Brassinosteroids( BRs),a group of polyhydroxylated plant steroid hormones,have fundamental functions in many aspects of plant growth and development. The BRI1-EMS SUPPRESSOR1( BES1) transcription factor is a positive ...Brassinosteroids( BRs),a group of polyhydroxylated plant steroid hormones,have fundamental functions in many aspects of plant growth and development. The BRI1-EMS SUPPRESSOR1( BES1) transcription factor is a positive regulator involved in BRs signaling pathways. We studied the role of At BES1D( obtained from bes1-D Arabidopsis) in tomato( Solanum lycopersicum) seed germination. Overexpression of At BES1D in tomato inhibited seed germination compared with wild type Zhongshusihao( ZS4). The expression of abscisic acid( ABA) related genes was enhanced in At BES1D transgenic tomato seeds during germination.Furthermore,At BES1D transgenic tomato seeds were hypersensitive to ABA. Our findings suggest that the inhibitory effect of At BES1D transcription factor on tomato seed germination may be correlated with an enhanced ABA pathway.展开更多
Plants utilize plasma membrane-localized receptor-like kinases （RLKs） to sense extracellular signals to coordinate growth, development, and innate immune responses. BAK1 regulates multiple signaling pathways acting ...Plants utilize plasma membrane-localized receptor-like kinases （RLKs） to sense extracellular signals to coordinate growth, development, and innate immune responses. BAK1 regulates multiple signaling pathways acting as a co-receptor of several distinct ligand-binding RLKs. It has been debated whether BAK1 serves as an essential regulatory component or only a signal amplifier without pathway specificity. This issue has been clarified recently. Genetic and structural analyses indicated that BAK1 and its homologs play indispensible roles in mediating brassinosteroid （BR） signaling pathway by directly perceiving the ligand BR and activating the receptor of BR, BRII. The mechanism revealed by these studies now serves as a paradigm for how a pair of RLKs can function together in ligand binding and subsequent initiation of signaling.展开更多
The major brassinosteroid （BR） receptor of Arabidopsis BRASSINOSTEROID INSENSITIVE1 （BRI1） plays fundamental roles in BR signaling, but the molecular mechanisms underlying the effects of BR on BRI1 internalization...The major brassinosteroid （BR） receptor of Arabidopsis BRASSINOSTEROID INSENSITIVE1 （BRI1） plays fundamental roles in BR signaling, but the molecular mechanisms underlying the effects of BR on BRI1 internalization and assembly state remain unclear. Here, we applied variable angle total internal reflection fluorescence microscopy and fluorescence cross-correlation spectroscopy to analyze the dynamics of GFP-tagged BRII. We found that, in response to BR, the degree of co-localization of BRI1-GFP with AtFIotl-mCherry increased, and especially BR stimulated the membrane microdomain-associated pathway of BRI1 internalization. We also verified these observations in endocytosis-defective chc2-1 mutants and the AtFIotl amiRNA 15-5 lines. Furthermore, examination of the phosphorylation status of bril-EMS-suppressor 1 and measurement of BR-responsive gene expression revealed that membrane microdomains affect BR signaling. These results suggest that BR promotes the partitioning of BRI1 into functional membrane microdomains to activate BR signaling.展开更多
Brassinosteroid （BR） binding activates the receptor kinase BRI1 by inducing heterodimerization with its co- receptor kinase BAK1; however, the mechanisms that reversibly inactivate BRI1 remain unclear. Here we show ...Brassinosteroid （BR） binding activates the receptor kinase BRI1 by inducing heterodimerization with its co- receptor kinase BAK1; however, the mechanisms that reversibly inactivate BRI1 remain unclear. Here we show that cytoplasm-localized protein phosphatase 2A （PP2A） B＇ regulatory subunits interact with BRI1 to mediate its dephosphorylation and inactivation. Loss-of-function and overexpression experiments showed that a group of PP2A B＇ regulatory subunits, represented by B＇η, negatively regulate BR signaling by decreasing BRI1 phosphorylation. BR increases the expression levels of these B＇ subunits, and B/TI interacts preferentially with phosphorylated BRI1, suggesting that the dynamics of BR signaling are modu- lated by the PP2A-mediated feedback inactivation of BRI1. Compared with PP2A B＇α and B＇β, which promote BR responses by dephosphorylating the downstream transcription factor BZR1, the BRI1- inactivating B＇ subunits showed similar binding to BRI1 and BZR1 but distinct subcellular localization. Alteration of the nuclear/cytoplasmic localization of the B＇ subunits revealed that cytoplasmic PP2A de- phosphorylates BRI1 and inhibits the BR response, whereas nuclear PP2A dephosphorylates BZR1 and ac- tivates the BR response. Our findings not only identify the PP2A regulatory B subunits that mediate the binding and dephosphorylation of BRI1, but also demonstrate that the subcellular localization of PP2A specifies its substrate selection and distinct effects on BR signaling.展开更多
Mutation of the immunophilin-like FK506-binding protein TWlSTED DWARF1 （FKBP42/TWD1） causes dwarf and twisted-organ phenotypes in Arabidopsis. However, the function of FKBP42 is not fully understood at the molecular...Mutation of the immunophilin-like FK506-binding protein TWlSTED DWARF1 （FKBP42/TWD1） causes dwarf and twisted-organ phenotypes in Arabidopsis. However, the function of FKBP42 is not fully understood at the molecular level. Using genetic, physiological, and immunological experiments, we show here that FKBP42/TWD1 is necessary for brassinosteroid （BR） signal transduction. The twdl mutant showed reduced BR sensitivity in growth responses and activation of the BZR1 transcription factor. However, twdl showed normal responses to an inhibitor of BIN2/GSK3, suggesting that twdl has a defect upstream of BIN2 in the BR signaling pathway. In vitro and in vivo assays showed that TWD1 interacts physically with the kinase domains of the BR receptor kinases BRI1 and BAK1. TWD1 is not required for normal localization of BRI1-GFP to the plasma membrane or for activation of the flagellin receptor kinase FLS2. Our results suggest that FKBP42/TWD1 plays a specific role in the activation of BRI1 receptor kinase.展开更多
The brassinosteroid （BR） receptor, BR insensitive 1 （BRI1）, plays a critical role in plant development, but whether BRI1-mediated BR signaling is involved in plant defense responses to herbivores was largely unkno...The brassinosteroid （BR） receptor, BR insensitive 1 （BRI1）, plays a critical role in plant development, but whether BRI1-mediated BR signaling is involved in plant defense responses to herbivores was largely unknown. Here, we examined the function of BRI1 in the resistance of Nicotiana attenuata （Solanaceae） to its specialist insect herbivore Manduca sexta. Jasmonic acid （JA） and JA-isoleucine conjugate （JA-Ile） are important hormones that mediate resistance to herbivores and we found that after wounding or simulated herbivory NaBRI1 had little effect on JA levels, but was important for the induction of JA-Ile. Further experiments revealed that decreased JAR （the enzyme for JA-Ile production） activity and availability of Ile in NaBRI1-silenced plants were likely responsible for the low JA-Ile levels. Consistently, M. sexta larvae gained more weight on NaBRI1-silenced plants than on the control plants. Quantification of insect feeding-induced secondary metabolites revealed that silencing NaBRI1 resulted in decreased levels of carbon-rich defensive secondary metabolites （hydroxygeranyllinalool diterpene glycosides, chlorogenic acid, and rutin）, but had little effect on the nitrogen-rich ones （nicotine and trypsin proteinase inhibitors）. Thus, NaBRI1-mediated BR signaling is likely involved in plant defense responses to M. sexta, including maintaining JA-Ile levels and the accumulation of several carbon-rich defensive secondary metabolites.展开更多
Agrobacterium-mediated transformation is widely used in transgenic plant engineering and has been proven to be a powerful tool for insertional mutagenesis of the plant gsnome. The transferred DNA （T-DNA） from Agroba...Agrobacterium-mediated transformation is widely used in transgenic plant engineering and has been proven to be a powerful tool for insertional mutagenesis of the plant gsnome. The transferred DNA （T-DNA） from Agrobacterium is integrated into the plant genome through illegitimate recombination between the T-DNA and the plant DNA. Contrasting to the canonical insertion, here we report on a locus showing a complex mutation associated with T-DNA insertion at the BRI1 gene in Arabidopsis thaliana. We obtained a mutant line, named salads for its phenotype of dwarf stature and proliferating rosette. Molecular characterization of this mutant revealed that in addition to T-DNA a non-T-DNA-Iocalized transposon from bacteria was inserted in the Arabidopsis genome and that a region of more than 11.5 kb of the Arabidopsis genome was deleted at the insertion site. The deleted region contains the braesinosteroid receptor gene BRI1 and the transcription factor gene WRKY13. Our finding reveals non-canonical T-DNA insertion, implicating horizontal gene transfer and cautioning the use of T-DNA as mutagen in transgenic research.展开更多
基金We thank Prof Joanne Chory （The Salk Institute for Biological Studies, USA） for providing the Arabidopsis bril-101 mutant seeds. This work was supported by grants from the National Natural Science Foundation of China （grant numbers： 30070074, 30330040 and 30570161）.
基金Supported by National Undergraduate Training Program for Innovation and Entrepreneurship (2018A8205)。
文摘Brassinosteroids( BRs),a group of polyhydroxylated plant steroid hormones,have fundamental functions in many aspects of plant growth and development. The BRI1-EMS SUPPRESSOR1( BES1) transcription factor is a positive regulator involved in BRs signaling pathways. We studied the role of At BES1D( obtained from bes1-D Arabidopsis) in tomato( Solanum lycopersicum) seed germination. Overexpression of At BES1D in tomato inhibited seed germination compared with wild type Zhongshusihao( ZS4). The expression of abscisic acid( ABA) related genes was enhanced in At BES1D transgenic tomato seeds during germination.Furthermore,At BES1D transgenic tomato seeds were hypersensitive to ABA. Our findings suggest that the inhibitory effect of At BES1D transcription factor on tomato seed germination may be correlated with an enhanced ABA pathway.
基金supported by the grants from the National Natural Science Foundation of China to J.L.(91117008 and 90917019)National Basic Research Program of China to J.L.(2011CB915401)Fundamental Research Funds for the Central Universities to S.X.(lzujbky-2009-35)
文摘Plants utilize plasma membrane-localized receptor-like kinases （RLKs） to sense extracellular signals to coordinate growth, development, and innate immune responses. BAK1 regulates multiple signaling pathways acting as a co-receptor of several distinct ligand-binding RLKs. It has been debated whether BAK1 serves as an essential regulatory component or only a signal amplifier without pathway specificity. This issue has been clarified recently. Genetic and structural analyses indicated that BAK1 and its homologs play indispensible roles in mediating brassinosteroid （BR） signaling pathway by directly perceiving the ligand BR and activating the receptor of BR, BRII. The mechanism revealed by these studies now serves as a paradigm for how a pair of RLKs can function together in ligand binding and subsequent initiation of signaling.
文摘The major brassinosteroid （BR） receptor of Arabidopsis BRASSINOSTEROID INSENSITIVE1 （BRI1） plays fundamental roles in BR signaling, but the molecular mechanisms underlying the effects of BR on BRI1 internalization and assembly state remain unclear. Here, we applied variable angle total internal reflection fluorescence microscopy and fluorescence cross-correlation spectroscopy to analyze the dynamics of GFP-tagged BRII. We found that, in response to BR, the degree of co-localization of BRI1-GFP with AtFIotl-mCherry increased, and especially BR stimulated the membrane microdomain-associated pathway of BRI1 internalization. We also verified these observations in endocytosis-defective chc2-1 mutants and the AtFIotl amiRNA 15-5 lines. Furthermore, examination of the phosphorylation status of bril-EMS-suppressor 1 and measurement of BR-responsive gene expression revealed that membrane microdomains affect BR signaling. These results suggest that BR promotes the partitioning of BRI1 into functional membrane microdomains to activate BR signaling.
文摘Brassinosteroid （BR） binding activates the receptor kinase BRI1 by inducing heterodimerization with its co- receptor kinase BAK1; however, the mechanisms that reversibly inactivate BRI1 remain unclear. Here we show that cytoplasm-localized protein phosphatase 2A （PP2A） B＇ regulatory subunits interact with BRI1 to mediate its dephosphorylation and inactivation. Loss-of-function and overexpression experiments showed that a group of PP2A B＇ regulatory subunits, represented by B＇η, negatively regulate BR signaling by decreasing BRI1 phosphorylation. BR increases the expression levels of these B＇ subunits, and B/TI interacts preferentially with phosphorylated BRI1, suggesting that the dynamics of BR signaling are modu- lated by the PP2A-mediated feedback inactivation of BRI1. Compared with PP2A B＇α and B＇β, which promote BR responses by dephosphorylating the downstream transcription factor BZR1, the BRI1- inactivating B＇ subunits showed similar binding to BRI1 and BZR1 but distinct subcellular localization. Alteration of the nuclear/cytoplasmic localization of the B＇ subunits revealed that cytoplasmic PP2A de- phosphorylates BRI1 and inhibits the BR response, whereas nuclear PP2A dephosphorylates BZR1 and ac- tivates the BR response. Our findings not only identify the PP2A regulatory B subunits that mediate the binding and dephosphorylation of BRI1, but also demonstrate that the subcellular localization of PP2A specifies its substrate selection and distinct effects on BR signaling.
文摘Mutation of the immunophilin-like FK506-binding protein TWlSTED DWARF1 （FKBP42/TWD1） causes dwarf and twisted-organ phenotypes in Arabidopsis. However, the function of FKBP42 is not fully understood at the molecular level. Using genetic, physiological, and immunological experiments, we show here that FKBP42/TWD1 is necessary for brassinosteroid （BR） signal transduction. The twdl mutant showed reduced BR sensitivity in growth responses and activation of the BZR1 transcription factor. However, twdl showed normal responses to an inhibitor of BIN2/GSK3, suggesting that twdl has a defect upstream of BIN2 in the BR signaling pathway. In vitro and in vivo assays showed that TWD1 interacts physically with the kinase domains of the BR receptor kinases BRI1 and BAK1. TWD1 is not required for normal localization of BRI1-GFP to the plasma membrane or for activation of the flagellin receptor kinase FLS2. Our results suggest that FKBP42/TWD1 plays a specific role in the activation of BRI1 receptor kinase.
文摘The brassinosteroid （BR） receptor, BR insensitive 1 （BRI1）, plays a critical role in plant development, but whether BRI1-mediated BR signaling is involved in plant defense responses to herbivores was largely unknown. Here, we examined the function of BRI1 in the resistance of Nicotiana attenuata （Solanaceae） to its specialist insect herbivore Manduca sexta. Jasmonic acid （JA） and JA-isoleucine conjugate （JA-Ile） are important hormones that mediate resistance to herbivores and we found that after wounding or simulated herbivory NaBRI1 had little effect on JA levels, but was important for the induction of JA-Ile. Further experiments revealed that decreased JAR （the enzyme for JA-Ile production） activity and availability of Ile in NaBRI1-silenced plants were likely responsible for the low JA-Ile levels. Consistently, M. sexta larvae gained more weight on NaBRI1-silenced plants than on the control plants. Quantification of insect feeding-induced secondary metabolites revealed that silencing NaBRI1 resulted in decreased levels of carbon-rich defensive secondary metabolites （hydroxygeranyllinalool diterpene glycosides, chlorogenic acid, and rutin）, but had little effect on the nitrogen-rich ones （nicotine and trypsin proteinase inhibitors）. Thus, NaBRI1-mediated BR signaling is likely involved in plant defense responses to M. sexta, including maintaining JA-Ile levels and the accumulation of several carbon-rich defensive secondary metabolites.
基金Supported by the postdoctoral fellowship from the French Ministère dela Recherche et des Nouvelles Technologies to Z.Zhaothe foreign-student fellowship from the French Ministère de l'Education Nationale,del'Enseignement Supérieur et de la Recherche to Y.Zhuthe CentreNational de la Recherche Scientifique(CNRS)to W.H.Shen.
文摘Agrobacterium-mediated transformation is widely used in transgenic plant engineering and has been proven to be a powerful tool for insertional mutagenesis of the plant gsnome. The transferred DNA （T-DNA） from Agrobacterium is integrated into the plant genome through illegitimate recombination between the T-DNA and the plant DNA. Contrasting to the canonical insertion, here we report on a locus showing a complex mutation associated with T-DNA insertion at the BRI1 gene in Arabidopsis thaliana. We obtained a mutant line, named salads for its phenotype of dwarf stature and proliferating rosette. Molecular characterization of this mutant revealed that in addition to T-DNA a non-T-DNA-Iocalized transposon from bacteria was inserted in the Arabidopsis genome and that a region of more than 11.5 kb of the Arabidopsis genome was deleted at the insertion site. The deleted region contains the braesinosteroid receptor gene BRI1 and the transcription factor gene WRKY13. Our finding reveals non-canonical T-DNA insertion, implicating horizontal gene transfer and cautioning the use of T-DNA as mutagen in transgenic research.
