Light signal provides the spatial and temporal information for plants to adapt to the prevailing environmental conditions. Alterations in light quality and quantity can trigger robust changes in global gene expression. In
CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) is a highly conserved E3 ubiquitin ligase from plants to animals and acts as a central repressor of photomorphogenesis in plants. SUPPRESSOR OF PHYA-105 1 family members (SPA1-SPA4) directly interact with COP1 and enhance COP1 activity. Despite the presence of a kinase domain at the N-terminus, no COP1-independent role of SPA proteins has been reported. Here we show that SPA1 acts as a serine/threonine kinase and directly phosphorylates PIF1 in vitro and in vivo. SPAs are necessary for the light-induced phosphorylation, ubiquitination and subsequent degradation of PIF1. Moreover, the red/far-red light photoreceptor phyB interacts with SPA1 through its C-terminus and enhances the recruitment of PIF1 for phosphorylation. These data provide a mechanistic view on how the COP1-SPA complexes serve as an example of a cognate kinase-E3 ligase complex that selectively triggers rapid phosphorylation and removal of its substrates, and how phyB modulates this process to promote photomorphogenesis.
more » « less- NSF-PAR ID:
- 10154034
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary Arabidopsis thaliana , two groups of key factors regulating those changes in gene expression areCONSTITUTIVE PHOTOMORPHOGENESIS /DEETIOLATED /FUSCA (COP /DET /FUS ) and a subset of basic helix‐loop‐helix transcription factors calledPHYTOCHROME ‐INTERACTING FACTORS (PIF s). Recently, rapid progress has been made in characterizing the E3 ubiquitin ligases for the light‐induced degradation ofPIF 1,PIF 3 andPIF 4; however, the E3 ligase(s) forPIF 5 remains unknown. Here, we show that theCUL 4COP 1–SPA complex is necessary for the red light‐induced degradation ofPIF 5. Furthermore,COP 1 andSPA proteins stabilizePIF 5 in the dark, but promote the ubiquitination and degradation ofPIF 5 in response to red light through the 26S proteasome pathway. Genetic analysis illustrates that overexpression ofPIF 5cop1‐4 andspaQ seedling de‐etiolation phenotypes under dark and red‐light conditions. In addition, thePIF 5 protein level cycles under both diurnal and constant light conditions, which is also defective in thecop1‐4 andspaQ backgrounds. Bothcop1‐4 andspaQ show defects in diurnal growth pattern. Overexpression ofPIF 5cop1‐4 andspaQ under diurnal conditions, suggesting that theCOP 1–SPA complex plays an essential role in photoperiodic hypocotyl growth, partly through regulating thePIF 5 level. Taken together, our data illustrate how theCUL 4COP 1–SPA E3 ligase dynamically controls thePIF 5 level to regulate plant development. -
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Photomorphogenesis is repressed in the dark mainly by an E3 ubiquitin ligase complex comprising CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and four homologous proteins called SUPPRESSOR OF PHYA‐105 (SPA1–SPA4) in Arabidopsis. This complex induces the ubiquitination and subsequent degradation of positively acting transcription factors (TFs; e.g. ELONGATED HYPOCOTYL (HY5), LONG HYPOCOTYL IN FAR‐RED 1 (HFR1), PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) and others] in the dark to repress photomorphogenesis. Genomic evidence showed a large number of genes regulated by COP1 in the dark, of which many are direct targets of HY5. However, the genomic basis for the constitute photomorphogenic phenotype of
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