The Experts below are selected from a list of 12156 Experts worldwide ranked by ideXlab platform
Hongwei Guo - One of the best experts on this subject based on the ideXlab platform.
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the ring e3 ligase sdir1 destabilizes EBF1 ebf2 and modulates the ethylene response to ambient temperature fluctuations in arabidopsis
Proceedings of the National Academy of Sciences of the United States of America, 2021Co-Authors: Lian Jin, Dongdong Hao, Xing Wen, Qi Xie, Hongwei GuoAbstract:The gaseous phytohormone ethylene mediates numerous aspects of plant growth and development as well as stress responses. The F-box proteins EIN3-binding F-box protein 1 (EBF1) and EBF2 are key components that ubiquitinate and degrade the master transcription factors ethylene insensitive 3 (EIN3) and EIN3-like 1 (EIL1) in the ethylene response pathway. Notably, EBF1 and EBF2 themselves undergo the 26S proteasome-mediated proteolysis induced by ethylene and other stress signals. However, despite their importance, little is known about the mechanisms regulating the degradation of these proteins. Here, we show that a really interesting new gene (RING)-type E3 ligase, salt- and drought-induced ring finger 1 (SDIR1), positively regulates the ethylene response and promotes the accumulation of EIN3. Further analyses indicate that SDIR1 directly interacts with EBF1/EBF2 and targets them for ubiquitination and proteasome-dependent degradation. We show that SDIR1 is required for the fine tuning of the ethylene response to ambient temperature changes by mediating temperature-induced EBF1/EBF2 degradation and EIN3 accumulation. Thus, our work demonstrates that SDIR1 functions as an important modulator of ethylene signaling in response to ambient temperature changes, thereby enabling plant adaptation under fluctuating environmental conditions.
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ethylene induced stabilization of ethylene insensitive3 and ein3 like1 is mediated by proteasomal degradation of ein3 binding f box 1 and 2 that requires ein2 in arabidopsis
The Plant Cell, 2010Co-Authors: Qiong Zhao, Joseph R Ecker, Zhiqiang Jiang, Chen Zhang, Ying Han, Yidong Liu, Shuqun Zhang, Hongwei GuoAbstract:Plant responses to ethylene are mediated by regulation of EBF1/2-dependent degradation of the ETHYLENE INSENSITIVE3 (EIN3) transcription factor. Here, we report that the level of EIL1 protein is upregulated by ethylene through an EBF1/2-dependent pathway. Genetic analysis revealed that EIL1 and EIN3 cooperatively but differentially regulate a wide array of ethylene responses, with EIL1 mainly inhibiting leaf expansion and stem elongation in adult plants and EIN3 largely regulating a multitude of ethylene responses in seedlings. When EBF1 and EBF2 are disrupted, EIL1 and EIN3 constitutively accumulate in the nucleus and remain unresponsive to exogenous ethylene application. Further study revealed that the levels of EBF1 and EBF2 proteins are downregulated by ethylene and upregulated by silver ion and MG132, suggesting that ethylene stabilizes EIN3/EIL1 by promoting EBF1 and EBF2 proteasomal degradation. Also, we found that EIN2 is indispensable for mediating ethylene-induced EIN3/EIL1 accumulation and EBF1/2 degradation, whereas MKK9 is not required for ethylene signal transduction, contrary to a previous report. Together, our studies demonstrate that ethylene similarly regulates EIN3 and EIL1, the two master transcription factors coordinating myriad ethylene responses, and clarify that EIN2 but not MKK9 is required for ethylene-induced EIN3/EIL1 stabilization. Our results also reveal that EBF1 and EBF2 act as essential ethylene signal transducers that by themselves are subject to proteasomal degradation.
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genetic basis of ethylene perception and signal transduction in arabidopsis
Journal of Integrative Plant Biology, 2008Co-Authors: Ziqiang Zhu, Hongwei GuoAbstract:Ethylene is a simple gaseous hormone in plants. It plays important roles in plant development and stress tolerance. In the presence of ethylene treatment, all ethylene receptors are in an activated form, which can physically interact with CTR1 and consequently recruit CTR1 protein to endoplasmic reticulum membraneto activate it. Activated CTR1 suppresses the downstream signal transduction by an unknown mechanism. Upon binding to its receptors, ethylene will inactivate the receptor/CTR1 module and in turn alleviate their inhibitory effect on two positive regulators acting downstream of CTR1: EIN2 and EIN3. Genetic study reveals that EIN2 is an essential component in the ethylene signaling pathway but its biochemical function remains a mystery. EIN3 is a plant-specific transcription factor and its protein abundance in the nucleus is rapidly induced upon ethylene treatment. In the absence of ethylene signal, EIN3 protein is degraded by an SCF complex containing one of the two F-box proteins EBF1/EBF2 in a 26S proteasome-dependent manner. EIN3 can bind to the promoter sequences of a number of downstream components, such as ERFs, which in turn bind to a GCC box, a cis-element found in many ethylene-regulated defense genes. Ethylene has been shown to also regulate many other hormones' signaling pathways including auxin, abscisic acid and jasmonic acid, implying the existence of complicated signaling networks in the growth, development and defense responses of various plants.
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ethylene insensitive5 encodes a 5 3 exoribonuclease required for regulation of the ein3 targeting f box proteins EBF1 2
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Gabriela Olmedo, Hongwei Guo, Brian D Gregory, Saeid Nourizadeh, Laura Aguilarhenonin, Plinio Guzman, Joseph R EckerAbstract:Ethylene is a gaseous plant growth regulator that controls a multitude of developmental and stress responses. Recently, the levels of Arabidopsis EIN3 protein, a key transcription factor mediating ethylene-regulated gene expression, have been demonstrated to increase in response to the presence of ethylene gas. Furthermore, in the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F-box proteins, EBF1 and EBF2. Here we report the identification of ETHYLENE-INSENSITIVE5 as the 5′→3′ exoribonuclease XRN4. Specifically, we demonstrate that EIN5 is a component of the ethylene signal transduction cascade acting downstream of CTR1 that is required for ethylene-mediated gene expression changes. Furthermore, we find that the ethylene insensitivity of ein5 mutant plants is a consequence of the over-accumulation of EBF1 and EBF2 mRNAs resulting in the under-accumulation of EIN3 even in the presence of ethylene gas. Together, our results suggest that the role of EIN5 in ethylene perception is to antagonize the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay, which consequently allows the accumulation of EIN3 protein to trigger the ethylene response.
Mikael Sigvardsson - One of the best experts on this subject based on the ideXlab platform.
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combined heterozygous loss of EBF1 and pax5 allows for t lineage conversion of b cell progenitors
Journal of Experimental Medicine, 2015Co-Authors: Jonas Ungerback, Josefine Ahsberg, Rajesh Somasundaram, Tobias Strid, Mikael SigvardssonAbstract:To investigate how transcription factor levels impact B-lymphocyte development, we generated mice carrying transheterozygous mutations in the Pax5 and EBF1 genes. Whereas combined reduction of Pax5 and EBF1 had minimal impact on the development of the earliest CD19+ progenitors, these cells displayed an increased T cell potential in vivo and in vitro. The alteration in lineage fate depended on a Notch1-mediated conversion process, whereas no signs of de-differentiation could be detected. The differences in functional response to Notch signaling in Wt and Pax5+/−EBF1+/− pro–B cells were reflected in the transcriptional response. Both genotypes responded by the generation of intracellular Notch1 and activation of a set of target genes, but only the Pax5+/−EBF1+/− pro–B cells down-regulated genes central for the preservation of stable B cell identity. This report stresses the importance of the levels of transcription factor expression during lymphocyte development, and suggests that Pax5 and EBF1 collaborate to modulate the transcriptional response to Notch signaling. This provides an insight on how transcription factors like EBF1 and Pax5 preserve cellular identity during differentiation.
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early b cell factor 1 regulates the expansion of b cell progenitors in a dose dependent manner
Journal of Biological Chemistry, 2013Co-Authors: Josefine Ahsberg, Jonas Ungerback, Tobias Strid, Malin Larsson, Eva Welinder, Jenny Stjernberg, Hong Qian, Mikael SigvardssonAbstract:Transcription factor doses are of importance for normal and malignant B-lymphocyte development; however, the understanding of underlying mechanisms and functional consequences of reduced transcription factor levels is limited. We have analyzed progenitor and B-lineage compartments in mice carrying heterozygote mutations in the E2a, EBF1, or Pax5 gene. Although lymphoid progenitors from EBF1 or Pax5 heterozygote mice were specified and lineage-restricted in a manner comparable with Wt progenitors, this process was severely impaired in E2a heterozygote mutant mice. This defect was not significantly enhanced upon combined deletion of E2a with EBF1 or Pax5. Analysis of the pre-B-cell compartment in EBF1 heterozygote mice revealed a reduction in cell numbers. These cells expressed Pax5 and other B-lineage-associated genes, and global gene expression analysis suggested that the reduction of the pre-B-cell compartment was a result of impaired pre-B-cell expansion. This idea was supported by a reduction in IL2Rα-expressing late pre-B-cells as well as by cell cycle analysis and by the finding that the complexity of the VDJ rearrangement patterns was comparable in Wt and EBF1+/− pre-B-cells, although the number of progenitors was reduced. Heterozygote deletion of EBF1 resulted in impaired response to IL7 in vitro and reduced expression levels of pre-BCR on the cell surface, providing possible explanations for the observed stage-specific reduction in cellular expansion. Thus, transcription factor doses are critical for specification as well as expansion of B-lymphoid progenitors, providing increased insight into the molecular regulation of B-cell development.
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positive intergenic feedback circuitry involving EBF1 and foxo1 orchestrates b cell fate
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Robert Mansson, Mikael Sigvardsson, Josefine Ahsberg, Eva Welinder, Yin C Lin, Christopher Benner, Christopher K Glass, Joseph S Lucas, Cornelis MurreAbstract:Recent studies have identified a number of transcriptional regulators, including E2A, early B-cell factor 1 (EBF1), FOXO1, and paired box gene 5 (PAX5), that promote early B-cell development. However, how this ensemble of regulators mechanistically promotes B-cell fate remains poorly understood. Here we demonstrate that B-cell development in FOXO1-deficient mice is arrested in the common lymphoid progenitor (CLP) LY6D(+) cell stage. We demonstrate that this phenotype closely resembles the arrest in B-cell development observed in EBF1-deficient mice. Consistent with these observations, we find that the transcription signatures of FOXO1- and EBF1-deficient LY6D(+) progenitors are strikingly similar, indicating a common set of target genes. Furthermore, we found that depletion of EBF1 expression in LY6D(+) CLPs severely affects FOXO1 mRNA abundance, whereas depletion of FOXO1 activity in LY6D(+) CLPs ablates EBF1 transcript levels. We generated a global regulatory network from EBF1 and FOXO1 genome-wide transcription factor occupancy and transcription signatures derived from EBF1- and FOXO1-deficient CLPs. This analysis reveals that EBF1 and FOXO1 act in a positive feedback circuitry to promote and stabilize specification to the B-cell lineage.
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a dose dependent role for EBF1 in repressing non b cell specific genes
European Journal of Immunology, 2011Co-Authors: Kara Lukin, Mikael Sigvardsson, Robert Mansson, Scott Fields, Lisa Guerrettaz, Desiree Straign, Valerie Rodriguez, Sasan Zandi, John C CambierAbstract:In the absence of early B-cell factor 1 (EBF1), B-cell development is arrested at an uncommitted progenitor stage that exhibits increased lineage potentials. Previously, we investigated the roles of EBF1 and its DNA-binding partner Runx1 by evaluating B lymphopoiesis in single (EBF1(het) and Runx1(het)) and compound haploinsufficent (EBF1(+/-) Runx1(+/-), ER(het)) mice. Here, we demonstrate that decreased EBF1 gene dosage results in the inappropriate expression of NK-cell lineage-specific genes in B-cell progenitors. Moreover, prolonged expression of Ly6a/Sca-1 suggested the maintenance of a relatively undifferentiated phenotype. These effects were exacerbated by reduced expression of Runx1 and occurred despite expression of Pax5. Repression of inappropriately expressed genes was restored in most pre-B and all immature B cells of ER(het) mice. Enforced EBF1 expression repressed promiscuous transcription in pro-B cells of ER(het) mice and in EBF1(-/-) Pax5(-/-) fetal liver cells. Together, our studies suggest that normal levels of EBF1 are critical for maintaining B-cell identity by directing repression of non-B-cell-specific genes.
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temporal and sequential expression of EBF1 and pax5 restricts the non b cell fate in early lymphopoiesis
Blood, 2010Co-Authors: Sasan Zandi, Robert Mansson, Panagiotis Tsapogas, Jenny Zetterblad, Mikael SigvardssonAbstract:Abstract 3867 The generation of B cells from multipotent hematopoietic stem cells involves activation of B cell specific and repression of alternative lineage programs. This process to a large extent is under the control of transcription factors such as EBF1, E2A, IKAROS and PAX5. Inactivation of PAX5 and EBF1, by point mutations or deletions can be found in 30% of the acute lymphocytic leukemia (ALL) cases, probably due to a disturbance of differentiation in early B cell development. Conditional deletion of PAX5 and EBF1 leads to a complete block in B cell production and subsequent accumulation of early immature B cell progenitors. Although the roles of these transcription factors have been established in B cell development, the presence of a feedback loop between PAX5 and EBF1 as well as lack of well defined early B cell developmental events and cell populations, lead to some discrepancies in the current literature regarding the role of these factors in restricting non-B cell lineages and the establishment of B cell fate. By using a combination of RAG1/EBF1 reporter mice and newly identified surface markers i.e Ly6D, we have shown the exact point of myeloid (M), natural killer (NK) and T cells restriction within conventional common lymphoid progenitors (CLP) population. The Lin-IL7r+flt3+kit lo Sca1 lo (CLP)Ly6D-λ5- population retains the residue of myeloid potential together with dendritic (D), Nk, T and B potentials. Upon expression of Ly6D, these cells lose the residual myeloid, NK and D potentials, and eventually the expression of λ5, associated with loss of T cell potential, marks the B-cell committed cells. Based on this new model of lymphoid development we have revisited the functional roles of EBF1 and PAX5 in B-cell commitment. This work suggests that EBF1 restricts the myeloid, NK and D potentials in the transition from CLPLy6D- to CLPLy6D+ stage while the expression of PAX5 in the transition from CLPLy6D+λ5- to CLPLy6D+λ5+ restricts the T cell potential by possibly by counteracting Notch1 signaling in the bone marrow. Considering the high prevalence of PAX5 and EBF1 mutations in ALL and diffuse large B cell lymphoma (DLBL) cases and the fact that inactivation of PAX5 and EBF1 leads to accumulation of B cell progenitors in mice models, understanding the temporal and spatial expression of EBF1 and PAX5 in regard to restriction of non-B cell fates in early stages of lymphoid development will allow us to identify the leukemia-initiating cells and the mechanisms of leukemogenesis in these diseases. Disclosures: No relevant conflicts of interest to declare.
Rudolf Grosschedl - One of the best experts on this subject based on the ideXlab platform.
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3101 EBF1 contributes to the self renewal capacity and lineage differentiation of hspcs
Experimental Hematology, 2020Co-Authors: Aurelie Lenaerts, Pierre Cauchy, Marta Derecka, Rudolf GrosschedlAbstract:Hematopoietic stem cells (HSCs) continually decide to either self-renew or differentiate. In this study we explore the role of lineage-specific transcription factors in HSC cell fate decisions, in particular Early B cell Factor 1 (EBF1) which orchestrates the B cell lineage program and is essential for B cell differentiation. Here, we use EBF1flox/floxTie2Cre (EBF1KO) mice to examine its potential role in hematopoietic stem and progenitor cells (HSPCs). We find that EBF1KO mice display an increased number of HSCs that are less quiescent. Upon chronic 5-fluorouracil treatment, EBF1KO mice show reduced survival as compared to wild type (WT) mice, suggesting that EBF1 helps to maintain HSC quiescence. Additionally, competitive adoptive transfers of EBF1KO HSCs into irradiated WT mice show a decrease in chimerism in both primary and secondary recipients compared to WT HSCs, indicating that EBF1 is required for HSC self-renewal capacity. EBF1KO mice also reveal a significant expansion of myeloid-biased (CD41+) HSCs, myeloid-biased multipotent progenitors (MPP2/3) and mature myeloid cells. B cell-deficient IgM-/- mice do not show an increase in HSC number, loss of quiescence nor loss of chimerism in adoptive transfer experiments, therefore the observed phenotypes in EBF1KO mice are specific to EBF1 and a secondary effect of the loss of B cells. Additionally, we find that EBF1KO HSPCs are not marked by DJ recombination demonstrating that the phenotypes of EBF1 KO mice are not due to the dedifferentiation of B cells. These data indicate that the loss of EBF1 in HSPCs results in a myeloid-biased output and that EBF1 has an unexpected additional function in the regulation of HSC self-renewal and differentiation.
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dynamic EBF1 occupancy directs sequential epigenetic and transcriptional events in b cell programming
Genes & Development, 2018Co-Authors: Pierre Cauchy, Senthilkumar Ramamoorthy, Soren Boller, Lukas Chavez, Rudolf GrosschedlAbstract:B-cell fate determination requires the action of transcription factors that operate in a regulatory network to activate B-lineage genes and repress lineage-inappropriate genes. However, the dynamics and hierarchy of events in B-cell programming remain obscure. To uncouple the dynamics of transcription factor expression from functional consequences, we generated induction systems in developmentally arrested EBF1-/- pre-pro-B cells to allow precise experimental control of EBF1 expression in the genomic context of progenitor cells. Consistent with the described role of EBF1 as a pioneer transcription factor, we show in a time-resolved analysis that EBF1 occupancy coincides with EBF1 expression and precedes the formation of chromatin accessibility. We observed dynamic patterns of EBF1 target gene expression and sequential up-regulation of transcription factors that expand the regulatory network at the pro-B-cell stage. A continuous EBF1 function was found to be required for Cd79a promoter activity and for the maintenance of an accessible chromatin domain that is permissive for binding of other transcription factors. Notably, transient EBF1 occupancy was detected at lineage-inappropriate genes prior to their silencing in pro-B cells. Thus, persistent and transient functions of EBF1 allow for an ordered sequence of epigenetic and transcriptional events in B-cell programming.
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comprehensive proteomic investigation of EBF1 heterozygosity in pro b lymphocytes utilizing data independent acquisition
Journal of Proteome Research, 2018Co-Authors: Yaarub Musa, Rudolf Grosschedl, Soeren Boller, Monika Puchalska, Gerhard MittlerAbstract:Early B cell factor 1 (EBF1) is one of the key transcription factors required for orchestrating B-cell lineage development. Although studies have shown that EBF1 haploinsufficiency is involved in the development of leukemia, no study has been conducted that characterizes the global effect of EBF1 heterozygosity on the proteome of pro-B lymphocytes. Here, we employ both data independent acquisition (DIA) and shotgun data dependent acquisition (DDA) workflows for profiling proteins that are differently expressed between EBF1+/+ and EBF1+/- cells. Both DDA and DIA were able to reveal the downregulation of the EBF1 transcription factor in EBF1+/- pro-B lymphocytes. Further examination of differentially expressed proteins by DIA revealed that, similar to EBF1, the expression of other B-cell lineage regulators, such as TCF3 and Pax5, is also downregulated in EBF1 heterozygous cells. Functional DIA analysis of differentially expressed proteins showed that EBF1 heterozygosity resulted in the deregulation of at le...
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interaction of ccr4 not with EBF1 regulates gene specific transcription and mrna stability in b lymphopoiesis
Genes & Development, 2016Co-Authors: Chengyuan Yang, Senthilkumar Ramamoorthy, Soren Boller, Gerhard Mittler, Marc Rosenbaum, Alfonso Rodriguez Gil, Yumiko Imai, Keiji Kuba, Rudolf GrosschedlAbstract:Transcription factor EBF1 (early B-cell factor 1) regulates early B-cell differentiation by poising or activating lineage-specific genes and repressing genes associated with alternative cell fates. To identify proteins that regulate the diverse functions of EBF1, we used SILAC (stable isotope labeling by amino acids in cell culture)-based mass spectrometry of proteins associated with endogenous EBF1 in pro-B cells. This analysis identified most components of the multifunctional CCR4-NOT complex, which regulates transcription and mRNA degradation. CNOT3 interacts with EBF1, and we identified histidine 240 in EBF1 as a critical residue for this interaction. Complementation of EBF1-/- progenitors with EBF1H240A revealed a partial block of pro-B-cell differentiation and altered expression of specific EBF1 target genes that show either reduced transcription or increased mRNA stability. Most deregulated EBF1 target genes show normal occupancy by EBF1H240A, but we also detected genes with altered occupancy, suggesting that the CCR4-NOT complex affects multiple activities of EBF1. Mice with conditional Cnot3 inactivation recapitulate the block of early B-cell differentiation, which we found to be associated with an impaired autoregulation of EBF1 and reduced expression of pre-B-cell receptor components. Thus, the interaction of the CCR4-NOT complex with EBF1 diversifies the function of EBF1 in a context-dependent manner and may coordinate transcriptional and post-transcriptional gene regulation.
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pioneering activity of the c terminal domain of EBF1 shapes the chromatin landscape for b cell programming
Immunity, 2016Co-Authors: Soren Boller, Senthilkumar Ramamoorthy, Robert Nechanitzky, Duygu Akbas, Lukas Burger, Rabih Murr, Dirk Schubeler, Rudolf GrosschedlAbstract:Lymphopoiesis requires the activation of lineage-specific genes embedded in naive, inaccessible chromatin or in primed, accessible chromatin. The mechanisms responsible for de novo gain of chromatin accessibility, known as "pioneer" function, remain poorly defined. Here, we showed that the EBF1 C-terminal domain (CTD) is required for the regulation of a specific gene set involved in B cell fate decision and differentiation, independently of activation and repression functions. Using genome-wide analysis of DNaseI hypersensitivity and DNA methylation in multipotent EBF1(-/-) progenitors and derivative EBF1wt- or EBF1ΔC-expressing cells, we found that the CTD promoted chromatin accessibility and DNA demethylation in previously naive chromatin. The CTD allowed EBF1 to bind at inaccessible genomic regions that offer limited co-occupancy by other transcription factors, whereas the CTD was dispensable for EBF1 binding at regions that are occupied by multiple transcription factors. Thus, the CTD enables EBF1 to confer permissive lineage-specific changes in progenitor chromatin landscape.
Joseph R Ecker - One of the best experts on this subject based on the ideXlab platform.
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ethylene induced stabilization of ethylene insensitive3 and ein3 like1 is mediated by proteasomal degradation of ein3 binding f box 1 and 2 that requires ein2 in arabidopsis
The Plant Cell, 2010Co-Authors: Qiong Zhao, Joseph R Ecker, Zhiqiang Jiang, Chen Zhang, Ying Han, Yidong Liu, Shuqun Zhang, Hongwei GuoAbstract:Plant responses to ethylene are mediated by regulation of EBF1/2-dependent degradation of the ETHYLENE INSENSITIVE3 (EIN3) transcription factor. Here, we report that the level of EIL1 protein is upregulated by ethylene through an EBF1/2-dependent pathway. Genetic analysis revealed that EIL1 and EIN3 cooperatively but differentially regulate a wide array of ethylene responses, with EIL1 mainly inhibiting leaf expansion and stem elongation in adult plants and EIN3 largely regulating a multitude of ethylene responses in seedlings. When EBF1 and EBF2 are disrupted, EIL1 and EIN3 constitutively accumulate in the nucleus and remain unresponsive to exogenous ethylene application. Further study revealed that the levels of EBF1 and EBF2 proteins are downregulated by ethylene and upregulated by silver ion and MG132, suggesting that ethylene stabilizes EIN3/EIL1 by promoting EBF1 and EBF2 proteasomal degradation. Also, we found that EIN2 is indispensable for mediating ethylene-induced EIN3/EIL1 accumulation and EBF1/2 degradation, whereas MKK9 is not required for ethylene signal transduction, contrary to a previous report. Together, our studies demonstrate that ethylene similarly regulates EIN3 and EIL1, the two master transcription factors coordinating myriad ethylene responses, and clarify that EIN2 but not MKK9 is required for ethylene-induced EIN3/EIL1 stabilization. Our results also reveal that EBF1 and EBF2 act as essential ethylene signal transducers that by themselves are subject to proteasomal degradation.
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ethylene insensitive5 encodes a 5 3 exoribonuclease required for regulation of the ein3 targeting f box proteins EBF1 2
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Gabriela Olmedo, Hongwei Guo, Brian D Gregory, Saeid Nourizadeh, Laura Aguilarhenonin, Plinio Guzman, Joseph R EckerAbstract:Ethylene is a gaseous plant growth regulator that controls a multitude of developmental and stress responses. Recently, the levels of Arabidopsis EIN3 protein, a key transcription factor mediating ethylene-regulated gene expression, have been demonstrated to increase in response to the presence of ethylene gas. Furthermore, in the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F-box proteins, EBF1 and EBF2. Here we report the identification of ETHYLENE-INSENSITIVE5 as the 5′→3′ exoribonuclease XRN4. Specifically, we demonstrate that EIN5 is a component of the ethylene signal transduction cascade acting downstream of CTR1 that is required for ethylene-mediated gene expression changes. Furthermore, we find that the ethylene insensitivity of ein5 mutant plants is a consequence of the over-accumulation of EBF1 and EBF2 mRNAs resulting in the under-accumulation of EIN3 even in the presence of ethylene gas. Together, our results suggest that the role of EIN5 in ethylene perception is to antagonize the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay, which consequently allows the accumulation of EIN3 protein to trigger the ethylene response.
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plant responses to ethylene gas are mediated by scfEBF1 ebf2 dependent proteolysis of ein3 transcription factor
Cell, 2003Co-Authors: Joseph R EckerAbstract:Plants use ethylene gas as a signal to regulate myriad developmental processes and stress responses. The Arabidopsis EIN3 protein is a key transcription factor mediating ethylene-regulated gene expression and morphological responses. Here, we report that EIN3 protein levels rapidly increase in response to ethylene and this response requires several ethylene-signaling pathway components including the ethylene receptors (ETR1 and EIN4), CTR1, EIN2, EIN5, and EIN6. In the absence of ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F box proteins, EBF1 and EBF2. Plants containing mutations in either gene show enhanced ethylene response by stabilizing EIN3, whereas efb1 efb2 double mutants show constitutive ethylene phenotypes. Plants overexpressing either F box gene display ethylene insensitivity and destabilization of EIN3 protein. These results reveal that a ubiquitin/proteasome pathway negatively regulates ethylene responses by targeting EIN3 for degradation, and pinpoint EIN3 regulation as the key step in the response to ethylene.
Richard D Vierstra - One of the best experts on this subject based on the ideXlab platform.
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the arabidopsis ein3 binding f box proteins EBF1 and ebf2 have distinct but overlapping roles in ethylene signaling
The Plant Cell, 2007Co-Authors: Brad M Binder, Joseph M Walker, Jennifer M Gagne, Thomas J Emborg, Georg Hemmann, Anthony B Bleecker, Richard D VierstraAbstract:Ethylene signaling in Arabidopsis thaliana converges on the ETHYLENE-INSENSITIVE3 (EIN3)/EIN3-Like (EIL) transcription factors to induce various responses. EIN3 BINDING F-BOX1 (EBF1) and EBF2 were recently shown to function in ethylene perception by regulating EIN3/EIL turnover. In the absence of ethylene, EIN3 and possibly other EIL proteins are targeted for ubiquitination and subsequent degradation by Cullin 1–based E3 complexes containing EBF1 and 2. Ethylene appears to block this ubiquitination, allowing EIN3/EIL levels to rise and mediate ethylene signaling. Through analysis of mutant combinations affecting accumulation of EBF1, EBF2, EIN3, and EIL1, we show that EIN3 and EIL1 are the main targets of EBF1/2. Kinetic analyses of hypocotyl growth inhibition in response to ethylene and growth recovery after removal of the hormone revealed that EBF1 and 2 have temporally distinct but overlapping roles in modulating ethylene perception. Whereas EBF1 plays the main role in air and during the initial phase of signaling, EBF2 plays a more prominent role during the latter stages of the response and the resumption of growth following ethylene removal. Through their coordinated control of EIN3/EIL1 levels, EBF1 and EBF2 fine-tune ethylene responses by repressing signaling in the absence of the hormone, dampening signaling at high hormone concentrations, and promoting a more rapid recovery after ethylene levels dissipate.
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arabidopsis ein3 binding f box 1 and 2 form ubiquitin protein ligases that repress ethylene action and promote growth by directing ein3 degradation
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Jennifer M Gagne, Joseph M Walker, Shuichi Yanagisawa, Jan A Smalle, Derek J Gingerich, Richard D VierstraAbstract:Ubiquitination of various intracellular proteins by ubiquitin-protein ligases (or E3s) plays an essential role in eukaryotic cell regulation primarily through its ability to selectively target proteins for degradation by the 26S proteasome. Skp1, Cullin, F-box (SCF) complexes are one influential E3 class that use F-box proteins to deliver targets to a core ligase activity provided by the Skp1, Cullin, and Rbx1 subunits. Almost 700 F-box proteins can be found in Arabidopsis, indicating that SCF E3s likely play a pervasive role in plant physiology and development. Here, we describe the reverse genetic analysis of two F-box proteins, EBF1 and -2, that work coordinately in SCF complexes to repress ethylene action. Mutations in either gene cause hypersensitivity to exogenous ethylene and its precursor 1-aminocyclopropane-1-carboxylic acid. EBF1 and -2 interact directly with ethylene insensitive 3 (EIN3), a transcriptional regulator important for ethylene signaling. Levels of EIN3 are increased in mutants affecting either EBF1 or -2, suggesting that the corresponding SCF complexes work together in EIN3 breakdown. Surprisingly, double EBF1 ebf2 mutants display a substantial arrest of seedling growth and have elevated EIN3 levels, even in the absence of exogenous ethylene. Collectively, our results show that the SCFEBF1/EBF2-dependent ubiquitination and subsequent removal of EIN3 is critical not only for proper ethylene signaling but also for growth in plants.