{"doi":"10.1093/plcell/koad173","title":"Arabidopsis PLANT U-BOX44 down-regulates osmotic stress signaling by mediating Ca2+-DEPENDENT PROTEIN KINASE4 degradation","abstract":"Calcium (Ca2+)-dependent protein kinases (CPKs) are essential regulators of plant responses to diverse environmental stressors, including osmotic stress. CPKs are activated by an increase in intracellular Ca2+ levels triggered by osmotic stress. However, how the levels of active CPK protein are dynamically and precisely regulated has yet to be determined. Here, we demonstrate that NaCl/mannitol-induced osmotic stress promoted the accumulation of CPK4 protein by disrupting its 26S proteasome-mediated CPK4 degradation in Arabidopsis (Arabidopsis thaliana). We isolated PLANT U-BOX44 (PUB44), a U-box type E3 ubiquitin ligase that ubiquitinates CPK4 and triggers its degradation. A calcium-free or kinase-inactive CPK4 variant was preferentially degraded compared to the Ca2+-bound active form of CPK4. Furthermore, PUB44 exhibited a CPK4-dependent negative role in the response of plants to osmotic stress. Osmotic stress induced the accumulation of CPK4 protein by inhibiting PUB44-mediated CPK4 degradation. The present findings reveal a mechanism for regulating CPK protein levels and establish the relevance of PUB44-dependent CPK4 regulation in modulating plant osmotic stress responses, providing insights into osmotic stress signal transduction mechanisms.","journal":"The Plant Cell","year":2023,"id":328654,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":22,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9614,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1050567,"name":"Xiliang Liao","orcid":"0000-0003-0726-8571","position":1,"is_corresponding":false},{"id":1050568,"name":"Yan-Qiu Tan","orcid":"0000-0002-1750-3558","position":2,"is_corresponding":false},{"id":1050569,"name":"Xiruo Wang","orcid":"0009-0006-2425-930X","position":3,"is_corresponding":false},{"id":226500,"name":"Julian I. Schroeder","orcid":"0000-0002-3283-5972","position":4,"is_corresponding":false},{"id":1050570,"name":"Zixing Li","orcid":"0000-0002-2692-9008","position":5,"is_corresponding":false},{"id":413450,"name":"Wei Fan","orcid":"0009-0000-9226-182X","position":0,"is_corresponding":true}],"reference_count":61,"raw_metadata":null,"created_at":"2026-07-19T01:08:56.940647Z","pmid":"37338064","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}