ELF3-PIF4 interaction regulates plant growth independently of the Evening Complex
Authors: Jean-Michel Davi√®re
Salom√© Prat
Cristina Nieto
Vadir L√≥pez-Salmer√≥n
Journal: Current Biology (2015)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: circadian clock; Arabidopsis; hypocotyl elongation; bHLH factors; PHYTOCHROME INTERACTING FACTOR 4
Affiliations: Departamento Gen√©tica Molecular de Plantas, Centro Nacional de Biotecnolog√≠a (CSIC), Campus de Cantoblanco, Darwin 3, 28049 Madrid, Spain., Departamento Gen√©tica Molecular de Plantas, Centro Nacional de Biotecnolog√≠a (CSIC), Campus de Cantoblanco, Darwin 3, 28049 Madrid, Spain. Electronic address: .

Abstract:  The circadian clock plays a pivotal role in the control of Arabidopsis hypocotyl elongation by regulating rhythmic expression of the bHLH factors PHYTOCHROME INTERACTING FACTOR 4 and 5 (PIF4 and 5). Coincidence of increased PIF4/PIF5 transcript levels with the dark period allows nuclear accumulation of these factors, and in short days it phases maximal hypocotyl growth at dawn. During early night, PIF4 and PIF5 transcription is repressed by the Evening Complex (EC) proteins EARLY FLOWERING3 (ELF3), EARLY FLOWERING4 (ELF4), and LUX ARRHYTHMO (LUX). While ELF3 has an essential role in EC complex assembly, several lines of evidence indicate that this protein controls plant growth via other mechanisms that are presently unknown. Here, we show that the ELF3 and PIF4 proteins interact in an EC-independent manner, and that this interaction prevents PIF4 from activating its transcriptional targets. We also show that PIF4 overexpression leads to ELF3 protein destabilization, and that this effect is mediated indirectly by negative feedback regulation of photoactive PHYTOCHROME B (phyB). Physical interaction of the phyB photoreceptor with ELF3 has been reported, but its functional relevance remains poorly understood. Our findings establish that phyB is needed for ELF3 accumulation in the light, most likely by competing for CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)-mediated ubiquitination and the proteasomal degradation of ELF3. Our results explain the short hypocotyl phenotype of ELF3 overexpressors, despite their normal clock function, and provide a molecular framework for understanding how warm temperatures promote hypocotyl elongation and affect the endogenous clock. 

Retracted: No

PubPeer comments:
 In Figure 1A, some panels seem duplicated.  , 
 We checked the original pictures taken from the plates and indeed drops corresponding to -LWHA were unintendly dulicated in -LW. In the initial Figure we were showing three different dilutions of the yeast cells but to make it simpler we decided to crop drops for the lower dilutions. During crop and pasting, the indicated pictures were duplicated by error and none of the authors realized of this mistake during revision of the work (the Figure is shown in the manuscript at a much lower magnification). We will inform Curr Biol about this problem for correction. We really regret that this sad mistake may induce readers to think that this interaction is shaky, since it was reproduced in independent Y2H studies and further confirmed in the rest of the manuscript, besides being subsequently ratified by studies carried out by other groups. , 
 From the  Author Contributions section, if this can help. V.L.-S. and J.-M.D. discovered direct interaction of ELF3 and PIF4 and performed yeast 2H, coIP, and BiFC studies. If you plan to correct this paper, please also double check and correct the supplemental data section. , 
 #2 I independently found the issues reported in comment #1. Could the authors please provide an update on status of the correction?  ,