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Brassinosteroids and Salicylic Acid Mutually Enhance Endogenous Content and Signaling to Show a Synergistic Effect on Pathogen Resistance in Arabidopsis thaliana
The crosstalk mechanism regulating content and signal transduction between brassinosteroids (BRs) and salicylic acid (SA) for plant defense was investigated in Arabidopsis . Compared to the wild type, an increased bacterial resistance was observed in bzr1-1D , a dominant mutant of the BR transcripti...
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Published in: | Journal of plant biology = Singmul Hakhoe chi 2023, 66(2), , pp.181-192 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The crosstalk mechanism regulating content and signal transduction between brassinosteroids (BRs) and salicylic acid (SA) for plant defense was investigated in
Arabidopsis
. Compared to the wild type, an increased bacterial resistance was observed in
bzr1-1D
, a dominant mutant of the BR transcription factor BZR1. In
bzr1-1D
, SA biosynthetic gene
ICS1
expression and endogenous SA content greatly increased upon
Pst
DC3000 infection, and the direct binding of BZR1 to the
ICS1
promoter was confirmed through EMSA and ChIP. In
bzr1-1D
where
NPR1
expression was almost absent, expression of
PR
genes was increased, and both
BZR1
and
PR5
expressions increased after SA treatment. EMSA and ChIP verified that BZR1 binds directly to the
cis
-element present in the
PR5
promoter and a pull-down assay showed that TGAs, SA transcription factors upstream of
PR
genes, interact with BZR1 at the protein level. Crude enzyme assays demonstrated that BR C-6 oxidase activity, a CYP85A1 function, greatly increased during
Pst
DC3000 infection. In the
tga1 tga4
double mutant lacking SA transcription factors TGA1 and TGA4, BR biosynthetic gene
CYP85A1
expression was significantly reduced. EMSA and ChIP confirmed that both TGA1 and TGA4 bind to the
cis
-element present in the
CYP85A1
promoter, and castasterone (CS), a bio-active BR, was significantly reduced in
tga1 tga4
. Taken together, the upregulation of
ICS1
expression by BZR1 and
CYP85A1
expression by TGA1/4 mutually enhanced endogenous level of BR and SA in
Arabidopsis
. Furthermore, TGAs and BZR1 interaction at the protein level induces SA-induced immunity through the upregulation of
PR5
expression, increasing bacterial resistance in the plant. These results explain the mutual control mechanisms of the synergistic effects BR and SA have on plant defense and confirm BR’s effect on plant defense and growth promotion in
A. thaliana
. |
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ISSN: | 1226-9239 1867-0725 |
DOI: | 10.1007/s12374-023-09390-9 |