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1.
The tomato Leu-rich repeat receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1) has been implicated in both peptide (systemin) and steroid (brassinosteroid [BR]) hormone perception. In an attempt to dissect these signaling pathways, we show that transgenic expression of BRI1 can restore the dwarf phenotype of the tomato curl3 (cu3) mutation. Confirmation that BRI1 is involved in BR signaling is highlighted by the lack of BR binding to microsomal fractions made from cu3 mutants and the restoration of BR responsiveness following transformation with BRI1. In addition, wound and systemin responses in the cu3 mutants are functional, as assayed by proteinase inhibitor gene induction and rapid alkalinization of culture medium. However, we observed BRI1-dependent root elongation in response to systemin in Solanum pimpinellifolium. In addition, ethylene perception is required for normal systemin responses in roots. These data taken together suggest that cu3 is not defective in systemin-induced wound signaling and that systemin perception can occur via a non-BRI1 mechanism. 相似文献
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Small signaling molecules that mediate cell-cell communication are essential for developmental regulation in multicellular organisms. Among them are the steroids and peptide hormones that regulate growth in both plants and animals. In plants, brassinosteroids (BRs) are perceived by the cell surface receptor kinase BRI1, which is distinct from the animal steroid receptors. Identification of components of the BR signaling pathway has revealed similarities to other animal and plant signal transduction pathways. Recent studies demonstrated that tomato BRI1 (tBRI1) perceives both BR and the peptide hormone systemin, raising new questions about the molecular mechanism and evolution of receptor-ligand specificity. 相似文献
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Choe S Schmitz RJ Fujioka S Takatsuto S Lee MO Yoshida S Feldmann KA Tax FE 《Plant physiology》2002,130(3):1506-1515
Mutants defective in the biosynthesis or signaling of brassinosteroids (BRs), plant steroid hormones, display dwarfism. Loss-of-function mutants for the gene encoding the plasma membrane-located BR receptor BRI1 are resistant to exogenous application of BRs, and characterization of this protein has contributed significantly to the understanding of BR signaling. We have isolated two new BR-insensitive mutants (dwarf12-1D and dwf12-2D) after screening Arabidopsis ethyl methanesulfonate mutant populations. dwf12 mutants displayed the characteristic morphology of previously reported BR dwarfs including short stature, short round leaves, infertility, and abnormal de-etiolation. In addition, dwf12 mutants exhibited several unique phenotypes, including severe downward curling of the leaves. Genetic analysis indicates that the two mutations are semidominant in that heterozygous plants show a semidwarf phenotype whose height is intermediate between wild-type and homozygous mutant plants. Unlike BR biosynthetic mutants, dwf12 plants were not rescued by high doses of exogenously applied BRs. Like bri1 mutants, dwf12 plants accumulated castasterone and brassinolide, 43- and 15-fold higher, respectively, providing further evidence that DWF12 is a component of the BR signaling pathway that includes BRI1. Map-based cloning of the DWF12 gene revealed that DWF12 belongs to a member of the glycogen synthase kinase 3beta family. Unlike human glycogen synthase kinase 3beta, DWF12 lacks the conserved serine-9 residue in the auto-inhibitory N terminus. In addition, dwf12-1D and dwf12-2D encode changes in consecutive glutamate residues in a highly conserved TREE domain. Together with previous reports that both bin2 and ucu1 mutants contain mutations in this TREE domain, this provides evidence that the TREE domain is of critical importance for proper function of DWF12/BIN2/UCU1 in BR signal transduction pathways. 相似文献
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Jie Wang Jianjun Jiang Jue Wang Lei Chen Shi-Long Fan Jia-Wei Wu Xuelu Wang Zhi-Xin Wang 《Cell research》2014,24(11):1328-1341
Brassinosteroids (BRs) are essential steroid hormones that have crucial roles in plant growth and development. BRs are perceived by the cell-surface receptor-like kinase brassinosteroid insensitive 1 (BRI1). In the absence of BRs, the cytosolic kinase domain (KD) of BRI1 is inhibited by its auto-inhibitory carboxyl terminus, as well as by interacting with an inhibitor protein, BRI1 kinase inhibitor 1 (BKI1). How BR binding to the extracellular domain of BRI1 leads to activation of the KD and dissociation of BKI1 into the cytosol remains unclear. Here we report the crystal structure of BRI1 KD in complex with the interacting peptide derived from BKI1. We also provide biochemical evidence that BRI1-associated kinase 1 (BAK1) plays an essential role in initiating BR signaling. Steroid-dependent heterodimerization of BRI1 and BAK1 ectodomains brings their cytoplasmic KDs in the right orientation for competing with BKI1 and transphosphorylation. 相似文献
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Wang H Yang C Zhang C Wang N Lu D Wang J Zhang S Wang ZX Ma H Wang X 《Developmental cell》2011,21(5):825-834
The plasma membrane-localized plant steroid hormone receptor, BRASSINOSTEROID INSENSITIVE 1 (BRI1), is quiescent in the absence of steroids, largely due to a negative regulator, BRI1 KINASE INHIBITOR 1 (BKI1). Here, we report that the steroid-induced, plasma membrane-dissociated and phosphorylated BKI1 also plays positive roles in BR signaling by interacting with a subset of 14-3-3 proteins. The cytosolic fraction of BKI1 carboxyl terminal region enhances BR signaling. Mutations of two serine residues in this region lead to reduced phosphorylation by the BRI1 kinase and constitutive plasma membrane localization. The 14-3-3 proteins can interact with the phosphorylated BKI1 through a motif that contains the two phosphorylation sites to release inhibition of BRI1 by BKI1. Meanwhile, the cytosolic BKI1 antagonizes the 14-3-3?s and enhances accumulation of BRI1 EMS SUPPRESSOR 1 (BES1)/BRASSINAZOLE RESISTANT 1 (BZR1) in the nucleus to regulate BR-responses. 相似文献
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Nicholas Holton Kate Harrison Takao Yokota Gerard J Bishop 《Plant signaling & behavior》2008,3(1):54-55
Brassinosteroids (BRs) are perceived by Brassinosteroid Insensitive 1 (BRI1), that encodes a leucine-rich repeat receptor kinase. Tomato BRI1 has previously been implicated in both systemin and BR signalling. The role of tomato BRI1 in BR signalling was confirmed, however it was found not to be essential for systemin/wound signalling. Tomato roots were shown to respond to systemin but this response varied according to the species and growth conditions. Overall the data indicates that mutants defective in tomato BRI1 are not defective in systemin-induced wound signalling and that systemin perception can occur via a non-BRI1 mechanism.Key words: tomato BRI1, brassinosteroids, systemin, wound signallingBrassinosteroids (BRs) are steroid hormones that are essential for normal plant growth. The most important BR receptor in Arabidopsis is BRASSINOSTERIOD INSENSITIVE 1 (BRI1), a serine/threonine kinase with a predicted extracellular domain of ∼24 leucine-rich repeats (LRRs).1,2 BRs bind to BRI1 via a steroid-binding domain that includes LRR 21 and a so-called “island” domain.2,3 In tomato a BRI1 orthologue has been identified that when mutated, as in the curl3 (cu3) mutation, results in BR-insensitive dwarf plants.4 Tomato BRI1 has also been purified as a systemin-binding protein.5 Systemin is an eighteen amino acid peptide, which is produced by post-translational cleavage of prosystemin. Systemin has been implicated in wound signalling and is able to induce the production of jasmonate, protease inhibitors (PIN) and rapid alkalinization of cell suspensions (reviewed in ref. 6).To clarify whether tomato BRI1 was indeed a dual receptor it was important to first confirm its role in BR signalling. Initially this was carried out by genetic complementation of the cu3 mutant phenotype.7 Overexpression of tomato BRI1 restored the dwarf phenotype and BR sensitivity and normalized BR levels (35S:TomatoBRI1 complemented line Wt* cu3* 6-deoxocathasterone 566 964 676 6-deoxoteasterone nd 47 48 3-dehydro-6-deoxoteasterone 87 62 69 6-deoxotyphasterol nd 588 422 6-deoxocastasterone 1,755 6,247 26,210 castasterone 255 637 17,428 brassinolide nd nd nd