A COP1-HY5-ABI5 module regulates ABA-mediated post-germination developmental arrest

Abscisic Acid (ABA) is a key phytohormone that regulates plant development under stress. ABA induces dormancy in seeds during maturation, whereas its levels and activity gradually decrease as germination and seedling growth progress. Under abiotic stress conditions, elevated levels of ABA inhibit seed germination and/or impose post-germination growth arrest. The transcription factor ABSCISIC ACID INSENSITIVE 5 (ABI5) regulates the interplay between ABA and light signaling to modulate this process. The light-regulated transcription factor ELONGATED HYPOCOTYL 5 (HY5) modulates ABA-mediated inhibition of post-germination development. However, the interrelation between HY5 and ABI5 in regulating post-germination development remains poorly understood. Here, using molecular, genetic, and biochemical approaches, we show that ABI5 and HY5 proteins reciprocally influence each other’s accumulation during early plant development. We further find that ABA induces nuclear accumulation of COP1, which correlates with reduced HY5 levels and enhanced ABI5 accumulation under stress conditions. Together, our results support a model in which a double-negative feedback loop between HY5 and ABI5 contributes to ABA-mediated post-germination growth arrest.

Introduction

Early seedling establishment is a critical stage in the plant life cycle. It is marked by the emergence of the embryonic roots or radicle and the opening and expansion of the cotyledons, after the seed coat breaks during germination. Plants tightly regulate both germination and post-germination development to prevent premature seedling development. However, under stress conditions, the stress hormone ABA can delay the process of early seedling development, causing germinated embryos to remain quiescent, known as post-germination arrest. This arrest is a strategic adaptive response to conserve energy and resources, promoting growth resumption only under optimum growth conditions. The declining ABA gradient demarcates the transition from quiescence to active growth phase. A key molecular player that mediates this process is the transcription factor ABSCISIC ACID INSENSITIVE 5 (ABI5), which also plays a prominent role in integrating ABA response with environmental signals such as light (Xu et al., 2014; Yadukrishnan and Datta, 2021; Li et al., 2022a, 2022b; Zhao et al., 2022).

Light is a critical environmental factor in regulating early seedling development (Chen et al., 2008). Light-responsive factors and ABA signaling components coordinate early seedling development when plants are under stress. The bZIP transcription factor ELONGATED HYPOCOTYL 5 (HY5) is a point of convergence between the light and ABA signaling pathways (Chen et al., 2008). A previous study has shown that HY5 positively regulates ABA signaling, while another study has shown that HY5 suppresses ABA-mediated post-germination growth arrest (Chen et al., 2008; Yadukrishnan et al., 2020a). HY5 protein levels are tightly regulated by the E3 ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), where COP1 ubiquitinates HY5 and targets it for degradation (Osterlund et al., 1999, 2000b, 2000a). Recent studies have indicated that COP1 plays a positive role in regulating ABA signaling. cop1 seedlings exhibit ABA hyposensitivity and establish faster than wild-type seedlings in the presence of ABA (Yadukrishnan et al., 2020b). COP1 physically interacts with ABA-HYPERSENSITIVE DCAF1 (ABD1), a negative regulator of ABI5 abundance, and induces its proteasomal degradation to promote ABI5 stability (Peng et al., 2022). cop1hy5–215 display ABA hypersensitivity similar to that of the hy5–215 suggesting that HY5 is epistatic to COP1 (Yadukrishnan et al., 2020a). HY5 binds to the promoter of ABI5 and activates its transcription (Chen et al., 2008; Xu et al., 2014). However, phenotypic evaluation of the loss-of-function mutants indicated that HY5 suppresses ABA-mediated inhibition of post-germination seedling development (Yadukrishnan et al., 2020a). Together, these studies indicate that the regulatory interactions among HY5 and ABI5 at the protein level might be important in determining their function.

Despite several pieces of evidence suggesting the role of a HY5-ABI5 module in regulating post-germination development, the functional consequences of their molecular-level interactions, particularly how they influence each other’s levels and activity, remain elusive. In this study, we investigated the biochemical and genetic interplay between HY5 and ABI5 during ABA-mediated inhibition of post-germination development, shedding light on additional layers of regulatory complexity within the HY5-ABI5 module.

Materials and methods

Plant materials and growth conditions

In this study, the accession of Arabidopsis thaliana used is Columbia-0 (Col-0). The mutant and reporter lines hy5-215, abi5-8, and 35S:YFP-COP1/cop1–6 have been described previously (Oyama et al., 1997; Zheng et al., 2012; Balcerowicz et al., 2017). The hy5–215 abi5–8 double mutant was generated by genetic crossing. The growth conditions and ABA treatments were similar to those described previously (Yadukrishnan et al., 2020b; Singh and Datta, 2023).

Quantification of germination and seedling establishment

Seeds from the indicated genotypes were harvested simultaneously and surface sterilized, followed by stratification in sterile water for 3 days at 4°C in darkness. Stratified seeds were sown on ½ Murashige and Skoog (MS) agar plates without sucrose, supplemented with either 0 or 1 µM abscisic acid (ABA), and solidified with 0.8% agar. After stratification, the aluminum foil was removed and the plates were transferred to a Percival CU-41L4 growth chamber set to 22°C under a 16 h light/8 h dark photoperiod with white light at 80 µmol m⁻² s⁻¹. Plates were maintained in a vertical orientation throughout the experiments. Germination was scored as the percentage of seeds with fully emerged radicles, and seedling establishment was defined by the presence of open, expanded green cotyledons. For each treatment, more than 500 seeds were analyzed per experiment, and each experiment was independently repeated three times. Representative seedlings were imaged at the indicated time points using a Leica S6E stereomicroscope (www.leica-microsystems.com).

Immunoblotting

Blotting experiments were performed as described by Singh and Datta (2023). Briefly, germinated seeds were crushed in extraction buffer (50 mM Tris–HCl, pH 7.5, 75 mM NaCl, 10 mM EDTA, 10 mM MgCl2, 0.1% Tween 20, 1 mM NaF, and protease inhibitor mix; Sigma) followed by centrifugation for 10 min at 11,000 g at 4°C. 40μg of total protein was loaded per well in SDS-acrylamide/bisacrylamide gel, and proteins were electrophoretically transferred to a PVDF membrane (Millipore). To further examine the mechanism underlying ABA-induced reduction of HY5, germinated seeds were treated with ABA, cycloheximide (CHX), and MG132 either individually or in combination prior to protein extraction. Total protein was isolated and subjected to immunoblotting as described above. Notably, ABA-induced HY5 degradation was prevented in the presence of MG132, indicating proteasome-dependent regulation. The protein was detected using anti-ABI5 (ab98831; Abcam), anti-ACTIN (A0480; Sigma), and anti-HY5 (AS12 1867; Agrisera), respectively.

Confocal laser-scanning microscopy and quantification

Microscopy and quantification were done as mentioned by Balcerowicz et al. (2017). One-day-old germinated seeds expressing 35S::YFP-COP1 were used to study YFP-COP1 subcellular location. Seedlings were stained with 1 µg/mL DAPI and mounted in water. Imaging was performed using an Olympus live cell microscope at 405 and 488 nm excitation wavelengths. Confocal laser-scanning microscopy stacks were analyzed using Fiji, and fluorescence intensity was quantified for 2 to 20 nuclei per seed. A total of 10 seedlings per genotype were examined. Post-germination seedlings expressing proHY5:HY5-YFP were imaged with an excitation wavelength of 488 nm, and HY5 protein accumulation was detected based on YFP fluorescence.

Chromatin immunoprecipitation-qPCR

ChIP assay is performed as previously described (Komar et al., 2016; Yadukrishnan et al., 2020b; Singh and Datta, 2023). Briefly, 1 g of seeds from each genotype (Col-0, hy5-215, abi5-8) were grown on 0.5×MS ±1 µM ABA. Germinated tissues were cross-linked with 1% formaldehyde, and chromatin was extracted, sonicated (4 cycles, 30 s on/off, 4°C), and 10% saved as input. >10 µg chromatin was immunoprecipitated, followed by reverse cross-linking, DNA purification, and qPCR analysis using the % input method. hy5–215 seeds were from Prof. Magnus Holm; abi5–8 from ABRC.

Statistical analysis

All statistical analyses were carried out using GraphPad Prism 10 and Microsoft Excel. Statistical significance was assessed using Welch’s t-test.

Results

ABA oppositely regulates ABI5 and HY5 protein accumulation

Early seedling development under light conditions is known to be regulated by the light-responsive transcription factor HY5 (Gangappa and Botto, 2016). Under stress conditions, ABA induces developmental arrest via the action of ABI5 (Finkelstein and Lynch, 2000). To investigate the regulatory dynamics between light and ABA during early development, we examined the protein levels of HY5 and ABI5 across various stages spanning from seed maturation to seedling establishment, including dry silique (DSL), dry seeds (DSD), imbibed seeds (IS), stratified seeds (SS), pre-germination seeds (PRGS), germinated seeds (GS), and post-germination seedlings (PGS) (Figure 1A). These developmental stages were selected to assess the accumulation patterns of HY5 and ABI5 proteins in relation to fluctuating endogenous ABA levels, high in DSL and DSD, and progressively decreasing as the seeds are exposed to light and proceed through germination and seedling establishment. Immunoblotting with anti-ABI5 antibody indicated high ABI5 levels in dry siliques, dry seeds, imbibed seeds, and stratified seeds, followed by a decline during germination and post-germination development (Figure 1A). Conversely, immunoblotting with anti-HY5 antibody indicated low HY5 levels in mature, dry, imbibed, and stratified seeds, notably increasing during germination and post-germination development (Figure 1A). These results suggested that ABI5 and HY5 exhibit contrasting accumulation patterns during germination and early seedling development. To investigate the effect of ABA on HY5 accumulation, we treated germinated seeds (GS) and post-germination seedlings (PGS) with 10 μM ABA for 3 hours and examined HY5 protein levels. ABA treatment caused a decrease in HY5 accumulation at both stages (Figure 1B). When we used proHY5:HY5-YFP, ABA treatment reduced HY5 accumulation in post-germination seedlings (PGS) (Supplementary Figure S1).

Figure 1

Figure 1. ABA oppositely regulates ABI5 and HY5 protein accumulation. (A) Immunoblot showing the ABI5 and HY5 protein accumulation in consecutive developmental stages. Total protein was harvested from dry silique (Stage 18, yellow and dry silique; DSL), dry seeds (stage 19-20, seeds fall from the replum; DSD), imbibed seeds (3 hours of water imbibition; IS), stratified seeds (3 days in dark at 4 °C; SS), pre-germination seeds (12 hours after stratification; PRGS), germinated seeds (24 hours after stratification; GS), and post-germination seedlings (48 hours after stratification; PGS) during morning hours (ZT2) and subjected to immunoblotting using antibodies against ABI5 (ab98831; Abcam), and HY5 (Agrisera; AS12-1867). (B) Immunoblot showing HY5 protein accumulation. Germinated seeds (GS) and post-germination seedlings (PGS) were treated with 10µM of ABA (+) or mock (-) for 3 hours, and total protein was immunoblotted using anti-HY5 antibody. (C) Immunoblot showing the levels of ABI5 protein in Col-0 and hy5-215. Stratified seeds were sown on 1µM ABA plates, and samples were harvested daily until day four. Total protein was harvested and subjected to immunoblotting using an antibody against ABI5. Anti-ACTIN was used as a sample loading control. (D) Immunoblot showing HY5 protein accumulation in Col-0 and abi5-8. The stratified seeds were treated as in (A) and subjected to immunoblotting using anti-HY5 antibody. Anti-ACTIN was used as a sample loading control. In (C, D) seed images on the top of each day represent the developmental stage. (E-I) ChIP qPCR showing the enrichment of ABI5 (E-G) on the promoter elements of ABI5, EM1, EM6, and HY5 (H, I) on RBCS and HY5 promoter in the presence of ABA; statistical significance was determined using a t-test. Asterisks represent statistically significant differences (****P < 0.0001, ***P < 0.001, **P < 0.01, *P < 0.05) as determined by Welch's t-test. ns, non significant.

Given the opposite accumulation patterns of HY5 and ABI5 during early stages of development, we investigated whether the two proteins regulate each other’s abundance. We sowed stratified seeds of Col-0 and hy5–215 on 1μM ABA plates and collected tissue over a four-day period to examine ABI5 levels. On day one, the levels of ABI5 protein were the same in both genotypes (Figure 1C). Although we had observed that ABI5 levels gradually decrease during germination and post-germination development in the absence of ABA (Figure 1A), treatment with ABA caused a gradual increase in ABI5 accumulation during these stages (Figure 1C). From day two onwards, hy5–215 consistently showed a stronger ABI5 signal compared to Col-0 in the immunoblots, suggesting that HY5 may negatively influence ABI5 protein accumulation during post-germination development (Figure 1C). These findings suggest that although HY5 transcriptionally activates ABI5, it might suppress the protein abundance of ABI5 through additional regulatory mechanisms. To investigate whether ABI5 reciprocally regulates HY5 protein abundance, we performed a similar experiment using Col-0 and abi5–8 grown on 1 μM ABA plates and monitored HY5 protein levels from day 1 to day 4. HY5 protein accumulation gradually increased in Col-0 over this period, while in abi5-8, HY5 consistently showed a stronger signal across all stages examined. (Figure 1D). These results suggest that ABI5 and HY5 reciprocally control their protein abundance during post-germination development. To gain deeper insights into the mechanism by which ABA triggers the decrease of HY5 protein levels, we treated germinated seeds with ABA, cycloheximide (CHX), and MG132 separately and in combinations. ABA-induced decrease in HY5 levels did not occur in the presence of MG132, a proteasome inhibitor.

In contrast, treatment with cycloheximide, a translation inhibitor, did not affect the ABA-induced decrease in HY5 protein levels (Supplementary Figure S2A). Treatment with either cycloheximide or MG132 or their combination in the absence of ABA did not alter HY5 protein levels (Supplementary Figure S2A). These results suggest that ABA triggers the degradation of HY5 protein via the 26S proteasomal pathway. We next examined how ABA influences HY5 binding to the ABI5 promoter, a known HY5 target, during early post-germination development before seedling establishment. ChIP-qPCR analysis revealed that HY5 enrichment at the ABI5 promoter was reduced upon ABA treatment (Supplementary Figure S3A). To further investigate the interplay between HY5 and ABI5 in regulating each other’s binding to the target promoters, we performed ChIP-qPCR using 4-day-old seedlings, using the promoter binding elements as shown in Supplementary Figure S4A (Carles et al., 2002; Chakraborty et al., 2019). We observed that ABI5 shows greater enrichment at its target promoters in the hy5 mutant (Figures 1E-G), while conversely, HY5 exhibits stronger binding to the RBCS and HY5 promoters in the absence of ABI5 (Figures 1H, I). These results indicate that HY5 and ABI5 do not require each other for binding to their respective target promoters.

ABI5 acts genetically downstream of HY5

Although the DNA-protein and protein-protein interactions between ABI5 and HY5 have been shown previously (Bhagat et al., 2021; Wang et al., 2021), it is still unclear how they genetically interact to regulate ABA response during post-germination development. Therefore, we generated hy5-215abi5–8 double mutant and examined its seedling establishment rates in +/- 1μM ABA. In -ABA, all genotypes achieved 100% seedling establishment by day 3 (Figures 2A, B). In +ABA, hy5–215 and abi5–8 displayed ABA hypersensitivity and hyposensitivity, respectively, while hy5-215abi5–8 showed ABA-hyposensitive response similar to that of abi5-8, indicating that ABI5 acts downstream of HY5 (Figures 2C, D).

Figure 2

Figure 2. ABI5 acts genetically downstream of HY5. (A, C) Representative images of 6-day-old seedlings of Col-0, hy5-215, abi5-8, hy5-215abi5–8 grown on a 1/2 Murashige & Skoog (MS) plate supplemented with A, 0 μM ABA and C, 1 μM ABA. (B, D) Seedling establishment rate in B, 0 μM ABA and D, 1 μM ABA for up to 6 days. After stratification, the plates were kept in long days (16 h of light/8 h of dark) under 80 μmol m^-2 s^-1 white light. In (B, D) error bars represent SE of three independent experiments with >500 seeds.

ABI5 and HY5 play opposite roles in regulating seedling establishment after germination

HY5 protein levels are tightly regulated via ubiquitination and proteasomal degradation by the E3 ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) (Osterlund et al., 2000a, 2000b). cop1 mutants display decreased ABA sensitivity during post-germination development in both light and dark conditions, indicating that COP1 positively regulates ABA signaling (Yadukrishnan et al., 2020b). ABA sensitivity of cop1-4hy5–215 is similar to hy5-215, suggesting that HY5 acts downstream to COP1 in regulating ABA response during post-germination growth (Yadukrishnan et al., 2020a). We asked if the ABA-induced degradation of HY5 during post-germination development is COP1-dependent. To test this, we estimated HY5 protein levels in germinated seeds of cop1–4 in +/-ABA conditions. ABA treatment failed to induce degradation of HY5 in cop1-4, indicating that COP1 is required for the ABA-induced degradation of HY5 (Figure 3A). To examine how ABA affects the accumulation of COP1 protein during post-germination development, we probed the levels of COP1 in the germinated seeds of 35S:YFP-COP1/cop1–6 and observed similar levels in the presence and absence of ABA (Figure 3B).

Figure 3

Figure 3. ABI5 and HY5 play opposite roles in regulating seedling establishment after germination. (A) Immunoblot showing HY5 protein accumulation in Col-0 and cop1–4 in the absence and presence of ABA. Germinated seeds of Col-0 and cop1–4 were transferred to 10µM ABA, and total protein was immunoblotted using anti-HY5 antibody. Anti-ACTIN antibody was used for the sample loading control. (B) Immunoblot showing YFP-COP1 protein abundance in the presence and absence of ABA in 35S:YFP-COP1/cop1–6 line. Germinated seeds were treated with 10μM ABA or mock for 3 hours and immunoblotted using Anti-GFP antibody. (C) ABA treatment induces the nuclear accumulation of COP1 in germinated seeds. 35S:YFP-COP1/cop1–6 germinated seeds were treated with mock (methanol) and 10µM ABA for 3 hours. YFP signals were observed under a confocal laser scanning microscope. Bar = 10µm. 4’,6-diamidino-2-phenylindole (DAPI) staining shows the nuclei of the cells. (D) Relative intensity of YFP fluorescence signals from germinated seeds of 35S:YFP-COP1/cop1–6 treated with (+) and without (-) ABA. For each treatment, 10 germinated seeds were observed, and for each sample, images from different imaging depths were stacked together (Z-stacks). Error bars represent SE from at least 60 confocal images. Asterisks represent statistically significant differences (**P < 0.01; *P < 0.05) as determined by Welch’s t-test. (E) Model showing the ABA-mediated regulation of early seedling development by the COP1-HY5-ABI5 module. Flat headlines indicate inhibition, dotted lines with arrows or flat heads indicate processes where mechanistic details are yet to be investigated.

Darkness promotes the nuclear localization of COP1, which leads to the degradation of several light-responsive transcription factors, including HY5 (Von Arnim and Deng, 1994). Recent evidence suggests that ABA promotes nuclear exclusion of COP1 during seed germination, whereas it enhances nuclear localization of COP1 in dark-grown seedlings (Chen et al., 2022; Peng et al., 2022). Together, these studies underscore the diverse regulation of COP1’s nucleocytoplasmic partitioning by ABA in response to varying developmental and environmental conditions. To test whether ABA influences the localization of COP1 under cycling light conditions, we treated germinated seeds of 35S:YFP-COP1/cop1–6 with ABA for 3 hours and monitored the nucleocytoplasmic localization of YFP-COP1 using confocal microscopy. We observed that ABA enhances the nuclear localization of COP1 in germinated seeds (Figures 3C, D). These results suggest that the enhanced nuclear localization of COP1 in the presence of ABA might lead to the degradation of HY5, promoting the post-germination growth arrest. Together, our results suggest that HY5 counteracts ABA-mediated inhibition of post-germination development by suppressing ABI5 levels, whereas ABI5 restricts HY5 levels, forming a double negative feedback loop (Figure 3E).

Discussion

In the presence of ABA, HY5 is degraded in a COP1-dependent manner. The precise molecular mechanism behind the mutually antagonistic action of HY5 and ABI5 remains to be elucidated. Previous studies have postulated that HY5 modulates ABA signaling primarily by activating the transcription of ABI5 (Chen et al., 2008). However, we recently showed that the loss of function of HY5 leads to ABA hypersensitivity during post-germination growth, indicating the negative regulatory role of HY5 on ABA response during early seedling development (Yadukrishnan et al., 2020a). In the current study, we have presented genetic evidence that HY5 controls ABA response in an ABI5-dependent manner (Figure 2). We have observed an enhanced accumulation of ABI5 in hy5 mutants during post-germination growth, which is in agreement with the ABA hypersensitive phenotype of hy5 (Figure 1).

Additionally, our ChIP results showed reduced HY5 enrichment at the ABI5 promoter in the presence of ABA (Supplementary Figure S3). These findings suggest that during the post-germinative phase, ABA may promote ABI5 expression independently of HY5-possibly through ABI5 itself or other transcriptional regulators. The previously known HY5-ABI5 positive transcriptional module fails to explain the negative effect of HY5 on ABI5 protein accumulation. Considering the recent reports on the physical interaction between ABI5 and HY5 (Bhagat et al., 2021; Wang et al., 2021), our findings raise the possibility that HY5 may influence ABI5 levels and/or activity through protein–protein interaction. Future studies disrupting the ABI5–HY5 interaction and testing its effect on ABI5 stability will be important to further evaluate this hypothesis.

Another interesting unresolved question is how ABA promotes the nuclear localization of COP1. In addition to ABA, endoplasmic reticulum (ER) stress and high temperature have decreased HY5 levels by enhancing COP1 nuclear localization (Park et al., 2017; Kang et al., 2021). Therefore, the COP1-HY5 module is a common plant mechanism that activates adaptive responses under different stress conditions. However, its regulation may differ depending on the specific environmental context, likely involving additional upstream or parallel regulatory factors. The different downstream targets of HY5 may determine the physiological effects regulated by this module. Elevated ABA levels are a hallmark response in plants growing under abiotic stress conditions. Our study demonstrates that the COP1-HY5 module acts as a molecular rheostat that fine-tunes ABI5 protein accumulation in response to ABA levels during early seedling development. A potential double-negative feedback loop between HY5 and ABI5 may optimize the ABI5-mediated developmental checkpoint that regulates seedling establishment under abiotic stress conditions, possibly linking environmental light cues to the ABA signaling pathway.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Author contributions

DS: Conceptualization, Data curation, Methodology, Software, Validation, Writing – original draft, Writing – review & editing. PY: Writing – original draft, Writing – review & editing, Resources. PR: Writing – review & editing, Resources. SD: Conceptualization, Funding acquisition, Investigation, Project administration, Resources, Supervision, Writing – original draft, Writing – review & editing.

Funding

The author(s) declare financial support was received for the research and/or publication of this article. SD acknowledges the support from the Department of Biotechnology (BT/HRD/NBA-NWB/39/2020-21(8)) and SERB (STR/2021/000046), Govt. of India.

Acknowledgments

DS, PY, and PR acknowledge IISER Bhopal, DBT, and CSIR, Govt. of India, respectively, for their PhD fellowships. PY acknowledges IISc Bengaluru for the C.V. Raman Postdoctoral Fellowship.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declare that no Generative AI was used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fphgy.2025.1675932/full#supplementary-material

References

Balcerowicz M., Kerner K., Schenkel C., and Hoecker U. (2017). SPA proteins affect the subcellular localization of COP1 in the COP1/SPA ubiquitin ligase complex during photomorphogenesis. Plant Physiol. 174, 1314–1321. doi: 10.1104/PP.17.00488

PubMed Abstract | Crossref Full Text | Google Scholar

Bhagat P. K., Verma D., Sharma D., and Sinha A. K. (2021). HY5 and ABI5 transcription factors physically interact to fine tune light and ABA signaling in Arabidopsis. Plant Mol. Biol. 107, 117–127. doi: 10.1007/S11103-021-01187-Z

PubMed Abstract | Crossref Full Text | Google Scholar

Carles C., Bies-Etheve N., Aspart L., Léon-Kloosterziel K. M., Koornneef M., Echeverria M., et al. (2002). Regulation of Arabidopsis thaliana Em genes: role of ABI5. Plant J. 30, 373–383. doi: 10.1046/J.1365-313X.2002.01295.X

PubMed Abstract | Crossref Full Text | Google Scholar

Chakraborty M., Gangappa S. N., Maurya J. P., Sethi V., Srivastava A. K., Singh A., et al. (2019). Functional interrelation of MYC2 and HY5 plays an important role in Arabidopsis seedling development. Plant J. 99, 1080–1097. doi: 10.1111/TPJ.14381

PubMed Abstract | Crossref Full Text | Google Scholar

Chen Q.B., Wang W. J., Zhang Y., Zhan Q., Liu K., Botella J. R., et al. (2022). Abscisic acid-induced cytoplasmic translocation of constitutive photomorphogenic 1 enhances reactive oxygen species accumulation through the HY5-ABI5 pathway to modulate seed germination. Plant Cell Environ. 45, 1474–1489. doi: 10.1111/PCE.14298

PubMed Abstract | Crossref Full Text | Google Scholar

Chen H., Zhang J., Neff M. M., Hong S. W., Zhang H., Deng X. W., et al. (2008). Integration of light and abscisic acid signaling during seed germination and early seedling development. Proc. Natl. Acad. Sci. U.S.A. 105, 4495–4500. doi: 10.1073/pnas.0710778105

PubMed Abstract | Crossref Full Text | Google Scholar

Finkelstein R. R. and Lynch T. J. (2000). The arabidopsis abscisic acid response gene ABI5 encodes a basic leucine zipper transcription factor. Plant Cell 12, 599–609. doi: 10.1105/TPC.12.4.599

PubMed Abstract | Crossref Full Text | Google Scholar

Gangappa S. N. and Botto J. F. (2016). The multifaceted roles of HY5 in plant growth and development. Mol. Plant 9, 1353–1365. doi: 10.1016/j.molp.2016.07.002

PubMed Abstract | Crossref Full Text | Google Scholar

Kang C. H., Lee E. S., Nawkar G. M., Park J. H., Wi S. D., Bae S.B., et al. (2021). Constitutive photomorphogenic 1 enhances er stress tolerance in arabidopsis. Int. J. Mol. Sci. 22, 10772. doi: 10.3390/IJMS221910772/S1

PubMed Abstract | Crossref Full Text | Google Scholar

Komar D. N., Mouriz A., Jarillo J. A., and Piñeiro M. (2016). Chromatin immunoprecipitation assay for the identification of arabidopsis protein-DNA Interactions In Vivo. J. Vis. Exp. 14, e53422. doi: 10.3791/53422

PubMed Abstract | Crossref Full Text | Google Scholar

Li Z., Luo X., Wang L., and Shu K. (2022a). ABSCISIC ACID INSENSITIVE 5 mediates light–ABA/gibberellin crosstalk networks during seed germination. J. Exp. Bot. 73, 4674–4682. doi: 10.1093/JXB/ERAC200

PubMed Abstract | Crossref Full Text | Google Scholar

Li Z., Sheerin D. J., Von Roepenack-Lahaye E., Stahl M., and Hiltbrunner A. (2022b). The phytochrome interacting proteins ERF55 and ERF58 repress light-induced seed germination in Arabidopsis thaliana. Nat. Commun. 13, 1656. doi: 10.1038/S41467-022-29315-3

PubMed Abstract | Crossref Full Text | Google Scholar

Osterlund M. T., Ang L.-H., and Deng X. W. (1999). The role of COP1 in repression of Arabidopsis photomorphogenic development. Trends Cell Biol. 9, 113–118. doi: 10.1016/S0962-8924(99)01499-3

PubMed Abstract | Crossref Full Text | Google Scholar

Osterlund M. T., Hardtke C. S., Wei N., and Deng X. W. (2000a). Targeted destabilization of HY5 during light-regulated development of Arabidopsis. Nature 405, 462–466. doi: 10.1038/35013076

PubMed Abstract | Crossref Full Text | Google Scholar

Osterlund M. T., Wei N., and Deng X. W. (2000b). The roles of photoreceptor systems and the COP1-targeted destabilization of HY5 an light control of arabidopsis seedling development. Plant Physiol. 124, 1520–1524. doi: 10.1104/pp.124.4.1520

PubMed Abstract | Crossref Full Text | Google Scholar

Oyama T., Shimura Y., and Okada K. (1997). The Arabidopsis HY5 gene encodes a bZIP protein that regulates stimulus-induced development of root and hypocotyl. Genes Dev. 11, 2983–2995. doi: 10.1101/gad.11.22.2983

PubMed Abstract | Crossref Full Text | Google Scholar

Park Y.-J., Lee H.-J., Ha J.-H., Kim J. Y., and Park C.-M. (2017). COP1 conveys warm temperature information to hypocotyl thermomorphogenesis. New Phytol. 215, 269–280. doi: 10.1111/nph.14581

PubMed Abstract | Crossref Full Text | Google Scholar

Peng J., Wang M., Wang X., Qi L., Guo C., Li H., et al. (2022). COP1 positively regulates ABA signaling during Arabidopsis seedling growth in darkness by mediating ABA-induced ABI5 accumulation. Plant Cell 34, 2286–2308. doi: 10.1093/PLCELL/KOAC073

PubMed Abstract | Crossref Full Text | Google Scholar

Singh D. and Datta S. (2023). BBX30/miP1b and BBX31/miP1a form a positive feedback loop with ABI5 to regulate ABA-mediated postgermination seedling growth arrest. New Phytol. 238, 1908–1923. doi: 10.1111/NPH.18866

PubMed Abstract | Crossref Full Text | Google Scholar

Von Arnim A. G. and Deng X. W. (1994). Light inactivation of Arabidopsis photomorphogenic repressor COP1 involves a cell-specific regulation of its nucleocytoplasmic partitioning. Cell 79, 1035–1045. doi: 10.1016/0092-8674(94)90034-5

PubMed Abstract | Crossref Full Text | Google Scholar

Wang T. J., Huang S., Zhang A., Guo P., Liu Y., Xu C., et al. (2021). JMJ17–WRKY40 and HY5–ABI5 modules regulate the expression of ABA-responsive genes in Arabidopsis. New Phytol. 230, 567–584. doi: 10.1111/NPH.17177

PubMed Abstract | Crossref Full Text | Google Scholar

Xu D., Li J., Gangappa S. N., Hettiarachchi C., Lin F., Andersson M. X., et al. (2014). Convergence of light and ABA signaling on the ABI5 promoter. PloS Genet. 10. doi: 10.1371/journal.pgen.1004197

PubMed Abstract | Crossref Full Text | Google Scholar

Yadukrishnan P. and Datta S. (2021). Light and abscisic acid interplay in early seedling development. New Phytol. 229, 763–769. doi: 10.1111/nph.16963

PubMed Abstract | Crossref Full Text | Google Scholar

Yadukrishnan P., Rahul P. V., and Datta S. (2020a). HY5 suppresses, rather than promotes, ABA-mediated inhibition of post-germination seedling development. Plant Physiol. 159, 00783.2020. doi: 10.1104/pp.20.00783

PubMed Abstract | Crossref Full Text | Google Scholar

Yadukrishnan P., Rahul P. V., Ravindran N., Bursch K., Johansson H., and Datta S. (2020b). CONSTITUTIVELY PHOTOMORPHOGENIC1 promotes ABA-mediated inhibition of post-germination seedling establishment. Plant J. 103, 481–496. doi: 10.1111/tpj.14844

PubMed Abstract | Crossref Full Text | Google Scholar

Zhao H., Zhang Y., and Zheng Y. (2022). Integration of ABA, GA, and light signaling in seed germination through the regulation of ABI5. Front. Plant Sci. 13. doi: 10.3389/FPLS.2022.1000803

PubMed Abstract | Crossref Full Text | Google Scholar

Zheng Y., Schumaker K. S., and Guo Y. (2012). Sumoylation of transcription factor MYB30 by the small ubiquitin-like modifier E3 ligase SIZ1 mediates abscisic acid response in Arabidopsis thaliana. Proc. Natl. Acad. Sci. U.S.A. 109, 12822–12827. doi: 10.1073/PNAS.1202630109

PubMed Abstract | Crossref Full Text | Google Scholar