植物生物钟课件
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Gene transcript abundance
The feedback loop results in rhythms of transcript abundance of the two genes
Gene A
Gene B
Gene A
Protein B
Gene B
0
12
24 36 Time (hours)
Overexpression of TOC1 suppresses circadian oscillations of CCA1
The CCT domain of TOC1 is required for it to bind the CCA1 promoter
From Alabadı́, D., Oyama, T., Yanovsky, M.J., Harmon, F.G., Má s, P. and Kay, S.A. (2001). Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock. Science. 293: 880-883. Reprinted with permission from AAAS. Gendron, J.M., Pruneda-Paz, J.L., Doherty, C.J., Gross, A.M., Kang, S.E. and Kay, S.A. (2012). Arabidopsis circadian clock protein, TOC1, is a DNA-binding transcription factor. Proc. Natl. Acad. Sci. USA 109: 3167-3172. © 2016 American Society of Plant Biologists
Rhythms of Life: The Plant Circadian Clock
Somers, D.E. (1999). The physiology and molecular bases of the plant circadian clock. Plant Physiol. 121: 9-20.
© 2016 American Society of Plant Biologists
Living on a rotating planet is biologically stressful
Over a 24 hour period there is large variation in environmental conditions including temperature, light intensity, humidity and predator behavior
© 2016 American Society of Plant Biologists
The circadian oscillator
Most circadian clocks are transcription-translation feedback loops
The protein encoded by Gene A activates Gene B
Image sources: H. Zell, Charles Darwin “Power of Movement in Plants”
© 2016 American Society of Plant Biologists
Architecture of the circadian clock
© 2016 American Society of Plant Biologists
Adjust the sensitivity of entrainment and output pathways depending on the time of day
© 2016 American Society of Plant Biologists
Interconnected parts of the circadian system
• Extreme day-night temperature difference: 57 oC (-48 oC to 9 oC, Montana, 1972) • Typical day-night fluctuation: ~10 oC each day (central Japan)
See Kudoh, H. (2016). Molecular phenology in plants: in natura systems biology for the comprehensive understanding of seasonal responses under natural environments. New Phytol. 210: 399-412. Image: NASA.
48
• Reciprocal feedback loop • Negative feedback step • Speed of biochemical reactions adds a rate constant
Simple biological oscillator
© 2016 American Society of Plant Biologists
22.30 Bowel movements suppressed
Image source: Addicted04
© 2016 American Society of Plant Biologists
Plant circadian biology has a long history
De Marian (1729) ‘Observation botanique’ of Mimosa pudica: Illustration of ‘sleep’ movements in Medicago, from Charles Darwin (1880) ‘The Power of Movement in Plants’
Figure from Li, J.-D., Burton, K.J., Zhang, C., Hu, S.-B. and Zhou, Q.-Y. (2009). Vasopressin receptor V1a regulates circadian rhythms of locomotor activity and expression of clock-controlled genes in the suprachiasmatic nuclei. Am. J. Physiol. 296: R824-R830, used with permission. Image source: Mylius.
Gene A
Protein B
• The model is out of date (TOC1 actually suppresses CCA1), but provides an example of oscillator structure
From Alabadı́, D., Oyama, T., Yanovsky, M.J., Harmon, F.G., Má s, P. and Kay, S.A. (2001). Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock. Science. 293: 880-883. Reprinted with permission from AAAS
© 2016 American Society of Plant Biologists
darkness
cycles
Circadian clocks control many aspects of human physiology
High alertness 10.00
14.30 Best coordination 15.30 Fastest reaction time Melatonin secretion stops 07.30 17.00 Greatest muscle strength
Gene A
Protein A
Gene B
Protein B
The protein encoded by Gene B represses Gene A
© 2016 American Society of Plant Biologists
The circadian oscillator
Protein A
Environmental Inputs
Circadian gating of entrainment and outputs
Gene
Entrainment pathways Circadian oscillator
Output pathways
Rhythms in: - transcription - physiology - biochemistry
Activation (out of date!) Suppression
Gene B
• It is an oscillator with activation and suppression feedback (compare with previous slide) • The main genes involved are TOC1, LHY and CCA1
An early model for the functioning of Leabharlann Baiduhe circadian clock in Arabidopsis
• This is one of the first structures proposed for the plant circadian clock
Protein A
“sensitive to the Sun and daylight: the leaves & their peduncles fold themselves away & contract around sunset, in the same way they do when the Plant is touched or shaken.”
Synchronize the oscillator with the external time of day so that the clock stays accurate
Output pathways
Circadian gating
Communicate temporal information from the oscillator to other parts of the cell
© 2016 American Society of Plant Biologists
Circadian clocks are biological oscillators with a ~24 hour period
LightDark
Inactive Active
Continuous
- Higher levels of wheel running activity at night - In continuous darkness these rhythms persist but with a ~ 23 hour period
Principles of operation of plant circadian clocks
Aspect of the Circadian System Biological Function
Circadian oscillator
Entrainment pathways
Generate a rhythm with a ~24h period within the cell
© 2016 American Society of Plant Biologists
Reciprocal repression between CCA1 and TOC1 at the core of the circadian clock
Overexpression of CCA1 suppresses circadian oscillations of TOC1 CCA1 and LHY bind to the promoter of TOC1
06.45 Rise in blood pressure
04.30 Lowest body temperature
18.30 Highest blood pressure 19.00 Highest body temperature 21.00 Melatonin secretion starts
02.00 Deepest sleep Deepest sleep
The feedback loop results in rhythms of transcript abundance of the two genes
Gene A
Gene B
Gene A
Protein B
Gene B
0
12
24 36 Time (hours)
Overexpression of TOC1 suppresses circadian oscillations of CCA1
The CCT domain of TOC1 is required for it to bind the CCA1 promoter
From Alabadı́, D., Oyama, T., Yanovsky, M.J., Harmon, F.G., Má s, P. and Kay, S.A. (2001). Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock. Science. 293: 880-883. Reprinted with permission from AAAS. Gendron, J.M., Pruneda-Paz, J.L., Doherty, C.J., Gross, A.M., Kang, S.E. and Kay, S.A. (2012). Arabidopsis circadian clock protein, TOC1, is a DNA-binding transcription factor. Proc. Natl. Acad. Sci. USA 109: 3167-3172. © 2016 American Society of Plant Biologists
Rhythms of Life: The Plant Circadian Clock
Somers, D.E. (1999). The physiology and molecular bases of the plant circadian clock. Plant Physiol. 121: 9-20.
© 2016 American Society of Plant Biologists
Living on a rotating planet is biologically stressful
Over a 24 hour period there is large variation in environmental conditions including temperature, light intensity, humidity and predator behavior
© 2016 American Society of Plant Biologists
The circadian oscillator
Most circadian clocks are transcription-translation feedback loops
The protein encoded by Gene A activates Gene B
Image sources: H. Zell, Charles Darwin “Power of Movement in Plants”
© 2016 American Society of Plant Biologists
Architecture of the circadian clock
© 2016 American Society of Plant Biologists
Adjust the sensitivity of entrainment and output pathways depending on the time of day
© 2016 American Society of Plant Biologists
Interconnected parts of the circadian system
• Extreme day-night temperature difference: 57 oC (-48 oC to 9 oC, Montana, 1972) • Typical day-night fluctuation: ~10 oC each day (central Japan)
See Kudoh, H. (2016). Molecular phenology in plants: in natura systems biology for the comprehensive understanding of seasonal responses under natural environments. New Phytol. 210: 399-412. Image: NASA.
48
• Reciprocal feedback loop • Negative feedback step • Speed of biochemical reactions adds a rate constant
Simple biological oscillator
© 2016 American Society of Plant Biologists
22.30 Bowel movements suppressed
Image source: Addicted04
© 2016 American Society of Plant Biologists
Plant circadian biology has a long history
De Marian (1729) ‘Observation botanique’ of Mimosa pudica: Illustration of ‘sleep’ movements in Medicago, from Charles Darwin (1880) ‘The Power of Movement in Plants’
Figure from Li, J.-D., Burton, K.J., Zhang, C., Hu, S.-B. and Zhou, Q.-Y. (2009). Vasopressin receptor V1a regulates circadian rhythms of locomotor activity and expression of clock-controlled genes in the suprachiasmatic nuclei. Am. J. Physiol. 296: R824-R830, used with permission. Image source: Mylius.
Gene A
Protein B
• The model is out of date (TOC1 actually suppresses CCA1), but provides an example of oscillator structure
From Alabadı́, D., Oyama, T., Yanovsky, M.J., Harmon, F.G., Má s, P. and Kay, S.A. (2001). Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock. Science. 293: 880-883. Reprinted with permission from AAAS
© 2016 American Society of Plant Biologists
darkness
cycles
Circadian clocks control many aspects of human physiology
High alertness 10.00
14.30 Best coordination 15.30 Fastest reaction time Melatonin secretion stops 07.30 17.00 Greatest muscle strength
Gene A
Protein A
Gene B
Protein B
The protein encoded by Gene B represses Gene A
© 2016 American Society of Plant Biologists
The circadian oscillator
Protein A
Environmental Inputs
Circadian gating of entrainment and outputs
Gene
Entrainment pathways Circadian oscillator
Output pathways
Rhythms in: - transcription - physiology - biochemistry
Activation (out of date!) Suppression
Gene B
• It is an oscillator with activation and suppression feedback (compare with previous slide) • The main genes involved are TOC1, LHY and CCA1
An early model for the functioning of Leabharlann Baiduhe circadian clock in Arabidopsis
• This is one of the first structures proposed for the plant circadian clock
Protein A
“sensitive to the Sun and daylight: the leaves & their peduncles fold themselves away & contract around sunset, in the same way they do when the Plant is touched or shaken.”
Synchronize the oscillator with the external time of day so that the clock stays accurate
Output pathways
Circadian gating
Communicate temporal information from the oscillator to other parts of the cell
© 2016 American Society of Plant Biologists
Circadian clocks are biological oscillators with a ~24 hour period
LightDark
Inactive Active
Continuous
- Higher levels of wheel running activity at night - In continuous darkness these rhythms persist but with a ~ 23 hour period
Principles of operation of plant circadian clocks
Aspect of the Circadian System Biological Function
Circadian oscillator
Entrainment pathways
Generate a rhythm with a ~24h period within the cell
© 2016 American Society of Plant Biologists
Reciprocal repression between CCA1 and TOC1 at the core of the circadian clock
Overexpression of CCA1 suppresses circadian oscillations of TOC1 CCA1 and LHY bind to the promoter of TOC1
06.45 Rise in blood pressure
04.30 Lowest body temperature
18.30 Highest blood pressure 19.00 Highest body temperature 21.00 Melatonin secretion starts
02.00 Deepest sleep Deepest sleep