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Transcription factor HAT 1 is phosphorylated by BIN 2 kinase and mediates brassinosteroid repressed gene expression in A rabidopsis
Author(s) -
Zhang Dawei,
Ye Huaxun,
Guo Hongqing,
Johnson Abbagail,
Zhang Meishan,
Lin Honghui,
Yin Yanhai
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12368
Subject(s) - brassinosteroid , gene , microbiology and biotechnology , chemistry , biology , genetics , arabidopsis , mutant
Summary Plant steroid hormones, brassinosteroids ( BR s), play essential roles in modulating cell elongation, vascular differentiation, senescence and stress responses. BR s signal through plasma membrane‐localized receptor and other components to modulate the BES 1/ BZR 1 ( BRI 1‐ 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 (Ch IP ) experiments as a direct target gene of BES 1. Loss‐of‐function and gain‐of‐function mutants of HAT 1 display altered BR responses. HAT 1 and its close homolog HAT 3 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 HAT 1 and HAT 3 function to activate BR ‐mediated growth. Expression levels of several BR ‐repressed genes are increased in hat1 hat3 and reduced in HAT 1 OX , suggesting that HAT 1 functions to repress the expression of a subset of BR target genes. HAT 1 and BES 1 bind to a conserved homeodomain binding (HB) site and BR response element (BRRE) respectively, in the promoters of some BR ‐repressed genes. BES 1 and HAT 1 interact with each other and cooperate to inhibit BR ‐repressed gene expression. Furthermore, HAT 1 can be phosphorylated and stabilized by GSK 3 ( GLYCOGEN SYNTHASE KINASE 3)‐like kinase BIN 2 ( 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.

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