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Transcription factor HAT1 is phosphorylated by BIN2 kinase and mediates brassinosteroid repressed gene expression in Arabidopsis

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Plant steroid hormones, brassinosteroids (BRs), play essential roles in modulating cell elongation, vascular
differentiation, senescence and stress responses. BRs signal through plasma membrane-localized receptor
and other components to modulate the BES1/BZR1 (BRI1-EMS SUPPRESSOR 1/BRASSINAZOLE RESISTANT
1) family of transcription factors that modulate thousands of target genes. Arabodopsis thaliana homeodomain-
leucine zipper protein 1 (HAT1), which encodes a homeodomain-leucine zipper (HD-Zip) class II transcription
factor, was identified through chromatin immunoprecipitation (ChIP) experiments as a direct
target gene of BES1. Loss-of-function and gain-of-function mutants of HAT1 display altered BR responses.
HAT1 and its close homolog HAT3 act redundantly, as the double mutant hat1 hat3 displayed a reduced BR
response that is stronger than the single mutants alone. Moreover, hat1 hat3 enhanced the phenotype of a
weak allele of the BR receptor mutant bri1 and suppressed the phenotype of constitutive BR response
mutant bes1-D. These results suggest that HAT1 and HAT3 function to activate BR-mediated growth.
Expression levels of several BR-repressed genes are increased in hat1 hat3 and reduced in HAT1OX, suggesting
that HAT1 functions to repress the expression of a subset of BR target genes. HAT1 and BES1 bind
to a conserved homeodomain binding (HB) site and BR response element (BRRE) respectively, in the promoters
of some BR-repressed genes. BES1 and HAT1 interact with each other and cooperate to inhibit BRrepressed
gene expression. Furthermore, HAT1 can be phosphorylated and stabilized by GSK3 (GLYCOGEN
SYNTHASE KINASE 3)-like kinase BIN2 (BRASSINOSTEROID-INSENSITIVE 2), a well established negative
regulator of the BR pathway. Our results thus revealed a previously unknown mechanism by which BR
signaling modulates BR-repressed gene expression and coordinates plant growth.

Keywords: brassinosteroids, BES1, HAT1, HAT3, transcription repression, BIN2, phosphorylation, Arabidopsis
thaliana.

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Informasi Detail

Judul Seri

The Plant Journal

No. Panggil

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Penerbit

: John Wiley & Sons, Ltd.., 2014

Deskripsi Fisik

The Plant Journal (2014) 77, 59–70

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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