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Arabidopsis COP1 shapes the temporal pattern of CO accumulation conferring a photoperiodic flowering response.

Jang S, Marchal V, Panigrahi KC, Wenkel S, Soppe W, Deng XW, Valverde F, Coupland G - EMBO J. (2008)

Bottom Line: COP1 promotes CO degradation mainly in the dark, so that in cop1 mutants CO protein but not CO mRNA abundance is dramatically increased during the night.However, in the morning CO degradation occurs independently of COP1 by a phytochrome B-dependent mechanism.Thus, COP1 contributes to day length perception by reducing the abundance of CO during the night and thereby delaying flowering under SDs.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany.

ABSTRACT
The transcriptional regulator CONSTANS (CO) promotes flowering of Arabidopsis under long summer days (LDs) but not under short winter days (SDs). Post-translational regulation of CO is crucial for this response by stabilizing the protein at the end of a LD, whereas promoting its degradation throughout the night under LD and SD. We show that mutations in CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a component of a ubiquitin ligase, cause extreme early flowering under SDs, and that this is largely dependent on CO activity. Furthermore, transcription of the CO target gene FT is increased in cop1 mutants and decreased in plants overexpressing COP1 in phloem companion cells. COP1 and CO interact in vivo and in vitro through the C-terminal region of CO. COP1 promotes CO degradation mainly in the dark, so that in cop1 mutants CO protein but not CO mRNA abundance is dramatically increased during the night. However, in the morning CO degradation occurs independently of COP1 by a phytochrome B-dependent mechanism. Thus, COP1 contributes to day length perception by reducing the abundance of CO during the night and thereby delaying flowering under SDs.

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CO protein physically interacts with COP1 in plant cells. (A) Transient co-expression of 35S:YFP:CO and 35S:CFP:COP1 constructs. A 35S:dsRED construct was cotransformed to highlight the transformed cell. The arrows represent the nucleus in which CO and COP1 are colocalized. (B) Enlargement of the nucleus shown in each of the panels represented in (A). (C) Quantification of FRET in vivo between CFP:CO and YFP:COP1. YFP:CO detected as an increase in CFP fluorescence after photobleaching of YFP. Quantification of FRET efficiencies after acceptor photobleaching measured in nuclei and nuclear speckles. Data are mean±s.d. of 10–20 cells from three separate experiments. (D) Visualization of increase in CFP fluorescence after YFP photobleaching. Left-hand panel, cells expressing CFP:COP1 and YFP, which exerts an effect as a negative control. Right-hand panel, cells expressing CFP:COP1 and YFP:CO. Scale bar: 6 μm in (A) and 8 μm in (D).
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f4: CO protein physically interacts with COP1 in plant cells. (A) Transient co-expression of 35S:YFP:CO and 35S:CFP:COP1 constructs. A 35S:dsRED construct was cotransformed to highlight the transformed cell. The arrows represent the nucleus in which CO and COP1 are colocalized. (B) Enlargement of the nucleus shown in each of the panels represented in (A). (C) Quantification of FRET in vivo between CFP:CO and YFP:COP1. YFP:CO detected as an increase in CFP fluorescence after photobleaching of YFP. Quantification of FRET efficiencies after acceptor photobleaching measured in nuclei and nuclear speckles. Data are mean±s.d. of 10–20 cells from three separate experiments. (D) Visualization of increase in CFP fluorescence after YFP photobleaching. Left-hand panel, cells expressing CFP:COP1 and YFP, which exerts an effect as a negative control. Right-hand panel, cells expressing CFP:COP1 and YFP:CO. Scale bar: 6 μm in (A) and 8 μm in (D).

Mentions: Whether the interaction between CO and COP1 also occurred in vivo in plant cells was tested using fluorescent resonance energy transfer (FRET). Microprojectile bombardment was used to co-express cyan fluorescent protein (CFP):COP1 and yellow fluorescent protein (YFP):CO in leaf epidermal cells of Arabidopsis. CFP:COP1 and YFP:CO colocalized to the nucleus and also colocalized in speckles within the nucleus (Figure 4A and B). Physical interaction of CFP:COP1 and YFP:CO was tested by measuring FRET using photoacceptor bleaching, as previously described (Wenkel et al, 2006) (Figure 4C and D). Quantification of FRET signals demonstrated that FRET occurred between YFP:CO and CFP:COP1 both in the nucleus and specifically in nuclear speckles (Figure 4C and D). In control experiments using YFP and CFP, YFP:CO and CFP or YFP and CFP:COP1 FRET was detected at significantly lower levels (Figure 4C). These experiments demonstrate that YFP:CO and CFP:COP1 colocalize and physically interact in the nuclei of plant cells.


Arabidopsis COP1 shapes the temporal pattern of CO accumulation conferring a photoperiodic flowering response.

Jang S, Marchal V, Panigrahi KC, Wenkel S, Soppe W, Deng XW, Valverde F, Coupland G - EMBO J. (2008)

CO protein physically interacts with COP1 in plant cells. (A) Transient co-expression of 35S:YFP:CO and 35S:CFP:COP1 constructs. A 35S:dsRED construct was cotransformed to highlight the transformed cell. The arrows represent the nucleus in which CO and COP1 are colocalized. (B) Enlargement of the nucleus shown in each of the panels represented in (A). (C) Quantification of FRET in vivo between CFP:CO and YFP:COP1. YFP:CO detected as an increase in CFP fluorescence after photobleaching of YFP. Quantification of FRET efficiencies after acceptor photobleaching measured in nuclei and nuclear speckles. Data are mean±s.d. of 10–20 cells from three separate experiments. (D) Visualization of increase in CFP fluorescence after YFP photobleaching. Left-hand panel, cells expressing CFP:COP1 and YFP, which exerts an effect as a negative control. Right-hand panel, cells expressing CFP:COP1 and YFP:CO. Scale bar: 6 μm in (A) and 8 μm in (D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2291449&req=5

f4: CO protein physically interacts with COP1 in plant cells. (A) Transient co-expression of 35S:YFP:CO and 35S:CFP:COP1 constructs. A 35S:dsRED construct was cotransformed to highlight the transformed cell. The arrows represent the nucleus in which CO and COP1 are colocalized. (B) Enlargement of the nucleus shown in each of the panels represented in (A). (C) Quantification of FRET in vivo between CFP:CO and YFP:COP1. YFP:CO detected as an increase in CFP fluorescence after photobleaching of YFP. Quantification of FRET efficiencies after acceptor photobleaching measured in nuclei and nuclear speckles. Data are mean±s.d. of 10–20 cells from three separate experiments. (D) Visualization of increase in CFP fluorescence after YFP photobleaching. Left-hand panel, cells expressing CFP:COP1 and YFP, which exerts an effect as a negative control. Right-hand panel, cells expressing CFP:COP1 and YFP:CO. Scale bar: 6 μm in (A) and 8 μm in (D).
Mentions: Whether the interaction between CO and COP1 also occurred in vivo in plant cells was tested using fluorescent resonance energy transfer (FRET). Microprojectile bombardment was used to co-express cyan fluorescent protein (CFP):COP1 and yellow fluorescent protein (YFP):CO in leaf epidermal cells of Arabidopsis. CFP:COP1 and YFP:CO colocalized to the nucleus and also colocalized in speckles within the nucleus (Figure 4A and B). Physical interaction of CFP:COP1 and YFP:CO was tested by measuring FRET using photoacceptor bleaching, as previously described (Wenkel et al, 2006) (Figure 4C and D). Quantification of FRET signals demonstrated that FRET occurred between YFP:CO and CFP:COP1 both in the nucleus and specifically in nuclear speckles (Figure 4C and D). In control experiments using YFP and CFP, YFP:CO and CFP or YFP and CFP:COP1 FRET was detected at significantly lower levels (Figure 4C). These experiments demonstrate that YFP:CO and CFP:COP1 colocalize and physically interact in the nuclei of plant cells.

Bottom Line: COP1 promotes CO degradation mainly in the dark, so that in cop1 mutants CO protein but not CO mRNA abundance is dramatically increased during the night.However, in the morning CO degradation occurs independently of COP1 by a phytochrome B-dependent mechanism.Thus, COP1 contributes to day length perception by reducing the abundance of CO during the night and thereby delaying flowering under SDs.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany.

ABSTRACT
The transcriptional regulator CONSTANS (CO) promotes flowering of Arabidopsis under long summer days (LDs) but not under short winter days (SDs). Post-translational regulation of CO is crucial for this response by stabilizing the protein at the end of a LD, whereas promoting its degradation throughout the night under LD and SD. We show that mutations in CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a component of a ubiquitin ligase, cause extreme early flowering under SDs, and that this is largely dependent on CO activity. Furthermore, transcription of the CO target gene FT is increased in cop1 mutants and decreased in plants overexpressing COP1 in phloem companion cells. COP1 and CO interact in vivo and in vitro through the C-terminal region of CO. COP1 promotes CO degradation mainly in the dark, so that in cop1 mutants CO protein but not CO mRNA abundance is dramatically increased during the night. However, in the morning CO degradation occurs independently of COP1 by a phytochrome B-dependent mechanism. Thus, COP1 contributes to day length perception by reducing the abundance of CO during the night and thereby delaying flowering under SDs.

Show MeSH
Related in: MedlinePlus