ABI5-binding proteins (AFPs) alter transcription of ABA-induced genes via a variety of interactions with chromatin modifiers
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Overexpression of ABI5/ABF binding proteins (AFPs) results in extreme ABA resistance of seeds via multiple mechanisms repressing ABA response, including interactions with histone deacetylases and the co-repressor TOPLESS.
Several ABI5/ABF binding proteins (AFPs) inhibit ABA response, resulting in extreme ABA resistance in transgenic Arabidopsis overexpression lines, but their mechanism of action has remained obscure. By analogy to the related Novel Interactor of JAZ (NINJA) protein, it was suggested that the AFPs interact with the co-repressor TOPLESS to inhibit ABA-regulated gene expression. This study shows that the AFPs that inhibit ABA response have intrinsic repressor activity in a heterologous system, which does not depend on the domain involved in the interaction with TOPLESS. This domain is also not essential for repressing ABA response in transgenic plants, but does contribute to stronger ABA resistance. Additional interactions between some AFPs and histone deacetylase subunits were observed in yeast two-hybrid and bimolecular fluorescence assays, consistent with a more direct mechanism of AFP-mediated repression of gene expression. Chemical inhibition of histone deacetylase activity by trichostatin A suppressed AFP effects on a small fraction of the ABI5-regulated genes tested. Collectively, these results suggest that the AFPs participate in multiple mechanisms modulating ABA response, including both TOPLESS-dependent and -independent chromatin modification.
KeywordsABA-INSENSITIVE(ABI5) AFP Arabidopsis Germination Histone deacetylase Chromatin
ABI five binding protein
ABRE binding factor
GAL4 activation domain
Arabidopsis early methionine-labelled 6
Bimolecular fluorescence complementation
GAL4 binding domain
Basic leucine zipper
- EAR domain
Ethylene-responsive element binding factor-associated amphiphilic repression domain
- HDA or HDAC
Late embryogenesis abundant
Mediator of OsbZIP46 deactivation and degradation
Novel Interactor of JAZ
Responsive to ABA 18
Sin3-associated protein 18
Topless and topless-related
We thank the ABRC team at Ohio State University for efficient distribution of vectors and cDNA clones, Dr. Xinnian Dong for the yeast cell line Y122, Dr. Barry Causier for the TPL and TPR cDNAs, and Adam Protter for assistance in constructing the YFP-AFP3 fusion. This work was supported by UCSB Academic Senate Grant to RRF, Faculty Research Assistance Program funds, and National Science Foundation Grant# IOS1558011 to RRF.
RRF conceived and performed experiments, wrote the manuscript, and repeatedly applied for funding. TJL conceived and performed experiments and provided feedback. BJE and DRM performed experiments and provided feedback.
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