Nucleocytoplasmic Shuttling of BZR1 Mediated by Phosphorylation Is Essential in<i>Arabidopsis</i>Brassinosteroid Signaling

Ryu, Hojin; Kim, Kang-Min; Cho, Hyunwoo; Park, Joonghyuk; Choe, Sung Sik; Hwang, Ildoo

doi:10.1105/tpc.107.053728

Cited by 299 publications

(306 citation statements)

References 46 publications

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“…BIN2 kinase activity can be measured by BRASSINAZOLE RESISTANT 1 (BZR1)-CFP movement from the nucleus to cytoplasm as a sensor [27][28][29][30] . Overexpression of BIN2 reduced nuclear localization of BZR1-CFP in N. benthamiana epidermis and this reduction was overcome by suppression of BIN2 activity with bikinin, a plant GSK3 specific inhibitor (Fig.…”

Section: Bin2 Interacts With Tdr Cytoplasmic Domain In Y2h Assaymentioning

confidence: 99%

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF–TDR signalling

et al. 2014

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Section: Bin2 Interacts With Tdr Cytoplasmic Domain In Y2h Assaymentioning

confidence: 99%

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF–TDR signalling

et al. 2014

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“…Interestingly, we observed that BSU1, a kelch-repeat phosphatase, facilitates dephosphorylation and nuclear translocation of BZR1. 13,15 although Mora-Garcia et al reported that BSU1 is constitutively localized in the nucleus, 12 we found that BSU1 localizes to both the nucleus and cytoplasm in protoplasts (data not shown). detailed examination of BSU1 localization in different tissues and developmental stages will be important to fully understand its roles in BR signaling, particularly in regard to the spatial distribution of BZR1.…”

Section: Spatial Redistribution Of Key Transcriptional Regulators In mentioning

confidence: 47%

“…Physiological analysis of BZR1 S130/134A , BZR1 S173A , and BZR1 T177A transgenic plants has suggested that the subcellular distribution of BZR1 is a primary mechanism regulating the expression of target genes in response to BR signaling. 13 this mechanism may allow plants to rapidly respond to environmental or developmental stimuli without de novo synthesis of these important transcription factors. In addition, our study also strongly suggested that BZR1 itself acts as a cytosolic signaling mediator to transmit BR signals to the nucleus.…”

Section: Spatial Redistribution Of Key Transcriptional Regulators In mentioning

confidence: 99%

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Spatial redistribution of key transcriptional regulators in brassinosteroid signaling

Ryu¹,

Kim

Hwang

2008

Plant Signaling & Behavior

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Brassinosteroids (BRs) are steroid phytohormones required for plant growth and development. The perception of BRs at the plasma membrane initiates intracellular signaling and induces dephosphorylation of two key transcription factors, BZR1 and BZR2/BES1. Phosphorylation of these factors is modulated by the GSK3 kinase BIN2 and phosphatase BSU1 and, in turn, controls DNA binding, protein stabilization, or/and nuclear translocation of BZR1 and BZR2/BES1. However, cytosolic signaling events and the biological roles of phosphorylation in BR signaling are still largely unknown. Recently, we demonstrated that BZR1 itself acts as a cytosolic signaling mediator and regulates expression of BR-responsive genes via phosphorylation-mediated nucleocytoplasmic shuttling. BIN2-mediated phosphorylation mediates nuclear export of BZR1 via interaction with a 14-3-3 protein, while BR activated phosphatases induce nuclear import of BZR1. The temporal and spatial expression of BIN2 appears to be essential in BR signaling. In this addendum, we summarize new findings in BR signaling and discuss the possibility that light and brassinosteroid signals intersect at BIN2 expression.Brassinosteroids (BRs), a group of steroid phytohormones, are essential for plant growth and for developmental processes such as seed germination, stem elongation, vascular differentiation, photomorphogenesis, and stress responses. 1-4 BR initiates its signaling cascade through a plasma membrane-associated receptor kinase complex composed of BRI1 (BRaSSInoSteRoId InSenSItIVe 1) and BaK1 (BRI1 aSSoCIated ReCePtoR KInaSe1). [5][6][7] BR signals perceived at the membrane are transmitted to the nucleus and activate at least two key transcriptional regulators, BZR1 (BRaSSInaZoLe ReSIStant1) and BZR2/ BeS1 (BRaSSInaZoLe ReSIStant2/ BRI1-eMS-SUPPReSSoR 1) via dephosphorylation. 8,9 the phosphorylation status of the two transcriptional regulators is tightly regulated by the activity of the BIn2 kinase and BSU1 (BRI1 SUPPReSSoR1) phosphatase, and is currently regarded as the most reliable readout in BR signaling. [10][11][12] However, lack of accurate information on the mechanism of action and subcellular localization of each signaling component hinders understanding of the precise biological roles of phosphorylation events in BR signaling.Phosphorylation of BZR1 and BZR2/BeS1 may be involved in the protein stabilization, nuclear accumulation of these two factors, as well as their interaction with targeted dna cis-elements. In a recent issue of Plant Cell, 13 we clearly showed that phosphorylation of BZR1 plays a key role in dynamic shuttling of BZR1 between the cytoplasm and the nucleus. BR-activated phosphatases dephosphorylate BZR1 and induce rapid nuclear localization. In the absence of BR signaling, BIn2-mediated phosphorylation events increase nuclear export of BZR1 through an interaction with 14-3-3 proteins. In this study, we identified two functional domains including 10 serine/threonine residues together which have regulatory roles in BIn2-mediated phosphorylat...

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“…Since the bin2-1 mutant carrying E263K mutation was isolated as a BR-insensitive mutant (Choe et al, 2002;Li and Nam, 2002;Perez-Perez et al, 2002), genetic and biochemical analyses have illustrated that BIN2, a GSK3-like kinase, negatively regulates BR-responsive transcription factors, BZR1 and BZR2, leading to the inhibition of plant growth when BR levels are low. BIN2 phosphorylation of BZR1/2 causes the inhibition of BZR1/2 activity through multiple mechanisms such as cytoplasmic retention mediated by 14-3-3 protein, loss of DNA binding activity, and degradation by 26S proteasome (Gampala et al, 2007;He et al, 2002;Ryu et al, 2007;Vert and Chory, 2006;Zhao et al, 2002). Of ten GSK3-like kinases in Arabidopsis, recent studies suggest that seven members including BIN2 are involved in BR signaling (Kim et al, 2009;Rozhon et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Structural and Functional Characterization of Arabidopsis GSK3-like Kinase AtSK12

Youn

Kim

et al. 2013

Molecules and Cells

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Plant GSK3-like kinases are key regulators that modulate a broad range of physiological processes such as cell growth, stomatal and flower development, responses for abiotic and biotic stress, and carbohydrate metabolism. Arabidopsis Shaggy/GSK3-like kinases (AtSK) consist of ten members that are classified into four subfamilies (I~IV). Only one of these Arabidopsis GSK3s, BIN2 (also named AtSK21), has been characterized by biochemical and genetic studies. BIN2 acts as a negative regulator in brassinosteroid (BR) signaling that controls cell growth and differentiation. Recent studies suggest that at least seven AtSKs are involved in BR signaling. However, specificities for the substrates and the functional differences of each member of the family remain to be determined. Here we report structural characteristics and distinct function of AtSK12 compared with BIN2. AtSK12 has a longer N-terminal extension, which is absent in BIN2. Transgenic plants overexpressing the AtSK12 mutant carrying deletion of Nterminal region display more severe dwarf phenotypes than those of the wild-type AtSK12. Microscopic analysis reveals that N-terminal-deleted AtSK12 accumulates in the nucleus. This implies that structural difference in the Nterminal region of AtSK members contributes to their subcellular localization. In contrast to BIN2, overexpression of AtSK12 does not cause a stomatal cluster. Furthermore, we show that YODA MAPKKK, which controls stomatal development, interacts with BIN2 but not with AtSK12. Our results suggest that AtSK12 mediates BR-regulated cell growth but not stomatal development while BIN2 regulates both processes. Our study provides evidence that different GSK3 members can have overlapping but non-identical functions.

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Nucleocytoplasmic Shuttling of BZR1 Mediated by Phosphorylation Is Essential inArabidopsisBrassinosteroid Signaling

Cited by 299 publications

References 46 publications

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF–TDR signalling

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF–TDR signalling

Spatial redistribution of key transcriptional regulators in brassinosteroid signaling

Structural and Functional Characterization of Arabidopsis GSK3-like Kinase AtSK12

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