Pavangadkar, Kanchan , Thomashow, Michael , Triezenberg, Steven .
Function of Coactivator Proteins ADA2 and GCN5 in Cold Acclimation in Arabidopsis.
Covalent modifications of histones are important in regulating eukaryotic transcription. Lysine acetylation within the N-terminal tails of histones is associated with transcriptionally active genes and is catalyzed by histone acetyltransferases (HAT). GCN5 (a HAT) and ADA2 are components of coactivator complexes such as SAGA in yeast. The Arabidopsis genome encodes one homologue of GCN5 and two homologues of ADA2 (ADA2a and ADA2b). Null mutants of GCN5 and ADA2b have pleiotropic effects on plant growth and development whereas ada2a mutants show no aberrant phenotype.
Cold acclimation is the process by which plants increase their freezing tolerance upon exposure to low non-freezing temperatures. Arabidopsis ADA2 and GCN5 can physically interact with the transcriptional activator CBF1, which binds to and activates the expression of cold-regulated (COR) genes during cold acclimation. ada2b and gcn5 mutants show a delay in activation and a reduction in expression of COR genes during cold acclimation. Chromatin immunoprecipitation (ChIP) assays showed that acetylation of histone H3 at the COR promoters increases upon cold acclimation. Plants overexpressing wildtype CBF1 showed increased H3 acetylation at COR gene promoters even without cold stress; a CBF mutant lacking the activation domain did not. Thus, CBF is sufficient to elicit an increase in H3 acetylation at the COR gene promoters. We hypothesized that CBF recruits GCN5 and ADA2b to acetylate histones at COR gene promoters and thus help activate COR genes. However, ada2b and gcn5 mutants showed histone acetylation levels similar to wild type plants upon cold acclimation. Thus, ADA2b and GCN5 are not essential for cold-induced H3 acetylation at COR gene promoters.
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1 - Michigan State University, Biochemistry and Molecular Biology, 310 Plant Biology, Michigan State University, East Lansing, MI, 48824, USA
2 - Michigan State University, DOE-Plant Research Laboratory
3 - Van Andel Institute, Van Andel Institute Graduate School
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM