{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,23]],"date-time":"2026-07-23T05:35:46Z","timestamp":1784784946188,"version":"3.55.0"},"reference-count":49,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T00:00:00Z","timestamp":1772755200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006769","name":"Russian Science Foundation","doi-asserted-by":"publisher","award":["25-14-00037"],"award-info":[{"award-number":["25-14-00037"]}],"id":[{"id":"10.13039\/501100006769","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012190","name":"Ministry of Science and Higher Education of the Russian Federation","doi-asserted-by":"crossref","award":["126012615950-2"],"award-info":[{"award-number":["126012615950-2"]}],"id":[{"id":"10.13039\/501100012190","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Plants respond to ultraviolet B radiation (280\u2013320 nm) with an integrated reaction that includes the reception of the acting stress factor, followed by the generation of reactive oxygen species and damage to macromolecules and membrane structures, as well as changes in cellular metabolism and the formation of protective systems. However, the involvement of key UV-B\u2013related signalling components such as HY5, SPA1 and BIC1 or BIC2 proteins in physiological, biochemical and molecular responses remains insufficiently understood. The effects of 8, 16 and 24 h of UV-B exposure (within an 8 h photoperiod over three days) on the net photosynthetic rate (Pn), chlorophyll fluorescence parameters Y(II) and Fv\/Fm, reflecting the functional state of PSII, nonphotochemical quenching (NPQ), pigment contents (Chl(a+b), carotenoids, anthocyanins and UV-absorbing pigments (UAPs) and the expression of key light-induced genes in wild-type Arabidopsis thaliana and spa1, bic1,2 and hy5 mutants were studied. UV-B irradiation resulted in a gradual reduction in the Pn, Y(II), Fv\/Fm values and Chl(a+b) but caused a marked increase in the anthocyanin and UAP contents and only minor changes in the carotenoid content. The hy5 mutant presented the lowest net photosynthetic rate (Pn), chlorophyll fluorescence parameters, and chlorophyll and carotenoid contents under all the UV-B exposures. In addition, the accumulation of anthocyanins and UAPs during UV-B treatment was consistently the lowest in hy5. After any UV-B exposure, the highest accumulation of UAPs and anthocyanins was observed in the spa1 mutant, whereas the highest Pn values were detected after 24 h in bic1,2. One of the reasons for the reduced photosynthetic activity and antioxidant capacity in hy5 may be the lower expression levels of CHS and PAL in this variety than in the other genotypes. Our results indicate that HY5 is required to maintain antioxidant responses and photosynthetic performance under repeated daytime UV-B exposure (16.8 kJ m\u22122 per day). In contrast, BIC1, BIC2, and SPA1 also contribute to UV-B tolerance, but through distinct regulatory mechanisms and to a lesser extent.<\/jats:p>","DOI":"10.3390\/ijms27052436","type":"journal-article","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T13:00:02Z","timestamp":1772802002000},"page":"2436","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Involvement of the Light Signalling Components HY5 and BIC1,2 and SPA1 in Plant Responses to Elevated Daytime UV-B Doses"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9945-5504","authenticated-orcid":false,"given":"Pavel","family":"Pashkovskiy","sequence":"first","affiliation":[{"name":"K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-4660-8449","authenticated-orcid":false,"given":"Anna","family":"Abramova","sequence":"additional","affiliation":[{"name":"K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5853-7834","authenticated-orcid":false,"given":"Mikhail","family":"Vereshchagin","sequence":"additional","affiliation":[{"name":"K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vladimir V.","family":"Kuznetsov","sequence":"additional","affiliation":[{"name":"K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vladimir D.","family":"Kreslavski","sequence":"additional","affiliation":[{"name":"Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Russia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Kosobryukhov, A., Khudyakova, A., and Kreslavski, V. (2020). Impact of UV Radiation on Photosynthetic Apparatus: Adaptive and Damaging Mechanisms. Plant Ecophysiology and Adaptation Under Climate Change: Mechanisms and Perspectives I: General Consequences and Plant Responses, Springer.","DOI":"10.1007\/978-981-15-2156-0_18"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Singh, V.P., Singh, S., Prasad, S.M., and Parihar, P. (2017). A Review on Responses of Plants to UV-B Radiation Related Stress. UV-B Radiation, Wiley.","DOI":"10.1002\/9781119143611"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1824","DOI":"10.1111\/nph.18468","article-title":"Mechanisms of UV-B Light-induced Photoreceptor UVR8 Nuclear Localization Dynamics","volume":"236","author":"Fang","year":"2022","journal-title":"New Phytol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1147","DOI":"10.1111\/j.1751-1097.2009.00579.x","article-title":"UV-B Action Spectrum for UVR8-Mediated HY5 Transcript Accumulation in Arabidopsis","volume":"85","author":"Brown","year":"2009","journal-title":"Photochem. Photobiol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"590","DOI":"10.1007\/s13562-020-00623-3","article-title":"HY5-COP1: The Central Module of Light Signaling Pathway","volume":"29","author":"Bhatnagar","year":"2020","journal-title":"J. Plant Biochem. Biotechnol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1353","DOI":"10.1016\/j.molp.2016.07.002","article-title":"The Multifaceted Roles of HY5 in Plant Growth and Development","volume":"9","author":"Gangappa","year":"2016","journal-title":"Mol. Plant"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/j.pbi.2017.03.015","article-title":"The Activities of the E3 Ubiquitin Ligase COP1\/SPA, a Key Repressor in Light Signaling","volume":"37","author":"Hoecker","year":"2017","journal-title":"Curr. Opin. Plant Biol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"16669","DOI":"10.1073\/pnas.1316622110","article-title":"Conversion from CUL4-Based COP1\u2013SPA E3 Apparatus to UVR8\u2013COP1\u2013SPA Complexes Underlies a Distinct Biochemical Function of COP1 under UV-B","volume":"110","author":"Huang","year":"2013","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2311","DOI":"10.1111\/nph.17332","article-title":"Direct Phosphorylation of HY5 by SPA Kinases to Regulate Photomorphogenesis in Arabidopsis","volume":"230","author":"Wang","year":"2021","journal-title":"New Phytol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1323","DOI":"10.1038\/s41467-020-15133-y","article-title":"Cryptochrome-Mediated Blue-Light Signalling Modulates UVR8 Photoreceptor Activity and Contributes to UV-B Tolerance in Arabidopsis","volume":"11","author":"Tissot","year":"2020","journal-title":"Nat. Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1382","DOI":"10.1093\/plphys\/kiab162","article-title":"Perception of Solar UV Radiation by Plants: Photoreceptors and Mechanisms","volume":"186","author":"Rai","year":"2021","journal-title":"Plant Physiol."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Ponnu, J., and Hoecker, U. (2022). Signaling Mechanisms by Arabidopsis Cryptochromes. Front. Plant Sci., 13.","DOI":"10.3389\/fpls.2022.844714"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1007\/s44154-022-00076-9","article-title":"Plant Responses to UV-B Radiation: Signaling, Acclimation and Stress Tolerance","volume":"2","author":"Chen","year":"2022","journal-title":"Stress Biol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1038\/emboj.2009.4","article-title":"Interaction of COP1 and UVR8 Regulates UV-B-Induced Photomorphogenesis and Stress Acclimation in Arabidopsis","volume":"28","author":"Favory","year":"2009","journal-title":"EMBO J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"16366","DOI":"10.1073\/pnas.1210898109","article-title":"C-Terminal Region of the UV-B Photoreceptor UVR8 Initiates Signaling through Interaction with the COP1 Protein","volume":"109","author":"Cloix","year":"2012","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1016\/B978-0-12-801922-1.00007-5","article-title":"Cryptochrome-Mediated Light Responses in Plants","volume":"35","author":"Wang","year":"2014","journal-title":"Enzymes"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Ponnu, J., and Hoecker, U. (2021). Illuminating the COP1\/SPA Ubiquitin Ligase: Fresh Insights into Its Structure and Functions During Plant Photomorphogenesis. Front. Plant Sci., 12.","DOI":"10.3389\/fpls.2021.662793"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.jphotobiol.2014.02.004","article-title":"Impact of Increasing Ultraviolet-B (UV-B) Radiation on Photosynthetic Processes","volume":"137","author":"Kataria","year":"2014","journal-title":"J. Photochem. Photobiol. B Biol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"113004","DOI":"10.1016\/j.jphotobiol.2024.113004","article-title":"The Mechanisms of Photoinhibition and Repair in Plants under High Light Conditions and Interplay with Abiotic Stressors","volume":"259","author":"Didaran","year":"2024","journal-title":"J. Photochem. Photobiol. B Biol."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Lu, D., Zhang, Y., Zhang, A., and Lu, C. (2022). Non-Photochemical Quenching: From Light Perception to Photoprotective Gene Expression. Int. J. Mol. Sci., 23.","DOI":"10.3390\/ijms23020687"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1311","DOI":"10.1104\/pp.17.01143","article-title":"Light Signaling-Dependent Regulation of Photoinhibition and Photoprotection in Tomato","volume":"176","author":"Wang","year":"2018","journal-title":"Plant Physiol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.tplants.2012.09.003","article-title":"UV-B Exposure, ROS, and Stress: Inseparable Companions or Loosely Linked Associates?","volume":"18","author":"Hideg","year":"2013","journal-title":"Trends Plant Sci."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"501","DOI":"10.1111\/j.1399-3054.2012.01656.x","article-title":"UV-B Radiation: From Generic Stressor to Specific Regulator","volume":"145","author":"Jansen","year":"2012","journal-title":"Physiol. Plant."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1763","DOI":"10.1111\/nph.70303","article-title":"UV RESISTANCE LOCUS 8 Signalling Enhances Photosynthetic Resilience to Herbicide-induced Damage in Arabidopsis thaliana","volume":"247","author":"Groves","year":"2025","journal-title":"New Phytol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"407","DOI":"10.1146\/annurev.arplant.59.032607.092953","article-title":"Signal Transduction in Responses to UV-B Radiation","volume":"60","author":"Jenkins","year":"2009","journal-title":"Annu. Rev. Plant Biol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"744","DOI":"10.1104\/pp.112.211375","article-title":"Multiple Roles for UV RESISTANCE LOCUS8 in Regulating Gene Expression and Metabolite Accumulation in Arabidopsis under Solar Ultraviolet Radiation","volume":"161","author":"Morales","year":"2013","journal-title":"Plant Physiol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1975","DOI":"10.1105\/tpc.105.040097","article-title":"CONSTITUTIVELY PHOTOMORPHOGENIC1 Is Required for the UV-B Response in Arabidopsis","volume":"18","author":"Oravecz","year":"2006","journal-title":"Plant Cell"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"584","DOI":"10.1016\/j.tplants.2012.05.004","article-title":"The Photomorphogenic Repressors COP1 and DET1: 20 Years Later","volume":"17","author":"Lau","year":"2012","journal-title":"Trends Plant Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1126\/science.1200660","article-title":"Perception of UV-B by the Arabidopsis UVR8 Protein","volume":"332","author":"Rizzini","year":"2011","journal-title":"Science"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1016\/j.plantsci.2012.07.014","article-title":"Flavonoids as Antioxidants in Plants: Location and Functional Significance","volume":"196","author":"Agati","year":"2012","journal-title":"Plant Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/j.pbi.2018.04.018","article-title":"Photoreceptor-Mediated Regulation of the COP1\/SPA E3 Ubiquitin Ligase","volume":"45","author":"Podolec","year":"2018","journal-title":"Curr. Opin. Plant Biol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1126\/science.aaf9030","article-title":"Photoactivation and Inactivation of Arabidopsis Cryptochrome 2","volume":"354","author":"Wang","year":"2016","journal-title":"Science"},{"key":"ref_33","first-page":"88","article-title":"The Arabidopsis bZIP Transcription Factor HY5 Regulates Expression of the PFG1\/MYB12 Gene in Response to Light and Ultraviolet-B Radiation","volume":"33","author":"Stracke","year":"2010","journal-title":"Plant Cell Environ."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1007\/s42994-021-00038-1","article-title":"Integration of Light and Hormone Signaling Pathways in the Regulation of Plant Shade Avoidance Syndrome","volume":"2","author":"Liu","year":"2021","journal-title":"aBIOTECH"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1104\/pp.107.108456","article-title":"UV-B Signaling Pathways with Different Fluence-Rate Response Profiles Are Distinguished in Mature Arabidopsis Leaf Tissue by Requirement for UVR8, HY5, and HYH","volume":"146","author":"Brown","year":"2008","journal-title":"Plant Physiol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1247","DOI":"10.1111\/nph.15469","article-title":"Signal Transduction Mediated by the Plant UV-B Photoreceptor UVR8","volume":"221","author":"Liang","year":"2019","journal-title":"New Phytol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1093\/plcell\/koac316","article-title":"Brassinosteroids Promote Etiolated Apical Structures in Darkness by Amplifying the Ethylene Response via the EBF-EIN3\/PIF3 Circuit","volume":"35","author":"Wang","year":"2023","journal-title":"Plant Cell"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"773","DOI":"10.1042\/BST20190062","article-title":"Stop CRYing! Inhibition of Cryptochrome Function by Small Proteins","volume":"50","author":"Kruusvee","year":"2022","journal-title":"Biochem. Soc. Trans."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Wang, Y., Wang, W., Jia, Q., Tian, H., Wang, X., Li, Y., Hussain, S., Hussain, H., Wang, T., and Wang, S. (2023). BIC2, a Cryptochrome Function Inhibitor, Is Involved in the Regulation of ABA Responses in Arabidopsis. Plants, 12.","DOI":"10.3390\/plants12112220"},{"key":"ref_40","first-page":"19","article-title":"SPA1: A New Genetic Locus Involved in Phytochrome A\u2013Specific Signal Transduction","volume":"10","author":"Hoecker","year":"1998","journal-title":"Plant Cell"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"2642","DOI":"10.1101\/gad.1122903","article-title":"The COP1\u2013SPA1 Interaction Defines a Critical Step in Phytochrome A-Mediated Regulation of HY5 Activity","volume":"17","author":"Saijo","year":"2003","journal-title":"Genes Dev."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"841","DOI":"10.1016\/j.cub.2011.03.048","article-title":"Blue Light-Dependent Interaction of CRY2 with SPA1 Regulates COP1 Activity and Floral Initiation in Arabidopsis","volume":"21","author":"Zuo","year":"2011","journal-title":"Curr. Biol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1023\/A:1009717226788","article-title":"In Assessing Biological UV-B Effects, Natural Fluctuations of Solar Radiation Should Be Taken into Account","volume":"128","author":"Santas","year":"1997","journal-title":"Plant Ecol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1016\/j.agrformet.2003.08.015","article-title":"Field Crop Responses to Ultraviolet-B Radiation: A Review","volume":"120","author":"Kakani","year":"2003","journal-title":"Agric. For. Meteorol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1016\/0076-6879(87)48036-1","article-title":"[34] Chlorophylls and Carotenoids: Pigments of Photosynthetic Biomembranes","volume":"Volume 148","author":"Lichtenthaler","year":"1987","journal-title":"Methods in Enzymology"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"981","DOI":"10.1111\/j.1365-313X.2006.03021.x","article-title":"PIF3 Regulates Anthocyanin Biosynthesis in an HY5-Dependent Manner with Both Factors Directly Binding Anthocyanin Biosynthetic Gene Promoters in Arabidopsis: Functional Relationship between PIF3 and HY5","volume":"49","author":"Shin","year":"2007","journal-title":"Plant J."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"998","DOI":"10.1038\/s41477-021-00980-4","article-title":"Chlorophyll a Fluorescence Illuminates a Path Connecting Plant Molecular Biology to Earth-System Science","volume":"7","author":"Magney","year":"2021","journal-title":"Nat. Plants"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1007\/s11120-025-01178-x","article-title":"Revisiting the QA Model of Chlorophyll-a Fluorescence Induction: New Perspectives to Monitor the Photochemical Activity and Structural Dynamics of Photosystem II","volume":"163","author":"Garab","year":"2025","journal-title":"Photosynth. Res."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Abramova, A., Vereshchagin, M., Kulkov, L., Kreslavski, V.D., Kuznetsov, V.V., and Pashkovskiy, P. (2023). Potential Role of Phytochromes A and B and Cryptochrome 1 in the Adaptation of Solanum lycopersicum to UV-B Radiation. Int. J. Mol. Sci., 24.","DOI":"10.3390\/ijms241713142"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/5\/2436\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,8]],"date-time":"2026-03-08T05:31:36Z","timestamp":1772947896000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/27\/5\/2436"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,6]]},"references-count":49,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,3]]}},"alternative-id":["ijms27052436"],"URL":"https:\/\/doi.org\/10.3390\/ijms27052436","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,6]]}}}