title: Transcriptional repression by AtMYB4 controls production of UV-protecting sunscreens in Arabidopsis.
abstract: An Arabidopsis thaliana line that is mutant for the R2R3 MYB gene, AtMYB4, shows enhanced levels of sinapate esters in its leaves. The mutant line is more tolerant of UV-B irradiation than wild type. The increase in sinapate ester accumulation in the mutant is associated with an enhanced expression of the gene encoding cinnamate 4-hydroxylase, which appears to be the principal target of AtMYB4 and an effective rate limiting step in the synthesis of sinapate ester sunscreens. AtMYB4 expression is downregulated by exposure to UV-B light, indicating that derepression is an important mechanism for acclimation to UV-B in A.thaliana. The response of target genes to AtMYB4 repression is dose dependent, a feature that operates under physiological conditions to reinforce the silencing effect of AtMYB4 at high activity. AtMYB4 works as a repressor of target gene expression and includes a repression domain. It belongs to a novel group of plant R2R3 MYB proteins involved in transcriptional silencing. The balance between MYB activators and repressors on common target promoters may provide extra flexibility in transcriptional control.
authors.affiliation: John Innes Centre, Colney, Norwich NR4 7UH, Institute of Food Research, Colney, Norwich NR4 7UH, UK.
authors.forename: H
authors.initials: H
authors.lastname: Jin
authors.forename: E
authors.initials: E
authors.lastname: Cominelli
authors.forename: P
authors.initials: P
authors.lastname: Bailey
authors.forename: A
authors.initials: A
authors.lastname: Parr
authors.forename: F
authors.initials: F
authors.lastname: Mehrtens
authors.forename: J
authors.initials: J
authors.lastname: Jones
authors.forename: C
authors.initials: C
authors.lastname: Tonelli
authors.forename: B
authors.initials: B
authors.lastname: Weisshaar
authors.forename: C
authors.initials: C
authors.lastname: Martin
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D017353:Gene Deletion; D015870:Gene Expression; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011837:Radiation-Protective Agents / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014466:Ultraviolet Rays
chemical_list: D010940:Plant Proteins; D011837:Radiation-Protective Agents; D012097:Repressor Proteins