Chemical Inhibition of a Subset of Arabidopsis thaliana GSK3-like Kinases Activates Brassinosteroid Signaling

Rybel, Bert De; Audenaert, Dominique; Vert, Grégory; Rozhon, Wilfried; Mayerhofer, Juliane; Peelman, Frank; Coutuer, Silvie; Denayer, Tinneke; Jansen, Leentje; Nguyen, Long; Vanhoutte, Isabelle; Beemster, Gerrit T.S.; Vleminckx, Kris; Jonak, Claudia; Chory, Joanne; Inzé, Dirk; Russinova, Eugenia; Beeckman, Tom

doi:10.1016/j.chembiol.2009.04.008

Cited by 249 publications

(293 citation statements)

References 48 publications

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“…This would suggest that PIF4 has fewer phosphorylation sites than BES1, reported to be modified by this kinase in at least 10 independent Ser/Thr residues (Ryu et al 2010). Incubation with the specific inhibitor bikinin (De Rybel et al 2009) blocked PIF4 phosphorylation as well as autophosphorylation of BIN2, confirming that labeling of this protein is mediated by the BIN2 kinase (Fig. 3C).…”

Section: Bin2 Phosphorylates Pif4 In Vitrosupporting

confidence: 56%

BR-dependent phosphorylation modulates PIF4 transcriptional activity and shapes diurnal hypocotyl growth

et al. 2014

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Signaling by the hormones brassinosteroid (BR) and gibberellin (GA) is critical to normal plant growth and development and is required for hypocotyl elongation in response to dark and elevated temperatures. Active BR signaling is essential for GA promotion of hypocotyl growth and suppresses the dwarf phenotype of GA mutants. Cross-talk between these hormones occurs downstream from the DELLAs, as GA-induced destabilization of these GA signaling repressors is not affected by BRs. Here we show that the light-regulated PIF4 (phytochromeinteracting factor 4) factor is a phosphorylation target of the BR signaling kinase BRASSINOSTEROID-INSENSITIVE 2 (BIN2), which marks this transcriptional regulator for proteasome degradation. Expression of a mutated PIF41A protein lacking a conserved BIN2 phosphorylation consensus causes a severe elongated phenotype and strongly up-regulated expression of the gene targets. However, PIF41A is not able to suppress the dwarf phenotype of the bin2-1 mutant with constitutive activation of this kinase. PIFs were shown to be required for the constitutive BR response of bes1-D and bzr1-1D mutants, these factors acting in an interdependent manner to promote cell elongation. Here, we show that bes1-D seedlings are still repressed by the inhibitor BRZ in the light and that expression of the nonphosphorylatable PIF41A protein makes this mutant fully insensitive to brassinazole (BRZ). PIF41A is preferentially stabilized at dawn, coinciding with the diurnal time of maximal growth. These results uncover a main role of BRs in antagonizing light signaling by inhibiting BIN2-mediated destabilization of the PIF4 factor. This regulation plays a prevalent role in timing hypocotyl elongation to late night, before light activation of phytochrome B (PHYB) and accumulation of DELLAs restricts PIF4 transcriptional activity.

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Section: Bin2 Phosphorylates Pif4 In Vitrosupporting

confidence: 56%

BR-dependent phosphorylation modulates PIF4 transcriptional activity and shapes diurnal hypocotyl growth

et al. 2014

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“…Consistently, bikinin, which inhibits completely the activity of all members of SKI and SKII and partly that of ATSK32 (ref. 33), caused a similar defect to that observed in the gsk3 sextuple mutant (Fig. 7c-e).…”

Section: Bin2 Interacts With Tdr Cytoplasmic Domain In Y2h Assaysupporting

confidence: 50%

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

et al. 2014

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“…Auxin and BRs are known to co-regulate light responses such as the shade avoidance response (Keller et al, 2011;Keuskamp et al, 2011). To test whether BRs and auxin interdependently regulate stomatal development, we tested the effect of NAA on stomata formation in combination with bikinin, an inhibitor of GSK3-like kinases in BR signalling (De Rybel et al, 2009). NAA and bikinin reduced the SI in the wild type and additive effects of both chemicals were evident in the tmm-1 mutant.…”

Section: Auxin Acts Independently Of Brassinosteroids To Suppress Stomentioning

confidence: 99%

Auxin represses stomatal development in dark-grown seedlings via Aux/IAA proteins

et al. 2014

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Stomatal development is tightly regulated through internal and external factors that are integrated by a complex signalling network. Light represents an external factor that strongly promotes stomata formation. Here, we show that auxin-resistant aux/iaa mutants, e.g. axr3-1, exhibit a de-repression of stomata differentiation in dark-grown seedlings. The higher stomatal index in dark-grown axr3-1 mutants when compared with the wild type is due to increased cell division in the stomatal lineage. Excessive stomata in dark-grown seedlings were also observed in mutants defective in auxin biosynthesis or auxin perception and in seedlings treated with the polar auxin transport inhibitor NPA. Consistent with these findings, exogenous auxin repressed stomata formation in light-grown seedlings. Taken together, these results indicate that auxin is a negative regulator of stomatal development in dark-grown seedlings. Epistasis analysis revealed that axr3-1 acts genetically upstream of the bHLH transcription factors SPCH, MUTE and FAMA, as well as the YDA MAP kinase cascade, but in parallel with the repressor of photomorphogenesis COP1 and the receptor-like protein TMM. The effect of exogenous auxin required the ER family of leucine-rich repeat receptor-like kinases, suggesting that auxin acts at least in part through the ER family. Expression of axr3-1 in the stomatal lineage was insufficient to alter the stomatal index, implying that cell-cell communication is necessary to mediate the effect of auxin. In summary, our results show that auxin signalling contributes to the suppression of stomatal differentiation observed in dark-grown seedlings.

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Chemical Inhibition of a Subset of Arabidopsis thaliana GSK3-like Kinases Activates Brassinosteroid Signaling

Cited by 249 publications

References 48 publications

BR-dependent phosphorylation modulates PIF4 transcriptional activity and shapes diurnal hypocotyl growth

BR-dependent phosphorylation modulates PIF4 transcriptional activity and shapes diurnal hypocotyl growth

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

Auxin represses stomatal development in dark-grown seedlings via Aux/IAA proteins

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