Distinct regulation of CAB and PHYB gene expression by similar circadian clocks.
Phytochrome B (phyB) is a major phytochrome active in light-grown plants. The circadian clock controls the expression of the PHYB gene. We have used the luciferase reporter gene (LUC) to monitor the rhythmic expression of PHYB in photoreceptor and clock-associated mutant backgrounds. Surprisingly, we found that PHYB and CAB expression have different free-running periods, indicating that separate circadian clocks control these genes. The effects of mutations show that the clocks share common components. This suggests that they are copies of the same clock mechanism in different locations, most likely in different cell layers. Furthermore, we show that phyB is required for a negative feedback loop that strongly antagonises the expression of PHYB. Compared to a system with only one clock, this regulatory complexity might allow the phase of peak expression for one clock-controlled gene to alter, relative to other genes or to changing environmental conditions.
Hall
Anthony
A
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
Kozma-Bognár
László
L
Bastow
Ruth M
RM
Nagy
Ferenc
F
Millar
Andrew J
AJ
D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics*; D002940:Circadian Rhythm; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D017930:Genes, Reporter; D008156:Luciferases; D009154:Mutation; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics*; D051939:Phytochrome B; D014157:Transcription Factors
D029681:Arabidopsis Proteins; C497952:PHYB protein, Arabidopsis; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B; D008156:Luciferases