An essential role for 14-3-3 proteins in brassinosteroid signal transduction in Arabidopsis.
Brassinosteroids (BRs) are essential hormones for plant growth and development. BRs regulate gene expression by inducing dephosphorylation of two key transcription factors, BZR1 and BZR2/BES1, through a signal transduction pathway that involves cell-surface receptors (BRI1 and BAK1) and a GSK3 kinase (BIN2). How BR-regulated phosphorylation controls the activities of BZR1/BZR2 is not fully understood. Here, we show that BIN2-catalyzed phosphorylation of BZR1/BZR2 not only inhibits DNA binding, but also promotes binding to the 14-3-3 proteins. Mutations of a BIN2-phosphorylation site in BZR1 abolish 14-3-3 binding and lead to increased nuclear localization of BZR1 protein and enhanced BR responses in transgenic plants. Further, BR deficiency increases cytoplasmic localization, and BR treatment induces rapid nuclear localization of BZR1/BZR2. Thus, 14-3-3 binding is required for efficient inhibition of phosphorylated BR transcription factors, largely through cytoplasmic retention. This study demonstrates that multiple mechanisms are required for BR regulation of gene expression and plant growth.
Department of Plant Biology, Carnegie Institution, Stanford, CA 94305, USA.
Srinivas S
SS
Gampala
Tae-Wuk
TW
Kim
Jun-Xian
JX
He
Wenqiang
W
Tang
Zhiping
Z
Deng
Mingyi-Yi
MY
Bai
Shenheng
S
Guan
Sylvie
S
Lalonde
Ying
Y
Sun
Joshua M
JM
Gendron
Huanjing
H
Chen
Nakako
N
Shibagaki
Robert J
RJ
Ferl
David
D
Ehrhardt
Kang
K
Chong
Alma L
AL
Burlingame
Zhi-Yong
ZY
Wang
D048948:14-3-3 Proteins / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D018744:DNA, Plant / Q000378:metabolism; D004268:DNA-Binding Proteins; D015536:Down-Regulation / Q000187:drug effects; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013260:Steroids, Heterocyclic / Q000378:metabolism* / Q000494:pharmacology
D048948:14-3-3 Proteins; D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011494:Protein Kinases; D013260:Steroids, Heterocyclic; C456160:BES1 protein, Arabidopsis; C454444:BZR1 protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis