Iron (Fe) deficiency threatens plant growth and health. In response to Fe deficiency, plants reprogram transcription in roots and shoots to maintain Fe homeostasis. However, the molecular mechanism by which Arabidopsis (Arabidopsis thaliana) plants coordinate Fe deficiency responses in the root and shoot remains unclear. Here, we uncover the roles of BRUTUS (BTS), BTS-LIKE1 (BTSL1), and BTSL2, along with the bHLH IVc subgroup proteins (bHLH34, bHLH104, bHLH105, and bHLH115), in orchestrating the Fe deficiency responses of roots and shoots in Arabidopsis. BTS relieves shoot Fe toxicity and regulates Fe deficiency responses of shoots and roots, but BTSL1/2 are only involved in root Fe-deficiency responses. Furthermore, BTSL1/2 share similar molecular functions with BTS to a certain extent, as they also interact with bHLH IVc proteins and promote the degradation of bHLH105 and bHLH115. The simultaneous loss of the four bHLH IVc proteins completely halts the Fe deficiency responses across the whole plant. Moreover, bHLH IVc proteins are essential for BTSL1/2 functions in Fe deficiency responses. Meanwhile, bHLH IVc proteins directly enhance BTSL1/2 expression. This research sheds light on the distinct roles of BTS and BTSL1/2 in the root and shoot and emphasizes crucial roles of bHLH IVc proteins in regulating Fe deficiency responses in the root and shoot.
{"title":"Arabidopsis BRUTUS, BRUTUS-LIKE, and bHLH IVc subgroup proteins coordinate iron homeostasis in the root and shoot.","authors":"Junhui Zhao,Yang Li,Huaqian Ping,Rihua Lei,Bangzhen Pan,Gang Liang","doi":"10.1093/plcell/koag006","DOIUrl":"https://doi.org/10.1093/plcell/koag006","url":null,"abstract":"Iron (Fe) deficiency threatens plant growth and health. In response to Fe deficiency, plants reprogram transcription in roots and shoots to maintain Fe homeostasis. However, the molecular mechanism by which Arabidopsis (Arabidopsis thaliana) plants coordinate Fe deficiency responses in the root and shoot remains unclear. Here, we uncover the roles of BRUTUS (BTS), BTS-LIKE1 (BTSL1), and BTSL2, along with the bHLH IVc subgroup proteins (bHLH34, bHLH104, bHLH105, and bHLH115), in orchestrating the Fe deficiency responses of roots and shoots in Arabidopsis. BTS relieves shoot Fe toxicity and regulates Fe deficiency responses of shoots and roots, but BTSL1/2 are only involved in root Fe-deficiency responses. Furthermore, BTSL1/2 share similar molecular functions with BTS to a certain extent, as they also interact with bHLH IVc proteins and promote the degradation of bHLH105 and bHLH115. The simultaneous loss of the four bHLH IVc proteins completely halts the Fe deficiency responses across the whole plant. Moreover, bHLH IVc proteins are essential for BTSL1/2 functions in Fe deficiency responses. Meanwhile, bHLH IVc proteins directly enhance BTSL1/2 expression. This research sheds light on the distinct roles of BTS and BTSL1/2 in the root and shoot and emphasizes crucial roles of bHLH IVc proteins in regulating Fe deficiency responses in the root and shoot.","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145986353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polycomb Repressive Complex 2 (PRC2) is a conserved multi-protein complex that catalyzes histone H3 trimethylation at lysine 27 (H3K27me3), an epigenetic mark associated with transcriptional repression. However, the mechanistic link between PRC2-mediated H3K27me3 and light-regulated hypocotyl elongation during photomorphogenesis remains largely unexplored. In this study, we identify the MULTICOPY SUPPRESSOR OF IRA1 (MSI1), a core component of PRC2, as a negative regulator of hypocotyl elongation under light conditions in Arabidopsis thaliana. MSI1 physically interacts with ELONGATED HYPOCOTYL 5 (HY5), a basic leucine zipper (bZIP) transcription factor central to photomorphogenic signaling, in vitro and in vivo. Genetic and molecular analyses reveal that MSI1 is indispensable for HY5-mediated repression of hypocotyl growth, suggesting a cooperative function between chromatin-based silencing and transcriptional regulation. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) showed that MSI1 and HY5 co-occupy numerous genomic loci. HY5 facilitates PRC2 complex recruitment to the target genes by interacting with MSI1, thereby promoting H3K27me3 deposition and repressing gene expression. Furthermore, transcriptomic profiling reveals that MSI1 and HY5 jointly suppress a subset of genes involved in auxin signaling, providing mechanistic insight into their role in photomorphogenesis. Together, our findings uncover an epigenetic mechanism by which HY5 recruits PRC2 through MSI1 to modulate light-responsive growth.
{"title":"The Arabidopsis PRC2 subunit MSI1 interacts with HY5 to repress hypocotyl elongation through H3K27 tri-methylation.","authors":"Yingchao Xu,Min Wang,Mei-Hui Yu,Yan Liu,Wen-Chi Liao,Tao Li,Fu-Yu Hung,Sujuan Gao,Dasen Xie,Keqiang Wu,Songguang Yang","doi":"10.1093/plcell/koag003","DOIUrl":"https://doi.org/10.1093/plcell/koag003","url":null,"abstract":"Polycomb Repressive Complex 2 (PRC2) is a conserved multi-protein complex that catalyzes histone H3 trimethylation at lysine 27 (H3K27me3), an epigenetic mark associated with transcriptional repression. However, the mechanistic link between PRC2-mediated H3K27me3 and light-regulated hypocotyl elongation during photomorphogenesis remains largely unexplored. In this study, we identify the MULTICOPY SUPPRESSOR OF IRA1 (MSI1), a core component of PRC2, as a negative regulator of hypocotyl elongation under light conditions in Arabidopsis thaliana. MSI1 physically interacts with ELONGATED HYPOCOTYL 5 (HY5), a basic leucine zipper (bZIP) transcription factor central to photomorphogenic signaling, in vitro and in vivo. Genetic and molecular analyses reveal that MSI1 is indispensable for HY5-mediated repression of hypocotyl growth, suggesting a cooperative function between chromatin-based silencing and transcriptional regulation. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) showed that MSI1 and HY5 co-occupy numerous genomic loci. HY5 facilitates PRC2 complex recruitment to the target genes by interacting with MSI1, thereby promoting H3K27me3 deposition and repressing gene expression. Furthermore, transcriptomic profiling reveals that MSI1 and HY5 jointly suppress a subset of genes involved in auxin signaling, providing mechanistic insight into their role in photomorphogenesis. Together, our findings uncover an epigenetic mechanism by which HY5 recruits PRC2 through MSI1 to modulate light-responsive growth.","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145937720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G-protein pathways play critical roles in many aspects of plant development. Among the five Gγ proteins in rice (Oryza sativa), DENSE AND ERECT PANICLE 1 (DEP1) and GRAIN SIZE 3 (GS3) have been shown to determine grain size, but the exact mechanism by which G proteins regulate the process is not fully understood. Here we demonstrate that the G proteins modulate the stability of MPS ONE BINDER KINASE ACTIVATOR-LIKE 1A (OsMOB1A), a core component in the Hippo pathway. In the Hippo signaling pathway, the protein kinase Serine/Threonine Kinase 1 (OsSIK1) phosphorylates the scaffold protein OsMOB1A and thus regulates its stability. We discovered that disruption of either OsSIK1 or OsMOB1A leads to smaller grains, whereas overexpression of either gene results in larger grains. DEP1 and GS3 physically interact with OsSIK1, thus affecting the OsSIK1-OsMOB1A interaction and the phosphorylation of OsMOB1A by OsSIK1. OsMOB1A stability was decreased in vivo in dep1-1 mutant and GS3 overexpression lines, but increased in gs3 mutants and DEP1 overexpression lines. Moreover, the impact of Gγ proteins on the Hippo pathway was Gγ dose-dependent. Genetic analysis indicated that Gγ proteins act upstream of the Hippo pathway. Our results uncovered a molecular mechanism by which G proteins regulate rice grain size by modulating the Hippo signaling pathway and provide potential targets for improving grain yield.
{"title":"G proteins regulate rice grain size by modulating the Hippo signaling pathway","authors":"Fangfang Zhou, Zhiai Guo, Yanxia Ling, Youfa Cheng","doi":"10.1093/plcell/koaf288","DOIUrl":"https://doi.org/10.1093/plcell/koaf288","url":null,"abstract":"G-protein pathways play critical roles in many aspects of plant development. Among the five Gγ proteins in rice (Oryza sativa), DENSE AND ERECT PANICLE 1 (DEP1) and GRAIN SIZE 3 (GS3) have been shown to determine grain size, but the exact mechanism by which G proteins regulate the process is not fully understood. Here we demonstrate that the G proteins modulate the stability of MPS ONE BINDER KINASE ACTIVATOR-LIKE 1A (OsMOB1A), a core component in the Hippo pathway. In the Hippo signaling pathway, the protein kinase Serine/Threonine Kinase 1 (OsSIK1) phosphorylates the scaffold protein OsMOB1A and thus regulates its stability. We discovered that disruption of either OsSIK1 or OsMOB1A leads to smaller grains, whereas overexpression of either gene results in larger grains. DEP1 and GS3 physically interact with OsSIK1, thus affecting the OsSIK1-OsMOB1A interaction and the phosphorylation of OsMOB1A by OsSIK1. OsMOB1A stability was decreased in vivo in dep1-1 mutant and GS3 overexpression lines, but increased in gs3 mutants and DEP1 overexpression lines. Moreover, the impact of Gγ proteins on the Hippo pathway was Gγ dose-dependent. Genetic analysis indicated that Gγ proteins act upstream of the Hippo pathway. Our results uncovered a molecular mechanism by which G proteins regulate rice grain size by modulating the Hippo signaling pathway and provide potential targets for improving grain yield.","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"118 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Frost fighters: The discovery of a tripartite molecular module that confers cold stress tolerance in apple.","authors":"Margot Raffeiner","doi":"10.1093/plcell/koaf287","DOIUrl":"https://doi.org/10.1093/plcell/koaf287","url":null,"abstract":"","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Hidden Gradients Before Form: A Spatial Transcriptomic Atlas of Wheat Spike Patterning.","authors":"Min-Yao Jhu,Travis A Lee","doi":"10.1093/plcell/koaf286","DOIUrl":"https://doi.org/10.1093/plcell/koaf286","url":null,"abstract":"","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145777422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MYB30-Interacting E3 Ligase1 (MdMIEL1) plays a negative role in apple (Malus × domestica) cold tolerance by mediating the degradation of its target proteins. Its protein stability decreases under cold stress; however, how MdMIEL1 is regulated under cold conditions remains unclear. Here, we report that the α-catalytic subunit of sucrose non-fermenting-1-related protein kinase, MdKIN10, a positive regulator of cold stress, interacts with MdMIEL1, leading to its phosphorylation and subsequent degradation. Specifically, cold-activated MdKIN10 phosphorylates MdMIEL1 at serine 198, which occurs near the AIM motif; this modification further enhances the interaction between MdMIEL1 and MdATG8i, thereby promoting MdMIEL1 degradation through the autophagy pathway. Furthermore, MdBBX7, which functions as a positive regulator in apple cold stress responses by positively regulating the expression of ω-3 fatty acid desaturase (MdFAD8) and C-repeat-binding factor 2 (MdCBF2), thus promoting fatty acid desaturation and cold-responsive gene expression, is a target of MdMIEL1. In addition, MdKIN10-mediated phosphorylation of MdMIEL1 at Ser198 attenuates the ability of MdMIEL1 to inhibit apple cold tolerance and decrease MdBBX7 protein abundance in response to cold stress. Our study reveals an intricate post-translational modification cascade of MdKIN10-MdMIEL1-MdBBX7 molecular module under cold stress in apple.
{"title":"MdKIN10-mediated phosphorylation of the E3 ubiquitin ligase MdMIEL1 leads to its autophagic degradation under cold stress","authors":"Fang Zhi, Tianle Fan, Yutian Zhang, Pengxiang Chen, Shuangcheng He, Xuewei Li, Shuo Zhang, Jieqiang He, Xiaoxia Shen, Chana Bao, Chundong Niu, Fengwang Ma, Yinpeng Xie, Qingmei Guan","doi":"10.1093/plcell/koaf284","DOIUrl":"https://doi.org/10.1093/plcell/koaf284","url":null,"abstract":"MYB30-Interacting E3 Ligase1 (MdMIEL1) plays a negative role in apple (Malus × domestica) cold tolerance by mediating the degradation of its target proteins. Its protein stability decreases under cold stress; however, how MdMIEL1 is regulated under cold conditions remains unclear. Here, we report that the α-catalytic subunit of sucrose non-fermenting-1-related protein kinase, MdKIN10, a positive regulator of cold stress, interacts with MdMIEL1, leading to its phosphorylation and subsequent degradation. Specifically, cold-activated MdKIN10 phosphorylates MdMIEL1 at serine 198, which occurs near the AIM motif; this modification further enhances the interaction between MdMIEL1 and MdATG8i, thereby promoting MdMIEL1 degradation through the autophagy pathway. Furthermore, MdBBX7, which functions as a positive regulator in apple cold stress responses by positively regulating the expression of ω-3 fatty acid desaturase (MdFAD8) and C-repeat-binding factor 2 (MdCBF2), thus promoting fatty acid desaturation and cold-responsive gene expression, is a target of MdMIEL1. In addition, MdKIN10-mediated phosphorylation of MdMIEL1 at Ser198 attenuates the ability of MdMIEL1 to inhibit apple cold tolerance and decrease MdBBX7 protein abundance in response to cold stress. Our study reveals an intricate post-translational modification cascade of MdKIN10-MdMIEL1-MdBBX7 molecular module under cold stress in apple.","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"268 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Plants deploy sophisticated mechanisms to fine-tune plant immunity, as constitutive activation of disease resistance is detrimental. The Arabidopsis (Arabidopsis thaliana) Raf-like kinase ENHANCED DISEASE RESISTANCE 1 (EDR1) negatively regulates defense responses; however, how EDR1 functions and its phosphorylation substrates remain elusive. Here, we show that EDR1 interacts with and phosphorylates the transcription factor MYC2 at T353/T357. MYC2 positively regulates powdery mildew resistance, and the phosphorylation of MYC2 at T353/T357 by EDR1 inhibits its ability to bind to DNA and subsequently suppresses its function in powdery mildew resistance. MYC2 is dephosphorylated by protein phosphatase 2A (PP2A) Bɑ at T353/T357, which releases EDR1-mediated inhibition during infection to promote transcription and resistance. PP2A Bɑ is activated by MITOGEN-ACTIVATED KINASE 15 (MPK15), a positive regulator of powdery mildew resistance. Consistently, the pp2a bɑ mutant displays EDR1-dependent susceptibility to powdery mildew. Taken together, these results show that the activation of MYC2 is dynamically modulated by EDR1 and PP2A Bɑ in plant immunity. These findings not only expand our understanding of the roles of EDR1 and MYC2 but also reveal a mechanism by which plants fine-tune MYC2-mediated powdery mildew resistance via a dynamic phosphorylation regulatory module.
植物部署复杂的机制来微调植物免疫，因为抗病性的组成激活是有害的。拟南芥（Arabidopsis thaliana） Raf-like kinase ENHANCED DISEASE RESISTANCE 1 （EDR1）负向调控防御反应；然而，EDR1的功能及其磷酸化底物仍然是一个谜。在这里，我们发现EDR1与转录因子MYC2在T353/T357位点相互作用并磷酸化。MYC2正向调节白粉病抗性，EDR1磷酸化MYC2的T353/T357位点抑制其与DNA结合的能力，进而抑制其在白粉病抗性中的功能。MYC2在T353/T357位点被蛋白磷酸酶2A (PP2A) B β去磷酸化，在感染期间释放edr1介导的抑制，促进转录和抗性。PP2A B æ被丝裂原活化激酶15 （MPK15）激活，MPK15是白粉病抗性的正调节因子。一致地，pp2a b突变体对白粉病表现出edr1依赖性易感性。综上所述，这些结果表明，在植物免疫中，MYC2的激活是由EDR1和PP2A B]动态调节的。这些发现不仅扩大了我们对EDR1和MYC2作用的理解，而且揭示了植物通过动态磷酸化调控模块微调MYC2介导的白粉病抗性的机制。
{"title":"The EDR1-PP2A phospho-regulatory module fine-tunes MYC2-mediated plant disease resistance.","authors":"Guitao Zhong,Jing Shao,Zhanchun Wang,Qiuru Lin,Yongming Chen,Renjie Chen,Hua Shi,Chunzhao Zhao,Dingzhong Tang,Wei Wang","doi":"10.1093/plcell/koaf285","DOIUrl":"https://doi.org/10.1093/plcell/koaf285","url":null,"abstract":"Plants deploy sophisticated mechanisms to fine-tune plant immunity, as constitutive activation of disease resistance is detrimental. The Arabidopsis (Arabidopsis thaliana) Raf-like kinase ENHANCED DISEASE RESISTANCE 1 (EDR1) negatively regulates defense responses; however, how EDR1 functions and its phosphorylation substrates remain elusive. Here, we show that EDR1 interacts with and phosphorylates the transcription factor MYC2 at T353/T357. MYC2 positively regulates powdery mildew resistance, and the phosphorylation of MYC2 at T353/T357 by EDR1 inhibits its ability to bind to DNA and subsequently suppresses its function in powdery mildew resistance. MYC2 is dephosphorylated by protein phosphatase 2A (PP2A) Bɑ at T353/T357, which releases EDR1-mediated inhibition during infection to promote transcription and resistance. PP2A Bɑ is activated by MITOGEN-ACTIVATED KINASE 15 (MPK15), a positive regulator of powdery mildew resistance. Consistently, the pp2a bɑ mutant displays EDR1-dependent susceptibility to powdery mildew. Taken together, these results show that the activation of MYC2 is dynamically modulated by EDR1 and PP2A Bɑ in plant immunity. These findings not only expand our understanding of the roles of EDR1 and MYC2 but also reveal a mechanism by which plants fine-tune MYC2-mediated powdery mildew resistance via a dynamic phosphorylation regulatory module.","PeriodicalId":501012,"journal":{"name":"The Plant Cell","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145777300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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