The hypothesis is tested that some heat stress transcription factors (HSFs) are activated after formation of inter- or intramolecular disulfide bonds. Based on in silico analyses we identified conserved cysteinyl residues in AtHSFA8 that might function as redox sensors in plants. AtHSFA8 represents a redox-sensitive transcription factor since upon treatment of protoplasts with H2O2 YFP-labeled HSFA8 was translocated to the nucleus in a time-dependent manner. Site-directed mutagenesis of the conserved residues Cys24 and Cys269 blocked translocation of HSFA8 to the nucleus. The findings concur with a model where HSFA8 functions as redox sensing transcription factor within the stress-responsive transcriptional network.
Keywords: AtHSFA8; Cytoplasmic-nuclear shuttling; Fluorescence resonance energy transfer; Heat stress transcription factor; Reactive oxygen species; Redox-regulation.
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