第十章 第二讲 植物开花时间控制的分子机理
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第十章 基因和发育 第二讲
植物开花时间控制的分子机理
Molecular mechanism of plant flowering time control
By Hongwei Guo, Peking University, 2008.12.18
Transition to reproduction
When to flower is a matter of the survival
Photoperiodic flowering
Two essential questions: 1. How does the leaf measure day-length? 2. What is the florigen?
Genetics provides the answers
Arabidopsis: Long Day Plant Flowering is induced by Long Day (LD)
of species
Vegetative phase
Reproductive phase
Two major pathways regulating floral transition
Photoperiodic flowering (光周期开花): daylength dependent flowering time control Vernalization (春化): cold-promoted flowering
• the flowering signal is generated
SAM
in the leaf
• the signal goes one way: from the leaf to the apex
• Grafting transmittable
Florigen
Florigen Florigen
SD: late flowering
phyBDE: early flowering cry2: late flowering
Cry inhibits CO protein degradation in light
When CO mRNA peaks at midnight in SDs, COP1 is predominantly localized in the nucleus. CRY interacts with COP1 but is not able to repress its activity. COP1–CO interaction results in ubiquitination and degradation of CO (A), whereas when CO mRNA peaks in the afternoon in LDs, light activation of CRY during the daytime might mediate translocation of COP1 from nucleus to cytoplasm. Consequently, CO is able to accumulate and activate the transcription of FT to promote floweቤተ መጻሕፍቲ ባይዱing (B). U, ubiquitin.
(“Maryland Mammoth” cultivar of tobacco)
Floral induction of leaves of Short Day plant Perrila crispa
“Something” must be produced in leaves and “move” to the meristem Long journey to identify “Florigen” began
PRR: photoperiod response regulator
PRR: photoperiod response regulator
CO is essential for photoperiodic flowering, as co mutant is late flowering and almost a day-neutral plant. It encodes a transcriptional regulator.
Certain late flowering mutants are blind to photoperiod
cryptochrome 2 (cry2) phytochrome A (phyA) contstans (co) flowering locus t (ft)
Cry2: blue light receptor PhyA: Far-red light receptor CO: transcriptional co-activator FT: transcriptional co-activator (?)
Is co the PRR（春th化a）t measures daylength?
LFY A, B, C, E class genes
CO is required for FT expression
FT mRNA levels determine flowering time
LD: early flowering
phyA also absorbs blue light
Signal Transduction
(originally proposed by Boenning, 1936)
Light has a dual role in this model: - entrains the circadian oscillation of light- and dark-sensitive phases
(Lang and Zeevart)
Multiple grafting experiment with Perilla
Long distance transport---- thru vascular tissue
The flowering signal: florigen
vegetative or reproductive growth?
3 wavelengths (Blue, Red, Far-red) are important in regulating plant growth and development
Phytochromes (光敏色素）：Red/Far-red light receptors Cryptochromes (隐花色素）：Blue light receptors
植物开花时间控制的分子机理
Molecular mechanism of plant flowering time control
By Hongwei Guo, Peking University, 2008.12.18
Transition to reproduction
When to flower is a matter of the survival
Photoperiodic flowering
Two essential questions: 1. How does the leaf measure day-length? 2. What is the florigen?
Genetics provides the answers
Arabidopsis: Long Day Plant Flowering is induced by Long Day (LD)
of species
Vegetative phase
Reproductive phase
Two major pathways regulating floral transition
Photoperiodic flowering (光周期开花): daylength dependent flowering time control Vernalization (春化): cold-promoted flowering
• the flowering signal is generated
SAM
in the leaf
• the signal goes one way: from the leaf to the apex
• Grafting transmittable
Florigen
Florigen Florigen
SD: late flowering
phyBDE: early flowering cry2: late flowering
Cry inhibits CO protein degradation in light
When CO mRNA peaks at midnight in SDs, COP1 is predominantly localized in the nucleus. CRY interacts with COP1 but is not able to repress its activity. COP1–CO interaction results in ubiquitination and degradation of CO (A), whereas when CO mRNA peaks in the afternoon in LDs, light activation of CRY during the daytime might mediate translocation of COP1 from nucleus to cytoplasm. Consequently, CO is able to accumulate and activate the transcription of FT to promote floweቤተ መጻሕፍቲ ባይዱing (B). U, ubiquitin.
(“Maryland Mammoth” cultivar of tobacco)
Floral induction of leaves of Short Day plant Perrila crispa
“Something” must be produced in leaves and “move” to the meristem Long journey to identify “Florigen” began
PRR: photoperiod response regulator
PRR: photoperiod response regulator
CO is essential for photoperiodic flowering, as co mutant is late flowering and almost a day-neutral plant. It encodes a transcriptional regulator.
Certain late flowering mutants are blind to photoperiod
cryptochrome 2 (cry2) phytochrome A (phyA) contstans (co) flowering locus t (ft)
Cry2: blue light receptor PhyA: Far-red light receptor CO: transcriptional co-activator FT: transcriptional co-activator (?)
Is co the PRR（春th化a）t measures daylength?
LFY A, B, C, E class genes
CO is required for FT expression
FT mRNA levels determine flowering time
LD: early flowering
phyA also absorbs blue light
Signal Transduction
(originally proposed by Boenning, 1936)
Light has a dual role in this model: - entrains the circadian oscillation of light- and dark-sensitive phases
(Lang and Zeevart)
Multiple grafting experiment with Perilla
Long distance transport---- thru vascular tissue
The flowering signal: florigen
vegetative or reproductive growth?
3 wavelengths (Blue, Red, Far-red) are important in regulating plant growth and development
Phytochromes (光敏色素）：Red/Far-red light receptors Cryptochromes (隐花色素）：Blue light receptors