Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis

Ponnu, Jathish; Hoecker, Ute

doi:10.3389/fpls.2021.662793

Cited by 69 publications

(56 citation statements)

References 227 publications

(309 reference statements)

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“…The ER stress-sensitive phenotype of cop1-4 was fully rescued by complementation with constructs expressing COP1 and COP1 L105A but not by those expressing COP1 L170A and COP1 MUT ( Figure 3 , Figures S3 and S4 ). These results are consistent with those of previous studies, which showed that the nuclear localization of COP1 is important for regulation of its target proteins, which is needed to suppress photomorphogenesis [ 25 , 32 , 40 , 41 ]. Despite the nuclear localization of the COP1 L170A , complementation of the cop1-4 mutant with COP1 L170A failed to rescue its ER stress-sensitive phenotype and to normalize its photomorphogenic response ( Figure 3 , Figures S3 and S4 ).…”

Section: Discussionsupporting

confidence: 93%

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

Kang

Lee

Nawkar

et al. 2021

IJMS

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Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.

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Section: Discussionsupporting

confidence: 93%

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

Kang

Lee

Nawkar

et al. 2021

IJMS

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“…The CCT domains of CRY1 and CRY2 interact with COP1 ( Wang et al, 2001 ; Yang et al, 2001 ; Ponnu et al, 2019 ), an E3 ubiquitin ligase that inhibits light signaling by polyubiquitinating multiple transcription factors acting in the various light responses. COP1 is mainly active in darkness, thereby preventing an accumulation of these substrate transcription factors which leads to a suppression of light responses in darkness ( Huang et al, 2014 ; Hoecker, 2017 ; Ponnu and Hoecker, 2021 ). Epistatic analyses of cop1 and cry1 mutants suggested early on that CRYs initiate light signaling in blue light by inhibiting the activity of COP1 ( Ang and Deng, 1994 ; Figures 1 , 2 ).…”

Section: Signal Transduction Through Cryptochrome-interacting Proteinsmentioning

confidence: 99%

Signaling Mechanisms by Arabidopsis Cryptochromes

Ponnu

Hoecker

2022

Front. Plant Sci.

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Cryptochromes (CRYs) are blue light photoreceptors that regulate growth, development, and metabolism in plants. In Arabidopsis thaliana (Arabidopsis), CRY1 and CRY2 possess partially redundant and overlapping functions. Upon exposure to blue light, the monomeric inactive CRYs undergo phosphorylation and oligomerization, which are crucial to CRY function. Both the N- and C-terminal domains of CRYs participate in light-induced interaction with multiple signaling proteins. These include the COP1/SPA E3 ubiquitin ligase, several transcription factors, hormone signaling intermediates and proteins involved in chromatin-remodeling and RNA N6 adenosine methylation. In this review, we discuss the mechanisms of Arabidopsis CRY signaling in photomorphogenesis and the recent breakthroughs in Arabidopsis CRY research.

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“…After phytochrome or cryptochrome activation by light, these photoreceptors inhibit the COP1/SPA activity, causing stabilization of the targeted transcription factors and subsequent light response. More than two dozens of transcription factors have so far been identified as COP1/SPA targets, including HYPOCOTYL5 (HY5), CONSTANS and PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1)/PAP2, and many of them share a conserved COP1‐binding motif consisting of a valine–proline (VP) sequence (Ponnu & Hoecker, 2021).…”

Section: Introductionmentioning

confidence: 99%

Functional comparison of the WD‐repeat domains of SPA1 and COP1 in suppression of photomorphogenesis

Kerner

Nagano

Lübbe

et al. 2021

Plant Cell & Environment

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The Arabidopsis COP1/SPA complex acts as a cullin4‐based E3 ubiquitin ligase to suppress photomorphogenesis in darkness. It is a tetrameric complex of two COP1 and two SPA proteins. Both COP1 and SPA are essential for the activity of this complex, and they both contain a C‐terminal WD‐repeat domain responsible for substrate recruitment and binding of DDB1. Here, we used a WD domain swap‐approach to address the cooperativity of COP1 and SPA proteins. We found that expression of a chimeric COP1 carrying the WD‐repeat domain of SPA1 mostly complemented the cop1‐4‐mutant phenotype in darkness, indicating that the WD repeat of SPA1 can replace the WD repeat of COP1. In the light, SPA1‐WD partially substituted for COP1‐WD. In contrast, expression of a chimeric SPA1 protein carrying the WD repeat of COP1 did not rescue the spa‐mutant phenotype. Together, our findings demonstrate that a SPA1‐type WD repeat is essential for COP1/SPA activity, while a COP1‐type WD is in part dispensible. Moreover, a complex with four SPA1‐WDs is more active than a complex with only two SPA1‐WDs. A homology model of SPA1‐WD based on the crystal structure of COP1‐WD uncovered two insertions and several amino acid substitutions at the predicted substrate‐binding pocket of SPA1‐WD.

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Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis

Cited by 69 publications

References 227 publications

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

Signaling Mechanisms by Arabidopsis Cryptochromes

Functional comparison of the WD‐repeat domains of SPA1 and COP1 in suppression of photomorphogenesis

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