Intragenic Suppression of a Trafficking-Defective Brassinosteroid Receptor Mutant in Arabidopsis

Belkhadir, Youssef; Durbak, Amanda; Wierzba, Michael; Schmitz, Robert J.; Aguirre, Andrea Martinez; Michel, René P.; Rowe, Scott C.; Fujioka, Shozo; Tax, Frans E.

doi:10.1534/genetics.109.111898

Cited by 19 publications

(18 citation statements)

References 54 publications

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“…The homozygous mutations of BRI1 and FLS2 and the sequence of the insertion site were confirmed by PCR and sequencing. The bri1 mutant was confirmed to be a null allele by Western blot using native anti-BRI1 polyclonal antibody against the C terminus of BRI1 (26). The functional FLS2prom:FLS2::GFP in the Col-0 background is a gift from Silke Robatzek (The Sainsbury Laboratory, Norwich, UK) (9).…”

Section: Methodsmentioning

confidence: 99%

“…Monoclonal anti-GFP HRP-coupled (Miltenyi Biotech), anti-HA-HRP coupled (Miltenyi Biotech), anti-ACTIN (clone C4; MP Biomedicals), and polyclonal anti-CHERRY (DsRed polyclonal; Clontech) were used at 1:5,000. Polyclonal anti-BRI1 [raised against BRI1 C terminus in rabbit) (26)] was used at 1:1,000. Flg22 treatment before protein extraction was done in liquid medium (0.5× Linsmaier and Skoog medium) for 5 min under vacuum.…”

Section: Methodsmentioning

confidence: 99%

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Extracellular leucine-rich repeats as a platform for receptor/coreceptor complex formation

Jaillais

Belkhadir

Balsemão-Pires

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Receptor kinases with leucine-rich repeat (LRR) extracellular domains form the largest family of receptors in plants. In the few cases for which there is mechanistic information, ligand binding in the extracellular domain often triggers the recruitment of a LRRcoreceptor kinase. The current model proposes that this recruitment is mediated by their respective kinase domains. Here, we show that the extracellular LRR domain of BRI1-ASSOCIATED KINASE1 (BAK1), a coreceptor involved in the disparate processes of cell surface steroid signaling and immunity in plants, is critical for its association with specific ligand-binding LRR-containing receptors. The LRRs of BAK1 thus serve as a platform for the molecular assembly of signalcompetent receptors. We propose that this mechanism represents a paradigm for LRR receptor activation in plants. -5). Ligand perception at the cell surface by either BRI1 or FLS2 induces the subsequent recruitment of BAK1 to a ligand-bound receptor complex (6-10). This process triggers transphosphorylation at multiple serines and threonines of the respective kinase domains inside the cell (11-13). Perhaps because BRI1 is a long-lived protein that apparently cycles between the plasma membrane and endosomes (14), there are multiple mechanisms to maintain the kinase domain in a basal state. BRI1 kinase is auto-inhibited by its C-terminal tail (15), by auto-phosphorylation on threonine 872 (11), and by a protein, BRI1 KINASE INHIBITOR 1 (BKI1), which associates with BRI1's kinase domain (10, 16). BKI1 inhibits BR signaling by binding to the BRI1's kinase domain, thereby inhibiting the interaction between BRI1-and BAK1-kinase (10, 16). Upon ligand binding, BRI1 phosphorylates BKI1 on a tyrosine within its membrane-targeting region, which dissociates BKI1 from the cell membrane and targets it to the cytoplasm, where it is inactive (10). Dissociation of BKI1 from BRI1 allows formation of a stable BRI1-BAK1 complex that is competent to induce downstream signaling (17).The interplay between BRI1 and BAK1 kinase domains is further regulated by BAK1 autophosphorylation on tyrosine 610 (tyr-610), which is required to stimulate BRI1 kinase activity in vitro and for proper BR signaling in vivo (18). Of note, BAK1 tyr-610 phosphorylation is not required for flagellin response and it is possible that tyr-610 phosphorylation might be involved in the proper interaction with its cognate receptors. However, tyr-610 mutations affect only BRI1 kinase activation but not its interaction with BRI1 intracellular domain (18). Therefore, a critical unanswered question is how ligand-bound LRR-RKs selectively recruit BAK1. Here, we report that the LRR domain of BAK1 is required for its recruitment to a ligand-bound LRR-RK and allows the kinase domains to be in physical contact for subsequent reciprocal transphosphorylation. Furthermore, our data indicate that the extracellular domain (ECD) of BAK1 is critical for the high affinity formation of the correct receptor/coreceptor pair.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Extracellular leucine-rich repeats as a platform for receptor/coreceptor complex formation

Jaillais

Belkhadir

Balsemão-Pires

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

142

140

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“…Sample preparation and imaging were performed as described by Belkhadir et al (2010). Stage 3 floral meristem height was measured as the distance between the interior base of the medial sepal primordia and the top of the dome, and width was measured as the distance between sepal primordia ( Figure S2).…”

Section: Histological Analysismentioning

confidence: 99%

CLAVATA Signaling Pathway Receptors of Arabidopsis Regulate Cell Proliferation in Fruit Organ Formation as well as in Meristems

Durbak

Tax

2011

Genetics

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The CLAVATA1 (CLV1), CLV2, and CORYNE (CRN) receptors in Arabidopsis thaliana maintain cell proliferation in shoot apical meristems by restricting expression of the transcription factor WUSCHEL (WUS). Previously characterized receptor mutants generate extra fruit and floral organs that are proposed to arise from enlarged floral meristems (FMs). We identified new alleles in clv1, clv2, and crn and found that most mutants produce only extra fruit organs and generate FMs of similar dimensions as wild type. Characterization of gynoecium development in receptor mutants revealed increased cell proliferation and ectopic fruit organ initiation after FM termination. These regions of increased cell division also display expanded expression of the cell proliferation-promoting transcription factor SHOOTMERISTEMLESS (STM), similar to the expansion of WUS expression in the shoot apical meristems of strong clv1 mutants. We also examined genetic interactions between the ERECTA (ER) and BARELY ANY MERISTEM 1 (BAM1) receptor-like kinases and CLV pathway receptors. Our results suggest a model in which CLV1/BAM1 and CLV2/CRN complexes act in separate, parallel pathways in shoot meristems, while the CLV1, CLV2, and CRN receptors function together in a linear pathway during fruit development. These results demonstrate the importance of regulating cell proliferation in plants that undergo organogenesis throughout their life cycle.

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“…S1). This rules out the possibility, for example, that the Y831F mutant protein somehow specifically stabilizes the BRI1-5 protein, which is a functional BRI1 receptor that is normally retained in the endoplasmic reticulum, where it is degraded (Hong et al, 2008;Belkhadir et al, 2010). Thus, the Y831F phenotype is not background specific, but for simplicity the remainder of these studies are focused on comparisons between wild-type BRI1-Flag and the Y831F mutant in the bri1-5 background.…”

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confidence: 99%

Enhancing Arabidopsis Leaf Growth by Engineering the BRASSINOSTEROID INSENSITIVE1 Receptor Kinase

Sun

et al. 2011

Plant Physiology

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The BRASSINOSTEROID INSENSITIVE1 (BRI1) receptor kinase has recently been shown to possess tyrosine kinase activity, and preventing autophosphorylation of the tyrosine-831 regulatory site by site-directed mutagenesis enhances shoot growth. In this study, we characterized the increased leaf growth of Arabidopsis (Arabidopsis thaliana) plants expressing BRI1(Y831F)-Flag compared with BRI1-Flag (both driven by the native promoter and expressed in the bri1-5 weak allele background) and provide insights into the possible mechanisms involved. On average, relative leaf growth rate was increased 16% in the Y831F plants (in the bri1-5 background), and the gain of function of the Y831F-directed mutant was dominant in the wild-type background. Leaves were larger as a result of increased cell numbers and had substantially increased vascularization. Transcriptome analysis indicated that genes associated with brassinolide biosynthesis, secondary cell wall biosynthesis and vascular development, and regulation of growth were altered in expression and may contribute to the observed changes in leaf architecture and whole plant growth. Analysis of gas exchange and chlorophyll fluorescence indicated that Y831F mutant plants had higher rates of photosynthesis, and metabolite analysis documented enhanced accumulation of starch, sucrose, and several amino acids, most prominently glycine and proline. These results demonstrate that mutation of BRI1 can enhance photosynthesis and leaf growth/vascularization and may suggest new approaches to increase whole plant carbon assimilation and growth.Brassinosteroids (BRs) are essential plant steroid hormones that regulate multiple aspects of growth and development, including cell elongation, cell division, vascular differentiation, seed germination, timing of senescence, male fertility, and organ formation (Clouse and Sasse, 1998; Altmann, 1999;Nakaya et al., 2002;Gonzalez et al., 2010). It is known that BRs bind to the BRASSINOSTEROID-INSENSITIVE1 (BRI1) receptor kinase, which functions in conjunction with the coreceptor BRASSINOSTEROID-ASSOCIATED KINASE1 (BAK1) in hormone perception and signal transduction Nam and Li, 2002). The BR signal transduction pathway ultimately controls the phosphorylation status of the transcription factors BZR1 and BZR2/BES1 in the nucleus (Kim et al., 2009) and thereby regulates the expression of more than 700 genes in Arabidopsis (Arabidopsis thaliana; Goda et al., 2002;Mü ssig et al., 2002;Vert et al., 2005). Many specific components of the signal transduction pathway have been identified and have recently been reviewed (Kim and Wang, 2010;Tang et al., 2010).BRs are now considered essential chemical signals and plant hormones, and accordingly, manipulation of endogenous BR content or BR signaling has a profound effect on plant growth. For example, overexpression of DWARF4, which encodes an enzyme that catalyzes a rate-limiting step in BR biosynthesis, enhances plant growth and seed yield in Arabidopsis (Choe et al., 2001), while down-regulation of BR biosynthesis...

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Intragenic Suppression of a Trafficking-Defective Brassinosteroid Receptor Mutant in Arabidopsis

Cited by 19 publications

References 54 publications

Extracellular leucine-rich repeats as a platform for receptor/coreceptor complex formation

Extracellular leucine-rich repeats as a platform for receptor/coreceptor complex formation

CLAVATA Signaling Pathway Receptors of Arabidopsis Regulate Cell Proliferation in Fruit Organ Formation as well as in Meristems

Enhancing Arabidopsis Leaf Growth by Engineering the BRASSINOSTEROID INSENSITIVE1 Receptor Kinase

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