Photoperiodism Flashcards
1
Q
How does daylength independent circadian rhythm occur in plants?
A
- Degredation of miRNA 156 RNA hairpin
- Leads to cleavage of target genes
- Targets include SPLs which regulate flower promoting genes
- miRNA 156 represses flowering in juvenile stage, but decreases with sugar levels
2
Q
What is the coincidence detector between the plant circadian and daylight timers, what does it regulate?
A
- Constants (CO)
- regulates abundance of CDF1 which represses transcription of growth factors
3
Q
How is CO regulated by the circadian rhythm?
A
- crypto and photochrome react with light causing them to migrate to the nucleus
- Promoting transcription of CCA1
- But CCA1 if repressed by TOC1 which is degraded by daylight
- CCA1 inhibits FKF1
- FKF1 inhibits CDF1, allowing CO transcription
4
Q
How is CO regulated by the daylight cycle?
A
- phyto and cytochromes migrate to nucleus
- CRY and the chromes inhibit COP1, preventing CO degradation
5
Q
How is CO regulated by the circadian rhythm?
A
- PR turns to PFR and migrates to nucleus
- Light also alters CRY which regulates COP1 for export
- Prevents COP1 from degrading CO, TF for FT
6
Q
How do the daytime and circadian systems coincide on CO?
A
- Circadian limits transcription
- Daylight degrades in absence of long enough light
- CO promotes FT
