Light-regulated modification and nuclear translocation of cytosolic G-box binding factors in parsley.
Functional cell-free systems may be excellent tools with which to investigate light-dependent signal transduction mechanisms in plants. By evacuolation of parsley protoplasts and subsequent silicon oil gradient centrifugation of lysed evacuolated protoplasts, we obtained a highly pure and concentrated plasma membrane-containing cytosol. Using GT- and G-box DNA elements, we were able to demonstrate a specific localization of a pool of G-box binding activity and factors (GBFs) but not one of GT-box binding activity in this cytosolic fraction. The DNA binding activity of the cytosolic GBFs is modulated in vivo as well as in vitro by light and phosphorylation/dephosphorylation activities. The regulation of cytosolic G-box binding activity by irradiation with continuous white light and phosphorylation correlates with a light-modulated transport of GBFs to the nucleus. This was shown by a GBF-antibody cotranslocation assay in permeabilized, cell-free evacuolated parsley protoplasts. We propose that a light-regulated subcellular displacement of cytosolic GBFs to the nucleus may be an important step in the signal transduction pathway coupling photoreception to light-dependent gene expression.
Harter
K
K
Department of Biology II, University of Freiburg, Germany.
Kircher
S
S
Frohnmeyer
H
H
Krenz
M
M
Nagy
F
F
Schäfer
E
E
D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000528:radiation effects; D051790:G-Box Binding Factors; D008027:Light; D019684:Magnoliopsida / Q000378:metabolism* / Q000528:radiation effects; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000378:metabolism; D010766:Phosphorylation; D011523:Protoplasts / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism* / Q000528:radiation effects; D013379:Substrate Specificity; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D051790:G-Box Binding Factors; D015345:Oligonucleotide Probes; D012097:Repressor Proteins; D014157:Transcription Factors; D004247:DNA