The COP1-ADA2b module mediates light regulation of DNA double-strand break repair in Arabidopsis

Chen, Li; Diao, Liman; Ruan, Jiaqi; Deng, Yanli; Zhang, Kai; Guan, Yan; Li, Ling; Liang, Min; Peng, Lina; Shi, Jiayi; Zhang, Shilong; Liu, Minqing; Li, Yupeng; Mao, Zhilei; Wang, Wenxiu; Yang, Hong-Quan; Guo, Tongtong

doi:10.1038/s41467-026-70673-z

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Published: 13 March 2026

The COP1-ADA2b module mediates light regulation of DNA double-strand break repair in Arabidopsis

Li Chen¹^na1,
Liman Diao¹^na1,
Jiaqi Ruan¹,
Yanli Deng¹,
Kai Zhang¹,
Yan Guan¹,
Ling Li²,
Min Liang¹,
Lina Peng¹,
Jiayi Shi¹,
Shilong Zhang¹,
Minqing Liu¹,
Yupeng Li¹,
Zhilei Mao¹,
Wenxiu Wang¹,
Hong-Quan Yang ORCID: orcid.org/0000-0001-6215-2665¹ &
…
Tongtong Guo ORCID: orcid.org/0000-0003-0462-3929¹

Nature Communications volume 17, Article number: 3876 (2026) Cite this article

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Abstract

DNA double-strand break (DSB) represents the most severe form of DNA damage, and both defective and hyperactive repair can compromise genome stability. It is known that blue light promotes DSB repair by cryptochromes (CRYs)-enhanced STRUCTURAL MAINTENANCE OF CHROMOSOME 5/6 (SMC5/6) complex recruitment via ALTERATION/DEFICIENCY IN ACTIVATION 2B (ADA2b). Here, we report a negative regulatory module consisting of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), an E3 ubiquitin ligase acting as a central repressor of photomorphogenesis, and ADA2b, a pivotal positive regulator of DNA repair, mediates light regulation of DSB repair. Light induces the accumulation of ADA2b, while COP1 physically interacts with ADA2b to mediate its ubiquitination and degradation through the 26S proteasome. The cop1-4 mutant exhibits enhanced DNA damage resistance under various light conditions, whereas the red/far-red photoreceptor phytochrome A and B (phyA/phyB) mutant displays hypersensitivity under red light. COP1 lies upstream of ADA2b but downstream of CRYs and phyB to regulate DNA repair. These findings reveal a pivotal role for the COP1-ADA2b module in CRYs- and phyA/phyB-mediated light regulation of DSB repair. The antagonistic regulation of ADA2b stability by photoreceptors and COP1 may dynamically calibrate DNA repair activity to maintain genome stability and optimize plant growth according to the fluctuating light conditions.

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Introduction

Light is a crucial environmental signal that regulates various physiological processes essential for plant growth and development. To perceive and respond to light, plants utilize a diverse set of photoreceptors, such as blue light receptors cryptochromes and red/far-red light receptors phytochromes^1,2,3. Arabidopsis has two cryptochromes, CRY1 and CRY2, which primarily regulate photomorphogenesis and photoperiodic flowering, respectively^1,2. Arabidopsis possesses five phytochromes (phyA to phyE), with phyA functioning as the far-red light receptor and phyB serving as the primary receptor for red light to promote photomorphogenesis^4,5. Phytochromes convert between biologically inactive Pr and active Pfr forms in response to far-red and red light, respectively³. CRYs and PHYs co-regulate essential processes including photomorphogenesis, circadian rhythms, shade avoidance, and stomatal development^6,7,8,9,10.

COP1 is a key negative regulator of photomorphogenesis that functions as an E3 ubiquitin ligase to control the stability of downstream factors involved in light-regulated processes^11,12. COP1 comprises an N-terminal RING-finger domain, a central coiled-coil domain, and C-terminal WD40 repeats¹¹. Photoreceptors inhibit COP1 function by modulating its nuclear translocation, interfering with COP1-SUPPRESSOR OF PHYA-105 (SPA) complex formation, and competing with its substrates to prevent COP1-mediated degradation of light-regulated factors^{13,14,15,16,17,18,19,20,21,22}. COP1 mediates the degradation of numerous positive key regulators of light signaling through the 26S proteasome pathway, such as ELONGATED HYPOCOTYL 5 (HY5), LONG AFTER FAR-RED LIGHT 1 (LAF1), B-box proteins (BBXs), LONG HYPOCOTYL IN FAR-RED 1 (HFR1), CONSTANS (CO), and SCREAMs (SCRMs), to negatively regulate photomorphogenesis, shade avoidance, photoperiodic flowering, and stomatal development^{23,24,25,26,27,28,29,30}. Thus, light signaling controls various growth and developmental processes through the regulation of specific COP1-substrate modules.

Organisms are constantly exposed to DNA damage, which poses a significant threat to genomic stability. DSBs are the most severe, directly causing chromosomal breakage. DSBs are primarily repaired through non-homologous end joining (NHEJ) or homologous recombination (HR)³¹. Although HR is comparatively error-free, excessive non-allelic HRs within repetitive sequences can result in large-scale deletions or expansions³². In Arabidopsis, HR requires the recruitment of the SMC5/6 complex to the DSBs, a process mediated by ADA2b^33,34. ADA2b contains a zinc-finger domain and a SWI3, ADA2, N-CoR, and TFIIIB (SANT) domain at its N terminus and a Swi3p, Rsc8p, and Moira (SWIRM) domain at the C terminus, and functions as part of the Spt-Ada-Gcn5 acetyltransferase (SAGA) complex to enhance GENERAL CONTROL NON DEREPRESSIBLE 5 (GCN5) acetyltransferase activity³⁵. Studies have shown that ada2b mutant exhibits severe defects in DNA repair^33,36. Upon DNA damage, DSBs trigger the production of diRNAs, which sequentially recruit ARGONAUTE 2 (AGO2), INVOLVED IN DE NOVO 2 (IDN2), CELL DIVISION CYCLE 5 (CDC5), and ADA2b, ultimately facilitating the recruitment of the SMC5/6 complex to DSBs for subsequent repair^33,34,37.

Although light is a key environmental factor governing diverse plant growth processes, its role in regulating DNA repair has only recently received attention. It has been demonstrated that CRYs act as positive regulators to mediate blue light-induced DNA repair by promoting ADA2b-dependent recruitment of the SMC5/6 complex and enhancing the expression of DNA repair-related genes^36,38,39. However, whether DNA repair is negatively regulated by components in the light signaling pathway remains unknown. Here, we show that light signals induce ADA2b accumulation, while COP1 physically interacts with ADA2b to mediate its ubiquitination and degradation. cop1-4 mutant exhibits enhanced resistance to DNA damage under various light conditions, whereas the phyA phyB double mutant displays increased sensitivity to DNA damage under red light. COP1 acts upstream of ADA2b, but downstream of CRYs and phyB to regulate DNA repair. These findings underscore the pivotal role of COP1 in modulating DNA repair by controlling ADA2b stability in response to light. We propose that the antagonistic regulation of ADA2b by COP1 and the photoreceptors CRYs and phyB prevents insufficient correction or excessive genomic rearrangements, thereby precisely optimizing the DNA repair status according to the ambient light conditions to ensure genome stability.

Results

Blue and red/far-red light induce ADA2b accumulation

During our previous investigation into the role of blue light receptor CRYs in mediating DSB repair via ADA2b³⁶, we noticed that blue light markedly enhanced ADA2b accumulation compared to darkness (Fig. 1a–c, Supplementary Fig. 1). Moreover, white, red, and far-red light also promoted ADA2b accumulation (Fig. 1a–c, Supplementary Fig. 1). We generated transgenic plants overexpressing ADA2b fused to YFP (YFP-ADA2b-OX) in phyA phyB mutant background (YFP-ADA2b-OX/phyA phyB), and, used this and YFP-ADA2b-OX/cry1 cry2³⁶ lines of plants to analyze ADA2b accumulation in WT and phyA phyB backgrounds under red and far-red light, and WT and cry1 cry2 backgrounds under blue light, respectively. The results showed that blue and red/far-red light-induced accumulation of ADA2b was significantly reduced in YFP-ADA2b-OX/cry1 cry2 and YFP-ADA2b-OX/phyA phyB seedlings, respectively (Fig. 1d, e), indicating that CRYs and phyA/phyB mediate blue and red/far-red light, respectively, to promote ADA2b accumulation.

**Fig. 1: Light induces ADA2b protein accumulation.**

COP1 interacts with ADA2b to mediate its ubiquitination

To determine whether light-dependent regulation of ADA2b stability is mediated by E3 ubiquitin ligase COP1, the central negative regulator of light signaling, we first examined the interaction between COP1 and ADA2b. We performed yeast two-hybrid assays using COP1 (and its truncations) as bait and ADA2b (and its truncations) as prey. The results indicate that COP1 interacts with ADA2b in yeast, with its N-terminal region (N282) and the C-terminal region of ADA2b (ADA2bC) being critical for this interaction (Fig. 2a, Supplementary Fig. 2, and Supplementary Fig. 3). To further confirm the direct interaction, we carried out pull-down assays using GST-ADA2b (or GST as control) as bait and His-TF-COP1 (or His-TF as control) as prey. His-TF-COP1, but not His-TF, was pulled down by GST-ADA2b, whereas GST failed to pull down His-TF-COP1 (Fig. 2b). These findings demonstrate that COP1 directly interacts with ADA2b in vitro.

To investigate whether this interaction occurs in planta, we first performed luciferase complementation assays by co-expressing full-length ADA2b or its truncations fused to the N-terminal fragment of luciferase (nLUC) with COP1 fused to the C-terminal fragment (cLUC). The results showed that co-expression of nLUC fused to the full-length ADA2b (ADA2b-nLUC) or its C-terminal fragment (ADA2bC-nLUC), but not its N-terminal fragment (ADA2bN-nLUC), with cLUC-COP1 reconstituted luciferase activity (Fig. 2c). Consistently, protein co-localization assays showed that COP1-mCherry was co-localized with YFP-ADA2b in the several nuclear bodies, and co-localized with YFP-ADA2bC in one single large nuclear body, while not co-localized with YFP-ADA2bN (Fig. 2d). These results indicate that the C-terminal region of ADA2b mediates its interaction with COP1 in tobacco cells. To further confirm that ADA2b and COP1 indeed physically interact within these nuclear bodies, we performed bimolecular fluorescence complementation (BiFC) assays by coexpressing COP1 fused to the C-terminal half of YFP (COP1-cYFP) and ADA2b fused to the N-terminal half of YFP (nYFP-ADA2b) in tobacco cells. As shown in Supplementary Fig. 4, YFP fluorescence signals were clearly observed forming nuclear bodies in the nuclei of cells coexpressing nYFP-ADA2b and COP1-cYFP in white light and in the dark, while no signals were detected in the nuclei of cells coexpressing nYFP-ADA2b and cYFP, or nYFP and COP1-cYFP. These results again suggest that COP1 interacts with ADA2b in tobacco cells.

To further validate this interaction in Arabidopsis, we first performed immunofluorescence co-localization assays. Upon application of DNA damage agent methyl methanesulfonate (MMS), YFP-ADA2b was partially co-localized with endogenous COP1 at the DSB foci (marked by γH2AX) in the nuclei of YFP-ADA2b-OX seedlings in white light, indicating the spatiotemporal possibilities of interaction between COP1 and ADA2b in Arabidopsis cells (Fig. 2e). Then we generated double transgenic lines co-overexpressing YFP-ADA2b and GUS-COP1 (YFP-ADA2b-OX/GUS-COP1-OX) via genetic crossing, followed by co-immunoprecipitation (co-IP) assays. As shown in Supplementary Fig. 5, IP of YFP-ADA2b co-precipitated GUS-COP1 in the extracts from dark-adapted YFP-ADA2b-OX/GUS-COP1-OX seedlings, but not in those from GUS-COP1-OX seedlings. We also tested the association of YFP-ADA2b with the endogenous COP1 through co-IP assays with dark-adapted or white light-irradiated YFP-ADA2b-OX seedlings pretreated with MG132 and MMS. The result showed that IP of YFP-ADA2b co-precipitated with much more endogenous COP1 in extracts from dark-adapted YFP-ADA2b-OX seedlings than those in extracts from white light-irradiated YFP-ADA2b-OX seedlings, but no endogenous COP1 was co-precipitated in extracts from seedlings expressing YFP only (Fig. 2f). These results demonstrate that COP1 interacts with ADA2b in vivo, and light can repress this interaction.

To determine whether COP1 mediates the ubiquitination of ADA2b through their interaction, we performed in vitro ubiquitination assays. We expressed and purified the GST-ADA2b protein in E. coli as a substrate and MBP-COP1 protein as the E3 ligase, with MBP as control. The result showed that, in the presence of E1, E2, and Flag-tagged ubiquitin, GST-ADA2b was ubiquitinated by MBP-COP1, but not MBP (Supplementary Fig. 6). We then performed in vivo ubiquitination assays by immunoprecipitating YFP-ADA2b and detecting its ubiquitination using dark-adapted or white light-irradiated YFP-ADA2b-OX seedlings pretreated with MG132 and MMS, and YFP seedlings as control. The result showed that more YFP-ADA2b proteins were ubiquitinated in extracts from dark-adapted YFP-ADA2b-OX seedlings than those in extracts from YFP-ADA2b-OX seedlings irradiated by white light, but the ubiquitination can barely be detected in extracts from seedlings expressing YFP only (Supplementary Fig. 7). The result demonstrates that ADA2b can be specifically ubiquitinated in vivo, and light can inhibit this ubiquitination. To determine whether this in vivo ubiquitination of ADA2b is mediated by COP1, we generated YFP-ADA2b overexpression plants in the cop1-4 mutant background (YFP-ADA2b-OX/cop1-4) via genetic crossing. We determined the ubiquitination of YFP-ADA2b in WT and cop1-4 mutant backgrounds by immunoprecipitating YFP-ADA2b and detecting its ubiquitination using dark-adapted and MG132-treated YFP-ADA2b-OX and YFP-ADA2b-OX/cop1-4 seedlings. The results showed that the level of ubiquitinated YFP-ADA2b was strikingly lower in cop1-4 mutant than in WT background (Fig. 2g), indicating that COP1 mediates the ubiquitination of ADA2b.

COP1 mediates the degradation of ADA2b via the 26S proteasome pathway

To determine whether ADA2b degradation occurs through the 26S proteasome pathway, we performed cell-free degradation assays. YFP-ADA2b was largely degraded within 2 h without the proteasome inhibitors MG132 and MG115, while application of these inhibitors clearly inhibited YFP-ADA2b degradation (Fig. 3a, b). We further examined YFP-ADA2b degradation in YFP-ADA2b-OX seedlings transferred from white light to darkness with or without proteasome inhibitors MG132 or Bortezomib (BTZ). The results showed that dark-induced degradation of YFP-ADA2b was markedly suppressed by these proteasome inhibitors (Fig. 3c–e, Supplementary Fig. 8). These data suggest that ADA2b undergoes the 26S proteasome pathway-dependent degradation in darkness.

**Fig. 3: COP1 mediates ADA2b degradation via the 26S proteasome pathway.**

Furthermore, we examined YFP-ADA2b accumulation using YFP-ADA2b-OX and YFP-ADA2b-OX/cop1-4 seedlings grown in white, blue, or red light, which were treated with the de novo protein synthesis inhibitor cycloheximide (CHX) to block new YFP-ADA2b protein synthesis, with or without MG132, and then transferred into darkness. The results showed that, in the presence of COP1, dark-induced degradation of YFP-ADA2b was inhibited by MG132, and in the absence of COP1, the degradation of YFP-ADA2b was suppressed in darkness even without MG132 (Fig. 3f, and Supplementary Fig. 9). These results demonstrate that COP1 mediates the degradation of ADA2b through the 26S proteasome pathway in the dark.

Disruption of COP1 leads to enhanced DNA damage resistance

Given that COP1 directly interacts with ADA2b to mediate its degradation, and ADA2b is essential for DNA repair³³, we hypothesized that COP1 might also participate in DNA repair. Compared to WT plants, the cop1-4 mutant exhibited longer roots and a significantly increased number of root meristematic cells in the dark or dim white light, suggesting that cop1-4 mutant might accumulate less DNA damage that induces cell cycle arrest (Fig. 4a, b, Supplementary Fig. 10). Comet assays further revealed that cop1-4 etiolated seedlings displayed reduced DNA damage accumulation compared with WT, implying that COP1 might play a negative role in DNA damage repair during plant growth and development in the dark (Fig. 4c).

**Fig. 4: Disruption of COP1 leads to decreased DNA damage accumulation.**

To further investigate the role of COP1 in DNA damage response, we tested the sensitivity of the cop1-4 mutant to various DNA damage treatments. We observed that cop1-4 mutant maintained significantly higher relative fresh weights after treatments with UV-C or DNA damage agents (MMS, bleomycin (BLM), Camptothecin (CPT), and Zeocin) under white, blue, and red light, respectively, suggesting that cop1-4 mutant may exhibit enhanced DNA damage resistance (Fig. 4d–f, Supplementary Fig. 11, and Supplementary Fig. 12). Specifically, after treatment with 6 kJ/m² UV-C, the cop1-4 mutant developed significantly fewer pale cotyledons than WT in white, blue, and red light, respectively, indicating a higher survival rate after UV-C irradiation (Fig. 4d, e, g, Supplementary Fig. 11, and Supplementary Fig. 12). Furthermore, immunofluorescence assays showed fewer γ-H2AX foci (a DSB marker) and comet assays revealed less DNA in tail in cop1-4 nuclei after MMS treatment in dim white light, suggesting reduced DNA damage accumulation (Fig. 4h, i, Supplementary Fig. 13). These results collectively indicate that COP1 may negatively regulate DNA repair.

COP1 regulates DNA repair via ADA2b degradation

To investigate whether COP1 regulates DNA repair through degrading ADA2b, we compared the accumulation of YFP-ADA2b in YFP-ADA2b-OX and YFP-ADA2b-OX/cop1-4 seedlings grown under constant darkness or high-intensity white light. We found that considerably more YFP-ADA2b accumulated in YFP-ADA2b-OX/cop1-4 seedlings than in YFP-ADA2b-OX seedlings in the dark, whereas COP1 mutation led to only a modest increase in YFP-ADA2b accumulation in high-intensity white light (Fig. 5a–c, Supplementary Fig. 14).

Fig. 5: COP1 mutation-caused ADA2b accumulation leads to increased DNA damage resistance. — **Fig. 5: *COP1* mutation-caused ADA2b accumulation leads to increased DNA damage resistance.**

Consistent with the higher YFP-ADA2b protein levels, YFP-ADA2b-OX/cop1-4 seedlings exhibited longer roots and an increased number of root meristematic cells than YFP-ADA2b-OX seedlings in darkness, while no significant difference was observed in root length and meristematic cell number under high-intensity white light (Fig. 5d, e, Supplementary Fig. 15). Furthermore, under dim white light, an intermediate condition expected to preserve comparatively greater COP1 activity than the high-intensity white light used above, MMS-treated YFP-ADA2b-OX/cop1-4 seedlings showed fewer γ-H2AX foci in immunofluorescence assays and less DNA in tail in comet assays than YFP-ADA2b-OX seedlings, suggesting enhanced resistance to DNA damage (Fig. 5f, g). Taken together, these results indicate that COP1 negatively regulates DNA repair, likely by modulating the light-dependent stabilization of ADA2b.

COP1-mediated ADA2b degradation impairs the recruitment of SMC5 to DSBs

Given that COP1 regulates DNA repair by modulating ADA2b stability, we next asked whether this regulation specifically impairs the function of ADA2b to recruit SMC5 to DSBs. To test this, we generated transgenic lines overexpressing SMC5-YFP fusion protein in cop1-4 and cop1-4 ada2b mutant backgrounds (SMC5-YFP-OX/cop1-4 and SMC5-YFP-OX/cop1-4 ada2b) by genetic crossing. We have previously shown that ADA2b-mediated recruitment of SMC5 is largely dependent on CRYs and blue light³⁶. Consistently, here we observed that SMC5-YFP largely failed to form discrete foci and remained diffusely distributed in the nuclei of SMC5-YFP-OX seedlings following MMS treatment in darkness (Fig. 6a, b). In contrast, SMC5-YFP foci were detected in up to 59% of nuclei in SMC5-YFP-OX/cop1-4 seedlings under the same conditions, indicating that SMC5 recruitment was partially restored, likely due to the accumulation of ADA2b in the cop1-4 background even in darkness. However, the percentage of nuclei containing SMC5-YFP foci fell to only 2% in SMC5-YFP-OX/cop1-4 ada2b seedlings, indicating that COP1 inhibits SMC5 recruitment through ADA2b (Fig. 6a, b).

**Fig. 6: COP1 negatively regulates the recruitment of SMC5 and DNA repair via ADA2b.**

COP1 genetically acts upstream of ADA2b to regulate DNA repair

To further explore the genetic relationship between COP1 and ADA2b, we generated cop1-4 ada2b double mutant via genetic crossing. We treated WT, cop1-4, ada2b, and cop1-4 ada2b mutants with MMS to induce DNA damage under white, blue, and red light, respectively. The results showed that the relative fresh weight of the cop1-4 mutant was significantly higher than that of WT, while the cop1-4 ada2b double mutant, similar to the ada2b mutant, exhibited significantly lower relative fresh weight under all tested light conditions (Fig. 6c–e, Supplementary Fig. 16). These results indicate that the enhanced DNA damage resistance observed in the cop1-4 mutant is dependent on ADA2b. Consistently, in contrast to reduced DNA damage accumulation in cop1-4 nuclei, cop1-4 ada2b double mutant exhibited significantly increased DNA in tail in comet assays after MMS treatment in darkness, similar to the ada2b mutant (Fig. 6f, g). Taken together, these results indicate that COP1 acts upstream of ADA2b in the regulation of DNA repair.

CRYs and phyB partially depend on COP1 in regulating DNA repair

Next, we investigated whether COP1 functions downstream of photoreceptors to regulate DNA repair in response to light. Given our observation that phyA/phyB promote ADA2b accumulation under red/far-red light (Fig. 1e), we examined whether phyA/phyB might modulate DNA repair under these conditions. We treated WT, ada2b, and phyA phyB mutants with UV-C irradiation and DNA damage agents MMS and Zeocin under red light. The results showed that, similar to the ada2b mutant, the relative fresh weight of the phyA phyB double mutant was significantly lower than that of WT (Fig. 7a–f). Similar sensitivity to DNA damage was also observed in phyB mutant under red light (Supplementary Fig. 17). Consistently, comet assays revealed that, compared to WT, the phyB mutant and phyA phyB double mutant exhibited significantly longer DNA tails in the nuclei under red light, indicating increased DNA damage accumulation (Fig. 7g, h, Supplementary Fig. 18). These results suggest that phyB mediates red light to regulate DNA repair. We then generated the phyA phyB ada2b triple mutant by genetic crossing. The phyA phyB ada2b triple mutant showed a similar level of DNA damage to the ada2b single mutant, placing phyA/phyB and ADA2b in the same genetic pathway for red-light-mediated DNA repair (Supplementary Fig. 18). Furthermore, phyA mutant also exhibited more pronounced DNA tail formation in the nuclei under far-red light than WT, suggesting that phyA might also mediate far-red light to regulate DNA repair (Fig. 7i, j).

**Fig. 7: phyA and phyB promote DNA repair under far-red and red light, respectively.**

Having established that phyB is required for DNA repair under red light, we next asked whether red light regulates DNA repair by modulating COP1 activity. We first examined how red light affects COP1-mediated regulation of ADA2b. When etiolated seedlings were transferred from darkness to red light, YFP-ADA2b protein levels, which were initially low in the dark, increased progressively in the WT background (Fig. 1e, Supplementary Fig. 19). In contrast, in the cop1-4 mutant background, YFP-ADA2b was already stabilized in darkness and only increased slightly under red light, suggesting that red light promotes ADA2b accumulation primarily by suppressing COP1 function (Supplementary Fig. 19).

Given that photoreceptors were reported to inhibit COP1-mediated degradation by disrupting its interaction with substrates^20,22, we next tested whether photoreceptors CRYs and phyB could interfere with the COP1-ADA2b association here. Pull-down assays showed that blue-light-activated Myc-CRYs and red-light-activated Myc-phyB, but not dark-adapted Myc-GUS, substantially weakened the interaction between COP1 and ADA2b (Supplementary Fig. 20). Correspondingly, when new protein synthesis was inhibited by CHX, the degradation of YFP-ADA2b was accelerated in cry1 cry2 mutants and in phyA phyB mutants than that in WT background under continuous blue light or red light, respectively (Supplementary Fig. 21). Together, these findings indicate that photoactivated CRYs and phyB likely inhibit COP1-mediated degradation of ADA2b, at least in part, by impairing the COP1-ADA2b interaction, thereby linking light perception to COP1-dependent regulation of DNA repair.

To further explore the genetic relationship between COP1 and the CRYs/phyB photoreceptors in regulating DNA repair, we generated cry1 cry2 cop1-4 triple mutant and phyB cop1-4 double mutant via genetic crossing. We treated these mutants with UV-C irradiation under blue or red light, respectively. The results showed that, after DNA damage treatment under blue light, the relative fresh weight of the cry1 cry2 cop1-4 triple mutant was significantly higher than that of cry1 cry2, but lower than that of cop1-4 (Fig. 8a, b). Similarly, under red light, the relative fresh weight of the phyB cop1-4 double mutant was significantly higher than that of phyB, yet lower than that of cop1-4 (Fig. 8c, d). These results suggest that CRYs and phyB mediate blue and red light, respectively, to regulate DNA repair, at least partially, through COP1.

**Fig. 8: CRYs and phyB mediate blue and red light, respectively, to repair DNA via COP1.**

Discussion

Light is a critical environmental factor that regulates the entire life cycle of plants. Previous studies have shown that CRYs mediate blue light to promote DNA repair^36,38,39. This study provides compelling evidence supporting that COP1 negatively moderates DNA repair in response to light: (1) Light signals induce the accumulation of the DNA repair promoting factor ADA2b (Fig. 1, Supplementary Fig. 1); (2) COP1 interacts with ADA2b and mediates its ubiquitination and degradation via the 26S proteasome pathway (Figs. 2, 3, 5a–c and Supplementary Figs. 2–9); (3) Disruption of COP1 leads to reduced DNA damage accumulation after DNA damage induction (Fig. 4h, i, Supplementary Fig. 13); (4) COP1 mutation enhances plant resistance to DNA damage under multiple light conditions (Fig. 4d–g, Supplementary Fig. 11, 12); (5) The impaired recruitment of SMC5 to DSBs, enhanced plant resistance, and reduced DNA damage accumulation after DNA damage induction caused by the COP1 mutation are all dependent on the function of ADA2b (Fig. 6, Supplementary Fig. 16); (6) COP1 mutation largely reverses the DNA damage hypersensitivity observed in photoreceptor mutants, suggesting that COP1 acts downstream of these photoreceptors in modulating DNA repair (Fig. 8a–d). Collectively, these findings unveil a COP1-ADA2b regulatory module, highlighting COP1’s role as a central switch in light signal transduction and revealing its unexpected function in controlling DNA repair in plants.

DSBs are primarily repaired via two conserved pathways: error-prone NHEJ, which directly ligates DSB ends but often introduces insertions, deletions, or translocations, and error-free HR, which, if overactive, can also lead to recombination between non-allelic repeats in heterochromatin, causing chromosomal rearrangements and aberrations^31,32,40. Thus, DSB repair must strike a delicate balance, as excessive repair can also disrupt genome stability. Additionally, ADA2b also exhibits a highly conserved function in enhancing GCN5-mediated acetyltransferase activity³⁵. If unrestrained, ADA2b/GCN5-mediated histone acetylation leads to the de-repression of transposable elements in heterochromatic regions, thereby compromising genome stability⁴¹. Thus, both the functions on DSB repair and histone acetylation of ADA2b must be tightly regulated to maintain genome stability, and COP1-mediated degradation of ADA2b elegantly fulfills this dual regulatory requirement. COP1 is highly conserved, although no longer light-responsive in mammalian cells, targeting tumor suppressor p53 for degradation in response to DNA damage^42,43. Interestingly, ADA2b is also highly conserved across species, with homologs in yeast and Drosophila also participating in MMS-induced DNA damage⁴⁴, suggesting that a similar COP1-ADA2b-based mechanism may also exist in other organisms to ensure the appropriate DNA repair.

The inhibition of COP1 function by light may be achieved through changes in its nuclear localization or by modulating the formation of COP1/SPAs complexes via photoreceptors to regulate its E3 ubiquitin ligase activity^{13,14,15,16,17,18,19}. The former mechanism is prominent at 12-36 h after light exposure^13,14,21, while the latter occurs within 6 h^15,18,19. Given that ADA2b accumulates within a shorter time window following light exposure (Fig. 1), photoreceptor-mediated regulation of COP1 activity likely plays a primary role in coordinating DNA repair. Disruption of CRYs and phyB increases DNA damage sensitivities in blue and red light, respectively³⁶ (Fig. 7, Supplementary Fig. 17), and these sensitivities are partially dependent on COP1 function (Fig. 8a–d). The intermediate phenotypes observed in cry1 cry2 cop1-4 and phyB cop1-4 mutants may result from the nature of the cop1-4 mutant in them, a weak allele not capable of fully suppressing the photoreceptor mutant phenotypes. It is possible that other factors downstream of photoreceptors cooperate with COP1 in regulating DNA repair. The root of phyA mutant exhibits a hypersensitive response to DNA damage⁴⁵, and we observed significantly longer comet tails in phyA mutant (Fig. 7i, j) along with reduced ADA2b accumulation in phyA phyB mutant (Fig.1e) under far-red light, suggesting that phyA might also mediate far-red light to regulate DNA repair.

Although COP1 activity is inhibited by activated photoreceptors, cop1-4 mutant alleles still exhibit hyper-photomorphogenic phenotypes under light, characterized by shorter hypocotyl, increased anthocyanin accumulation, and enhanced stomata production, indicating that COP1 retains partial function in the light^10,46,47. Since etiolated seedlings exhibit skotomorphogenesis, lack chlorophyll, and fail to produce leaves, we analyzed some DNA damage-related phenotypes in cop1-4 mutant under light conditions. Despite the suppression of COP1 activity in the light, cop1-4 mutant still exhibited significantly greater resistance to DNA damage than WT (Fig. 4d–i; Supplementary Figs. 10–13). This residual DNA damage resistances in light conditions may result from the modest yet functional difference in endogenous ADA2b protein accumulation between cop1-4 and the WT. However, when YFP-ADA2b was overexpressed in both backgrounds, the high protein abundance masked the subtle difference caused by residual COP1 activity under high-intensity white light. Accordingly, while YFP-ADA2b accumulation differed markedly between cop1-4 background and the WT background in darkness, the difference became minimal under high-intensity white light (Fig. 5a–c, Supplementary Fig. 14). Consistent with this, phenotypic differences between YFP-ADA2b overexpression in cop1-4 and the WT background were significant under dim light or darkness but were no longer detectable under high-intensity white light (Fig. 5, Supplementary Fig. 14, and Supplementary Fig. 15). In the dark, cop1-4 mutant displays elongated root, increased root meristem cell numbers, and reduced comet tail compared to WT even in the absence of exogenous DNA damage agents (Fig. 4a–c). This phenotype indicates reduced endogenous DNA damage accumulation in cop1-4 mutant, demonstrating that COP1 may also participate in repairing spontaneously arising DNA lesions during routine growth and developmental processes in darkness.

Furthermore, we found that phyB interacted with ADA2b and SMC5 in yeast (Supplementary Fig. 22), and phyA and phyB were partially co-localized with ADA2b and SMC5 in the same nuclear bodies of plant cells (Supplementary Fig. 23), implying that phyA/phyB might also directly interact with ADA2b/SMC5 to promote DNA repair like CRYs. Darkness suppresses DNA repair via COP1-mediated ADA2b degradation (Fig. 8e, g). In contrast, light may activate photoreceptor-dependent DNA repair through both suppression of COP1 and promotion of recruitment of the SMC5/6 complex (Fig. 8f, h). The CRYs/phyB-COP1 antagonism may act as environmental rheostats: CRYs and phyB can serve as light-dependent “accelerators” promoting DNA repair, while COP1 can function as a darkness-triggered “brake” to suppress DNA repair (Fig. 8e–h). The dynamic balance between these opposing forces ensures optimal DNA repair activity in plants to maintain genome stability, and optimize their growth according to the fluctuating light conditions.

Beyond DNA repair, plants deploy alternative strategies like endoreplication, genome amplification without mitosis, to tolerate DNA damage while preventing mutation propagation^48,49. Given our results showing that COP1 suppresses DNA repair by promoting ADA2b degradation in darkness, and the previous studies demonstrating that COP1 acts to promote endoreplication in skotomorphogenic hypocotyl cells^50,51, we propose that COP1 may mediate a trade-off between DNA damage repair and tolerance in plants. This COP1-driven “toggle switch” might allow germinated seedlings to undergo error-tolerant growth to prioritize rapid soil emergence under darkness, and then shift to error-correcting DNA repair upon light exposure. During skotomorphogenesis, devoid of photosynthesis, subterranean seedlings might prioritize rapid hypocotyl elongation over precise DNA repair according to limited energy supply, likely employ endoreduplication to respond to DNA damage. In addition to preventing the spread of mutations, endoreplication might account for continued growth in the absence of cell division, a “growth-over-repair” strategy critical for soil emergence⁵⁰. After emergence from the soil, plants undergo photomorphogenesis, and shift priorities to lateral-organ growth, especially leaf growth for photosynthesis, which requires meristemoid division and cell proliferation, in addition to cell expansion⁵². Fueled by photosynthesis, plants may invest in high-fidelity repair to sustain division-intensive organogenesis along with daytime challenges, such as pathogen attacks, high solar radiation containing UV light, and photosynthesis-generated reactive oxygen species (ROS)⁴⁹. Plants might orchestrate genome maintenance with developmental and environmental demands through such light-regulated DNA repair paradigm. The conserved COP1-ADA2b module may represent a universal adaptation strategy, implying how life-history strategies are hardwired into molecular circuits, with implications for understanding DNA repair plasticity across species.

Methods

Plant materials and growth conditions

All Arabidopsis thaliana plants used in this study were of the Columbia ecotype. The following mutants and transgenic lines have been described previously^{13,18,33,36,46}: cop1-4, ada2b-3 (SALK_019407), cry1 cry2, phyA-211, phyB-9, GUS-COP1-OX, Myc-CRY1-OX, Myc-CRY2-OX, Myc-phyB-OX, Myc-GUS, SMC5-YFP-OX, YFP-ADA2b-OX and YFP-ADA2b-OX/cry1 cry2. The following lines were generated in this study by genetic crossing: cop1-4 ada2b, cry1 cry2 cop1-4, phyA phyB ada2b, phyB cop1-4, YFP-ADA2b-OX/cop1-4, SMC5-YFP-OX/cop1-4, SMC5-YFP-OX/cop1-4 ada2b, YFP-ADA2b-OX/GUS-COP1-OX. The YFP-ADA2b-OX/phyA phyB line was generated by the floral dip method⁵³. All overexpression transgenes mentioned above are driven by the cauliflower mosaic virus 35S promoter.

Arabidopsis seedlings were grown on half-strength Murashige and Skoog (1/2 MS) medium supplemented with 1% sucrose and 0.8% agar, at 22 °C under indicated light conditions in plant growth chambers (BPC500-2H, Fujian Jiupo Biotechnology Co., Ltd). Light intensity was measured using an ILT2400-A quantum photometer (LI-COR Biosciences).

Yeast two-hybrid assays

Constructs expressing AD-ADA2b, AD-ADA2bN (AA 1-224), and AD-ADA2bC (AA 225-487) were described previously^33,54. The cDNAs encoding COP1 and its various deletion or truncation variants (ΔZn, ΔCoil, ΔZnΔCoil, N282, C283-675, C386-675, and C209-386) were cloned into the DNA-binding domain (BD) vector pGBKT7. The primers used in this study are listed in Supplementary Table1. The combinations of the bait and prey constructs were co-transformed into AH109 yeast cells, and interactions were detected on SD-Leu-Trp-His-Ade (SD-LWHA) medium.

Pull-down assays

The construct expressing GST-ADA2b was described previously³⁶. The cDNA encoding COP1 was cloned into pCold-Trigger Factor (TF) vector (TaKaRa, 3365). His-TF-COP1, His-TF, GST-ADA2b, and GST proteins were expressed in E. coli strain Rosetta.

For the basic GST pull-down assay, bait proteins (GST-ADA2b or GST) were incubated with MagneGST^TM Glutathione Particles (Promega, V8611) in lysis buffer (50 mM Tris-HCl, pH 7.5; 150 mM NaCl; 0.2% Triton-X-100) at 4 °C for 2 h and washed three times. Prey proteins (His-TF-COP1 or His-TF) were then added and incubated at 4 °C for 1 h, followed by three washes. The bait and prey proteins were detected by immunoblotting using anti-GST (GenScript, A00865, 1:1000 dilution) and -His antibodies (GenScript, A00186, 1:1000 dilution), respectively.

For assessment of the effects of CRY1, CRY2, or phyB on the COP1-ADA2b interaction, plant protein extracts were included as effectors. GST-ADA2b bait protein was immobilized on MagneGST Glutathione Particles as described above. His-TF-COP1 prey protein was then added together with effector extracts and incubated at 4 °C for 1 h. Effector extracts were prepared from transgenic seedlings under specified conditions: Myc-CRY1-OX or Myc-CRY2-OX seedlings (dark-adapted for 3 d, pretreated with MG132 for 4 h, and exposed to blue light at 50 μmol/m²/s for 30 min), Myc-phyB-OX seedlings (dark-adapted and MG132-treated, then exposed to red light at 50 μmol/m²/s for 30 min), or Myc-GUS seedlings (dark-adapted and MG132-treated as a control). Following incubation, the beads were washed three times with lysis buffer. The bait, prey, and effector proteins were detected by immunoblotting with anti-GST, -His, or -Myc (Millipore, 05-724, 1:5000 dilution) antibodies, respectively.

Split-LUC assays

The construct expressing ADA2b-nLUC was described previously³⁶. The cDNA fragments of ADA2bN (AA 1-224), ADA2bC (AA 225-487), and COP1 were cloned into the pCambia1300-nLUC and pCambia1300-cLUC vectors respectively. The indicated combinations of GV3101 cells harboring the constructs were mixed and introduced into tobacco (Nicotiana benthamiana) leaves, and the luciferase activity was detected as described previously³⁶.

Protein co-localization analyses

The constructs expressing YFP-ADA2b and SMC5-YFP were described previously³⁶. For transient expression in Nicotiana benthamiana, cDNA fragments encoding ADA2bN (AA 1-224) and ADA2bC (AA 225-487) were cloned into pCambia1300-35S-YFP, and COP1, PHYA, and PHYB cDNA fragments were cloned into pCambia1300-35S-mcherry. The indicated combinations of Agrobacterium tumefaciens GV3101 cells harboring the constructs expressing YFP and mCherry fusion proteins were mixed and introduced into tobacco leaves.

For the co-localization analyses of ADA2b-YFP and endogenous COP1 in Arabidopsis cells, four-day-old white light-grown YFP-ADA2b-OX seedlings were incubated in liquid 1/2 MS containing 100 ppm MMS for 24 h. Seedlings were then fixed in 4% paraformaldehyde (Beyotine, P0099) for 10 min and sliced with a razor blade. Nuclei were isolated using a 40 μm nylon cell strainer (Falcon, 352340). Isolated nuclei were immunostained with the primary antibodies anti-COP1 and -γH2AX (Biolegend, 613402, 1:1000 dilution), followed by incubation with secondary antibodies Alexa Fluor 555-labelled goat anti-mouse (Abcam, ab150114, 1:10000 dilution) and Alexa Fluor 594-labelled anti-rabbit (Invitrogen, A32740, 1:10000 dilution) and stained with DAPI (Yeasen, 36308ES20). Protein co-localization fluorescence signals were detected using confocal microscopy (Leica Stellaris 8).

BiFC assays

The full-length cDNAs of COP1 and ADA2b were cloned into pXY104 and pXY106 vectors to generate COP1-cYFP (pXY104-COP1) and nYFP-ADA2b (pXY106-ADA2b). BiFC assays were performed as described previously⁵⁵ with minor modifications. Agrobacterium tumefaciens GV3101 cultures carrying COP1-cYFP (or cYFP control) and nYFP-ADA2b (or nYFP control) were mixed at a 1:1 ratio and infiltrated into leaves of transgenic tobacco expressing RFP‑H2B. After infiltration, plants were kept in darkness for 24 h, followed by either continued darkness or exposure to white light (80 μmol/m²/s) for an additional 24 h. YFP fluorescence signals were detected using a confocal microscope (Leica Stellaris 8).

co-IP assays

For examining the association between YFP-ADA2b and GUS-COP1 in darkness, GUS-COP1-OX and YFP-ADA2b-OX/GUS-COP1-OX seedlings were grown under white light (80 μmol/m²/s) for 4 d and then adapted in darkness for 3 d. For testing the association of YFP-ADA2b with endogenous COP1 under dark or light conditions, five-day-old white light-grown YFP-ADA2b-OX seedlings and YFP control seedlings were dark-adapted for 3 d, then incubated in liquid 1/2 MS medium containing 50 μM MG132 and 100 ppm MMS for 12 h under continuous darkness or white light (80 μmol/m²/s), respectively. Total proteins were extracted with lysis buffer (50 mM Tris-HCl, pH 7.5; 150 mM NaCl; 0.2% Triton-X-100). Equal amounts of extracted proteins were incubated with anti-GFP agarose beads (Smart-Life Sciences, SA070005) at 4 °C for 2 h, washed 3 times, and then subjected to immunoblotting with anti-GFP (Abmart, M20004H, 1:1000 dilution) and -COP1 (Abclonal, A18844, 1:1000 dilution) antibodies.

Ubiquitination assays

In vitro ubiquitination assays were performed as described previously⁵⁶ with minor modifications. Reaction mixtures (60 μL) contained 50 nM UBE1 (E1, Boston Biochem), 200 nM UbcH5b (E2, Boston Biochem), 10 μg Flag-tagged ubiquitin (Flag-Ub, Boston Biochem), 200 ng GST-ADA2b, and 0.5 μg MBP-COP1 or MBP in reaction buffer (50 mM Tris, pH 7.5, 10 mM MgCl₂, 10 mM ATP, 10 μM ZnCl₂). After incubation at 30 °C for 2 h, reactions were stopped by 5× SDS loading buffer. Ubiquitinated GST-ADA2b was detected by immunoblotting using anti-GST and -Flag (Sigma-Aldrich, F3165, 1:1000 dilution) antibodies.

For in vivo ubiquitination assays of YFP-ADA2b under dark and light conditions, white light-grown YFP-ADA2b-OX and YFP (control) seedlings were dark-adapted for 3 d. YFP-ADA2b-OX seedlings were then incubated in liquid 1/2 MS medium containing 50 μM MG132 and 100 ppm MMS for 12 h under continuous darkness or white light, respectively. YFP seedlings were incubated in the same liquid in darkness as a control. Total proteins were extracted with lysis buffer, and equal amounts of extracted proteins were incubated with anti-GFP agarose beads at 4 °C for 2 h. After three washes, ubiquitination of ADA2b was detected by immunoblotting using anti-GFP and -Ub (Cell Signaling Technology, 3936, 1:1000 dilution) antibodies, respectively.

For in vivo ubiquitination assays of COP1-mediated ADA2b ubiquitination, ten-day-old white light-grown YFP-ADA2b-OX and YFP-ADA2b-OX/cop1-4 seedlings were treated with 50 μM MG132 and adapted in darkness for 12 h. Total proteins were extracted with lysis buffer, and equal amounts of extracted proteins were incubated with anti-GFP agarose beads at 4 °C for 2 h. Following 3 washes, immunoprecipitates were subjected to immunoblotting with anti-GFP, -COP1, and -Ub antibodies.

Cell-free degradation assays

Total proteins were extracted from 5-day-old white light-grown YFP-ADA2b-OX seedlings using degradation buffer (50 mM Tris-HCl, pH 7.5; 10 mM NaCl; 10% glycerol; 0.2% Triton-X-100; 10 mM MgCl₂; 5 mM ATP). Equal extracted protein amounts were treated with 0.5% (v/v) DMSO, 50 μM MG132, or 50 μM MG115 for 1 h, or incubated with 0.5% (v/v) DMSO or 50 μM MG132 for 0, 30, 60, and 120 min. The proteins were detected by immunoblotting using anti-GFP and -ACTIN (Abmart, M20009, 1:1000 dilution) antibodies.

Root length and meristem analysis

Primary root length was measured from the root tip to the hypocotyl base using ImageJ software. For the measurement of root apical meristem region, seedlings were stained with 20 μg/mL propidium iodide (PI) for 10 min in darkness at room temperature, and imaged using a confocal microscope (Leica Stellaris 8). The number of root meristem cells was determined by counting cortical cells from the initial cell adjacent to the quiescent center (QC) to the first elongated cell in the transition zone.

Comet assays

We performed neutral comet assays to assess DSBs. The detailed treatment conditions for seedlings in each experiment (including light conditions, chemical treatments, and sampling time points) are specified in the corresponding figure legends. Below is the general protocol for slide preparation, electrophoresis, and analysis, which was consistently applied across all experiments.

Comet assays were performed using the CometAssay Kit (R&D Systems, 4250-050-K) according to the manufacturer’s protocol. Seedlings, leaves, or roots were rapidly minced in 500 μL 1×PBS buffer containing 20 mM EDTA on ice with fresh razor blades to generate a cell suspension, which was then filtered through a 40 µm nylon mesh. This process, from tissue harvest to the generation of a nucleus suspension, was completed within 20–30 min to minimize spontaneous DNA damage. The filtered nuclear suspension was mixed with low-melting-point agarose (LMAgarose) at a 1:10 ratio, and the mixture was spread onto comet slides. Slides were kept at 4 °C in darkness for 30 min, treated with lysis solution at 4 °C for 30-40 min, washed 3 times with 1×TBE (90 mM Tris-borate, 2 mM EDTA, pH 8.4), and then subjected to electrophoresis. Electrophoresis was performed in the same 1× TBE buffer at 23 V for 10 min at 4 °C. Following gentle washes with distilled water and 70% ethanol (5 min each), slides were air-dried at 37 °C. The comets were visualized by staining with SYBR Gold (Invitrogen, S11494) or DAPI (Yeasen, 36308ES20) and detected by confocal microscopy (Leica Stellaris 8). DNA in tail was automatically quantified using Comet Score 2.0 software (TriTek), with 100-150 nuclei scored per biological replicate.

Statistics and reproducibility

Biological replicates, sample size, and P values can be found in figures, figure legends, and Source Data. Data are presented as mean ± standard deviation, with error bars indicating the standard deviation. Statistical analyses of data were conducted using Microsoft Excel 2021 and GraphPad Prism 9.0. Comparisons between two plant genotypes were performed using unpaired two-tailed Student’s t-test. Comparisons among more than two genotypes were conducted using one-way ANOVA followed by Tukey’s post hoc test. For comparisons involving multiple genotypes under different treatment conditions, two-way ANOVA was performed. Multiple comparisons were adjusted using Šídák’s test for the data presented in Fig. 4f, g, or Tukey’s test for Fig. 4f as recommended by GraphPad Prism 9.0. P values for t-test and adjusted P values for all multiple comparisons are also reported in Source Data. No statistical method was used to predetermine sample size. No data were excluded from the analyses. The experiments were not randomized. The Investigators were not blinded to allocation during experiments and outcome assessment. All the experiments were repeated at least twice with similar results.

Accession numbers

Sequence data from this article can be found in the EMBL/GenBank database or the Arabidopsis Genome Initiative database under the following accession numbers: COP1 (<span type="Italic" name="Emphasis" class="Italic">AT2G32950), ADA2b (AT4G16420), CRY1 (AT4G08920), CRY2 (AT1G04400), phyA (AT1G09570), phyB (AT2G18790), and SMC5 (AT5G15920).

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.

Data availability

All data generated or analyzed in this study are available in this article and supplementary data. Source data are provided with this paper.

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Acknowledgements

We thank Drs Chun-Peng Song, Xing Wang Deng, Chengwei Yang, Yuda Fang, Qin Wang, Jigang Li, and Hongli Lian for their materials and technical assistance. This work was supported by grants from the National Natural Science Foundation of China (Grant No. 32470254 and 32000183 to T.G., and 32370262 to H.-Q.Y.), the National Key R&D Program of China (Grant No. 2024YFA1306702 to H.-Q.Y.), and the Shanghai Engineering Research Center of Plant Germplasm Resources (Grant No. 17DZ2252700 to H.-Q.Y.).

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These authors contributed equally: Li Chen, Liman Diao.

Authors and Affiliations

Shanghai Key Laboratory of Plant Molecular Sciences, Shanghai Collaborative Innovation Center of Plant Germplasm Resources Development, College of Life Sciences, Shanghai Normal University, Shanghai, China
Li Chen, Liman Diao, Jiaqi Ruan, Yanli Deng, Kai Zhang, Yan Guan, Min Liang, Lina Peng, Jiayi Shi, Shilong Zhang, Minqing Liu, Yupeng Li, Zhilei Mao, Wenxiu Wang, Hong-Quan Yang & Tongtong Guo
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
Ling Li

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Li Chen
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Liman Diao
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Jiaqi Ruan
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Yanli Deng
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Kai Zhang
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Yan Guan
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Ling Li
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Min Liang
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Lina Peng
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Shilong Zhang
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Minqing Liu
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Yupeng Li
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Zhilei Mao
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Wenxiu Wang
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Contributions

L.C., T.G., and H.-Q.Y. designed the experiments. L.C., L.D., J.R., Y.D., K.Z., Y.G., L.L., M. Liang, L.P., J.S., S.Z., M. Liu, Y.L., Z.M., W.W., and T.G. carried out the experiments. L.C., L.D., and T.G. collected the data. T.G., L.C., and H.-Q.Y. wrote the manuscript with input from all other authors.

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Correspondence to Tongtong Guo.

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Nature Communications thanks Jian Li and the other anonymous reviewer(s) for their contribution to the peer review of this work. A peer review file is available.

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Chen, L., Diao, L., Ruan, J. et al. The COP1-ADA2b module mediates light regulation of DNA double-strand break repair in Arabidopsis. Nat Commun 17, 3876 (2026). https://doi.org/10.1038/s41467-026-70673-z

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Received: 09 May 2025
Accepted: 27 February 2026
Published: 13 March 2026
Version of record: 29 April 2026
DOI: https://doi.org/10.1038/s41467-026-70673-z