The maize Dof protein PBF activates transcription of gamma-zein during maize seed development.
Maize PBF (prolamin-box binding factor) belongs to the Dof class of plant specific transcription factors containing one highly conserved zinc finger DNA-binding domain, called Dof (DNA binding with one finger) domain. Maize PBF trans-activates the gamma-zein gene (gammaZ) promoter in developing maize seeds as shown by transient expression in maize endosperms. Co-transfection of a gammaZ:GUS construct with 35S:PBF resulted in a sevenfold increase in GUS expression, however, PBF mutation in Cys residues within the Dof domain abolishes both, binding to DNA and the capacity to activate gammaZ promoter. We present two pieces of evidence that PBF transactivates gammaZ promoter by binding to the Pb3 motif (TGTAAAG). First, recombinant Dof domain of PBF (bdPBF) specifically recognized Pb3 site as shown by gel mobility shift assays and second, co-expression of PBF with gammaZ promoter mutated in Pb3 motif suppressed PBF trans-activation capacity. Immunocytochemical analysis on developing endosperm sections shows that PBF is localized in the nuclei of the peripheral layer cells of starchy endosperm, the tissue in which the initial accumulation of gamma-zein protein occurs. By contrast, PBF is detected in the cytosol of the starchy endosperm cells newly differentiated from aleurone daughter cells, where gamma-zein was absent. Taken together these data indicate that maize PBF plays an essential role in the regulation of the temporal and spatial expression of gammaZ gene.
Marzábal
Pau
P
Consorci CSIC-IRTA, Jordi Girona 18-26, 08034 Barcelona, Spain.
Gas
Elisabet
E
Fontanet
Pilar
P
Vicente-Carbajosa
Jesús
J
Torrent
Margarita
M
Ludevid
M Dolores
MD
D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000502:physiology*; D024202:Electrophoretic Mobility Shift Assay; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D010940:Plant Proteins / Q000502:physiology*; D012639:Seeds / Q000235:genetics / Q000254:growth & development*; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*; D003313:Zea mays / Q000196:embryology* / Q000235:genetics; D015028:Zein / Q000235:genetics*
D017931:DNA Primers; D004268:DNA-Binding Proteins; C115836:PBF protein, plant; D010940:Plant Proteins; D014157:Transcription Factors; D015028:Zein