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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]
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 ...
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 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 conception of the plant biological clock as made up of interacting negative feedback loops is unique in comparison to mammal and fungal circadian clocks which contain autoregulatory negative feedback loops with positive and negative elements [6] (see "Transcriptional and non-transcriptional control on the Circadian clock page).
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 ...
Webb's research surrounding the model organism, Arabidopsis thaliana, has demonstrated that photosynthetic cues are responsible for maintaining and entraining the endogenous clocks of plants. [ 4 ] [ 5 ] [ 6 ] Specifically, his early research demonstrates that plants' circadian rhythms control the daily opening of the stomata and nightly ...