININ RESPONSE ELEMENT (PCRE) domain Removal of this cis-regulatory element effectively uncouples PIN transcription from the CRFdependent regulation and attenuates plant cytokinin sensitivity. We propose that the CRFs act as components of the transcriptional regulatory complex, which mediates transcriptional control downstream of cytokinin and fine-tunes PIN expression during plant growth and development

Methods

Results

Conclusion