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Circadian Clock Associated 1 (CCA1) is a gene that is central to the circadian oscillator of angiosperms. It was first identified in Arabidopsis thaliana in 1993. CCA1 interacts with LHY and TOC1 to form the core of the oscillator system.
CAB is confined to the mesophyll and guard cells and the cycling of CAB expression in the Arabidopsis plant suggests that there is a circadian clock that controls the CAB gene. [ 16 ] [ 17 ] When the plants were moved from light/dark cycles to constant darkness, CAB2 and CAB3 genes showed an exaggerated circadian cycling. [ 17 ]
The circadian clock in plants has completely different components to those in the animal, fungus or bacterial clocks. The plant clock does have a conceptual similarity to the animal clock in that it consists of a series of interlocking transcriptional feedback loops. The genes involved in the clock show their peak expression at a fixed time of day.
The first TTFL model was proposed for Arabidopsis thaliana in 2001 and included two MYB transcription factors, LATE ELONGATED HYPOCOTYL (LHY), CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), and TIMING OF CAB EXPRESSION 1 (TOC1). CCA1 and LHY are expressed in the morning, and interact together to repress the expression of TOC1.
The morning loop consists of CCA1 (Circadian and Clock-Associated 1) and LHY (Late Elongated Hypocotyl), which encode closely related MYB transcription factors that regulate circadian rhythms in Arabidopsis, as well as PRR 7 and 9 (Pseudo-Response Regulators.) The evening loop consists of GI (Gigantea) and ELF4, both involved in regulation of ...
Though their research that discovered PRR genes was primarily hailed during the early 2000s as informing the scientific community about the function of TOC1 (named APRR1 by the Mizuno lab), an additional pseudo-response regulator in the Arabidopsis thaliana biological clock, [3] the information about PRR genes that Matsushika and his team found ...
Arabidopsis plants to which varying amounts of ABA were applied showed corresponding differences in TOC1 expression and in circadian period length. Through computational modeling of this feedback loop, TOC1 was shown to be a clock-based influence on patterns of stoma opening and closure, which has traditionally been described as a mainly ABA ...
Cryptochromes are classified into plant Cry and animal Cry. Animal Cry can be further categorized into insect type (Type I) and mammal-like (Type II). CRY1 is a circadian photoreceptor whereas CRY2 is a clock repressor which represses Clock/Cycle (Bmal1) complex in insects and vertebrates. [4]