title: Dominant repression by Arabidopsis transcription factor MYB44 causes oxidative damage and hypersensitivity to abiotic stress.
abstract: In any living species, stress adaptation is closely linked with major changes of the gene expression profile. As a substrate protein of the rapidly stress-induced mitogen-activated protein kinase MPK3, Arabidopsis transcription factor MYB44 likely acts at the front line of stress-induced re-programming. We recently characterized MYB44 as phosphorylation-dependent positive regulator of salt stress signaling. Molecular events downstream of MYB44 are largely unknown. Although MYB44 binds to the MBSII element in vitro, it has no discernible effect on MBSII-driven reporter gene expression in plant co-transfection assays. This may suggest limited abundance of a synergistic co-regulator. MYB44 carries a putative transcriptional repression (Ethylene responsive element binding factor-associated Amphiphilic Repression, EAR) motif. We employed a dominant repressor strategy to gain insights into MYB44-conferred stress resistance. Overexpression of a MYB44-REP fusion markedly compromised salt and drought stress tolerance--the opposite was seen in MYB44 overexpression lines. MYB44-mediated resistance likely results from induction of tolerance-enhancing, rather than from repression of tolerance-diminishing factors. Salt stress-induced accumulation of destructive reactive oxygen species is efficiently prevented in transgenic MYB44, but accelerated in MYB44-REP lines. Furthermore, heterologous overexpression of MYB44-REP caused tissue collapse in Nicotiana. A mechanistic model of MAPK-MYB-mediated enhancement in the antioxidative capacity and stress tolerance is proposed. Genetic engineering of MYB44 variants with higher trans-activating capacity may be a means to further raise stress resistance in crops.
authors: Department of Applied Genetics and Cell Biology (DAGZ), University of Natural Resources and Applied Life Sciences (BOKU), Muthgasse 18, Vienna A-1190, Austria. helene.persak@boku.ac.at.
authors: Helene
authors: H
authors: Persak
authors: Department of Applied Genetics and Cell Biology (DAGZ), University of Natural Resources and Applied Life Sciences (BOKU), Muthgasse 18, Vienna A-1190, Austria. andrea.pitzschke@boku.ac.at.
authors: Andrea
authors: A
authors: Pitzschke
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D055864:Droughts; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D018384:Oxidative Stress / Q000235:genetics; D010641:Phenotype; D030821:Plants, Genetically Modified; D054730:Protein Interaction Domains and Motifs; D055049:Salt Tolerance / Q000235:genetics; D036226:Seedlings; D016415:Sequence Alignment; D013312:Stress, Physiological / Q000235:genetics*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D029681:Arabidopsis Proteins; C529221:At5g67300 protein, Arabidopsis; D015534:Trans-Activators; D014157:Transcription Factors