The ELF4–ELF3–LUX complex links the circadian clock to diurnal control of hypocotyl growth

• Published in: Nature (London) Vol. 475; no. 7356; pp. 398 - 402
• Main Authors: Nusinow, Dmitri A., Helfer, Anne, Hamilton, Elizabeth E., King, Jasmine J., Imaizumi, Takato, Schultz, Thomas F., Farré, Eva M., Kay, Steve A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21-07-2011; Nature Publishing Group
• Subjects: 631/449/1659; 631/449/448/1384; 631/45/612; Amino acids; Arabidopsis - cytology; Arabidopsis - growth & development; Arabidopsis - physiology; Arabidopsis - radiation effects; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Basic Helix-Loop-Helix Transcription Factors - deficiency; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Biological and medical sciences; Circadian Clocks - physiology; Circadian Clocks - radiation effects; Circadian rhythm; Circadian Rhythm - physiology; Circadian Rhythm - radiation effects; Circadian rhythms; DNA binding proteins; Educational psychology; Environmental changes; Environmental conditions; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant; Genetic aspects; Growth; Humanities and Social Sciences; Hypocotyl - cytology; Hypocotyl - growth & development; Hypocotyl - radiation effects; letter; Light; Molecular weight; multidisciplinary; Multiprotein Complexes - chemistry; Multiprotein Complexes - metabolism; Mutation; Physiological aspects; Plant growth; Protein Binding; Proteins; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Pupil and student. Academic achievement and failure; Science; Science (multidisciplinary); Transcription Factors - metabolism; Two-Hybrid System Techniques; Yeast; United States; United Kingdom; Human; Acquisition process; Structuration; University; Sciences; Biology; Academic learning; Student
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature10182

The evening routine
In plants, the circadian clock functions as an endogenous pacemaker that anticipates and responds to a changing environment in order to optimize the timing of physiological and developmental events. Nusinow
et al
. elucidate the mechanism by which the circadian clock controls growth of the model plant
Arabidopsis thaliana
. A novel trimeric complex called the evening complex is regulated by the clock and has a peak of expression at dusk. The complex represses the expression of two transcription factors, PIF4 and PIF5, which are part of a light-signalling cascade that controls the timing of plant growth in response to light conditions.
The circadian clock is required for adaptive responses to daily and seasonal changes in environmental conditions
1
,
2
,
3
. Light and the circadian clock interact to consolidate the phase of hypocotyl cell elongation to peak at dawn under diurnal cycles in
Arabidopsis thaliana
4
,
5
,
6
,
7
. Here we identify a protein complex (called the evening complex)—composed of the proteins encoded by
EARLY FLOWERING 3
(
ELF3
),
ELF4
and the transcription-factor-encoding gene
LUX ARRHYTHMO
(
LUX
; also known as
PHYTOCLOCK 1
)—that directly regulates plant growth
8
,
9
,
10
,
11
,
12
. ELF3 is both necessary and sufficient to form a complex between ELF4 and LUX, and the complex is diurnally regulated, peaking at dusk.
ELF3
,
ELF4
and
LUX
are required for the proper expression of the growth-promoting transcription factors encoded by
PHYTOCHROME INTERACTING FACTOR 4
(
PIF4
) and
PIF5
(also known as
PHYTOCHROME INTERACTING FACTOR 3-LIKE 6
) under diurnal conditions
4
,
6
,
13
. LUX targets the complex to the promoters of
PIF4
and
PIF5 in vivo
. Mutations in
PIF4
and/or
PIF5
are epistatic to the loss of the ELF4–ELF3–LUX complex, suggesting that regulation of
PIF4
and
PIF5
is a crucial function of the complex. Therefore, the evening complex underlies the molecular basis for circadian gating of hypocotyl growth in the early evening.