Biological clockAn innate mechanism in living organisms that controls the periodicity or rhythm of various physiological functions or activities.

– Circadian rhythm• Circadian: circa(around)+dies(day)

– Ultradian rhythm– Infradian rhythm

Internal biological clock+ change of environment

Reset / entrainment mechanism

Clock-associated genes

• CCA1• LHY• FKF1• ZTL

Environments

• Temperature

• Light– Period– wave

Relationship clock-associated genes and the photoreceptors

ELF3 Encodes a Circadian Clock-Regulated Nuclear Protein That

Functions in an Arabidopsis PHYB Signal Transduction Pathway

elf3

• Defective in light perception or light-mediated signal transduction

• Defective in circadian rhythm responses

wild(C)

elf3-1

elf3-1:cosmid B8

elf3-1:cosmid E11

SD

LDLD

SD

Two types of photoreceptor

• Five red/far-red light-absorbing phytochromes– Phytochrome A[PHYA], PHYB, PHYC,

PHYD, and PHYE

• Two blue/UV-A light-absorbing cryptochromes– CRY1 and CRY2

ELF3

• novel 695 amino acid protein• without any significant homology to

proteins of known function• glutamine/threonine-rich sequence

and nuclear localization signal in the C-terminal region

transcription factor

Fig 1-A. Sequence comparison of ELF3 and putative ELF3 homologs

Cardamine

Arabidopsis

tomatoricemaize

ELF3 function may be conserved between dicots and monocots.

Fig 1-B. ELF3 is a novel nuclear protein.

Fig 2. Accumulation of the ELF3 protein is regulated by light and the circadian clock.

Fig 3-1. ELF3 and PHYB proteins interaction in the Yeast Tow-Hybrid System

Fig 3-2. ELF3 and PHYB proteins interaction in Vitro

PHYB-ELF3 interaction in vivo could regulate aspects of PHYB-mediated photomorphogenesis

Fig 4-A. Hypocotyl length of seedlings grown under dark, white, red, and far-red light condition.

Fig 4-B Flowering time for wild type and mutant plants under LD or SD growth conditions.

Fig 5. Genetic interactions of the ELF3 overexpression(ELF3-OX) line with the phyB mutation