Biological clock An innate mechanism in living organisms that controls the periodicity or rhythm of...

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