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Related Concept Videos

Biological Clocks and Seasonal Responses02:45

Biological Clocks and Seasonal Responses

The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
Circadian Rhythms and Gene Regulation02:19

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Cell Signaling in Plants01:25

Cell Signaling in Plants

Plant cells communicate to coordinate their cycle of growth, flowering and fruiting, and activities in roots, shoots, and leaves in response to the changing environmental conditions. Plant signaling is distinct from animal signaling. Plants primarily utilize enzyme-linked receptors, whereas the largest class of cell-surface receptors in animals are G-protein coupled receptors (GPCRs). Unlike animals, receptor tyrosine kinases are rare in plants. Instead, plants have a diverse class of...
Photoreceptors and Plant Responses to Light02:00

Photoreceptors and Plant Responses to Light

Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.
C4 Pathway and CAM01:27

C4 Pathway and CAM

Most plants use the C3 pathway for carbon fixation. However, some plants, such as sugar cane, corn, and cacti that grow in hot conditions, use alternative pathways to fix carbon and conserve energy loss due to photorespiration. Photorespiration is the process that occurs when the oxygen concentration is high. Under such conditions, the rubisco enzyme in the Calvin cycle binds O2 instead of CO2, which halts photosynthesis and consumes energy.
C4 Pathway
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Rapid Analysis of Circadian Phenotypes in Arabidopsis Protoplasts Transfected with a Luminescent Clock Reporter
07:42

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Published on: September 17, 2016

Are there multiple circadian clocks in plants?

Carlos T Hotta1, Xiaodong Xu, Qiguang Xie

  • 1Department of Plant Sciences; University of Cambridge; Cambridge, United Kingdom.

Plant Signaling & Behavior
|October 21, 2009
PubMed
Summary

Arabidopsis has distinct cell-type circadian clocks. Light affects CHLOROPHYLL A/B BINDING PROTEIN2 (CAB2) rhythms and calcium oscillations differently, revealing complex regulation of these core biological processes.

Keywords:
CAB2Ca2+ signallingTOC1aequorinarabidopsiscentral oscillatorcircadian [Ca2+]cyt oscillationscircadian rhythmsluciferasemultiple oscillators

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Area of Science:

  • Plant Biology
  • Chronobiology
  • Molecular Genetics

Background:

  • Arabidopsis thaliana may possess genetically distinct circadian oscillators within different cell types.
  • Circadian rhythms of CHLOROPHYLL A/B BINDING PROTEIN2 (CAB2) promoter activity and cytosolic free Ca(2+) ([Ca(2+)](cyt)) oscillations are key indicators of the plant circadian clock.

Purpose of the Study:

  • To investigate the potential genetic distinctness of circadian oscillators in different Arabidopsis cell types.
  • To analyze the differential regulation of CAB2 promoter activity rhythms and [Ca(2+)](cyt) oscillations in various circadian mutants.

Main Methods:

  • Phenotypic analysis of circadian rhythms in Arabidopsis mutants under different light conditions.
  • Measurement of CAB2 promoter activity and [Ca(2+)](cyt) oscillations in wild-type and mutant lines.

Main Results:

  • Mutants in phytochromeB and cryptochrome1 cry2 exhibited altered CAB2 promoter activity rhythms but lacked [Ca(2+)](cyt) oscillations.
  • CIRCADIAN CLOCK ASSOCIATED1 (CCA1) mutants showed short period leaf movement rhythms but arrhythmic [Ca(2+)](cyt) oscillations.
  • The toc1-1 mutant displayed short period CAB2 rhythms but wild-type period [Ca(2+)](cyt) oscillations, contrasting with the toc1-2 loss-of-function mutant which had short periods for both.

Conclusions:

  • CAB2 promoter activity and [Ca(2+)](cyt) oscillations are regulated by distinct mechanisms within the Arabidopsis circadian system.
  • The differential phenotypes of toc1-1 and toc1-2 mutants highlight the complex roles of TOC1 in circadian rhythmicity.
  • Evidence suggests cell-type specific regulation of circadian outputs in response to light signaling pathways.