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
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
Steroid hormones play essential roles in animal growth and development. Steroid signaling in animal system is focused on the direct gene regulation response mediated by its nuclear receptors. Recently, steroid hormone...Steroid hormones play essential roles in animal growth and development. Steroid signaling in animal system is focused on the direct gene regulation response mediated by its nuclear receptors. Recently, steroid hormones are also found in plants. Identification of BRI1 — a critical compo-nent of the plasma-membrane steroid receptor complex, and the related signal transduction pathway mediated by the membrane receptor have revealed an elementary picture of BR signaling from the cell surface perception to the activa-tion of BR-responsive nuclear genes.展开更多
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Steroid hormones play essential roles in animal growth and development. Steroid signaling in animal system is focused on the direct gene regulation response mediated by its nuclear receptors. Recently, steroid hormones are also found in plants. Identification of BRI1 — a critical compo-nent of the plasma-membrane steroid receptor complex, and the related signal transduction pathway mediated by the membrane receptor have revealed an elementary picture of BR signaling from the cell surface perception to the activa-tion of BR-responsive nuclear genes.
