ADP-Dependent Phosphorylation Regulates Association of a
DNA-Binding Complex with the Barley Chloroplast psbD
Blue-Light-Responsive Promoter1
Minkyun Kim,
David A. Christopher, and
John E. Mullet*
Department of Biochemistry and Biophysics, Crop Biotechnology
Center, Texas A&M University, College Station, Texas 77843 (M.K.,
J.E.M.); Department of Molecular Biosciences and Biosystems
Engineering, University of Hawaii at Manoa, St. John 503, Honolulu,
Hawaii 96822 (D.A.C.); and Department of Agricultural Chemistry,
Division of Applied Biology and Chemistry, College of Agriculture and
Life Sciences, Seoul National University, Suwon 441-744, Republic of
Korea (M.K.)
The chloroplast gene
psbD encodes D2, a chlorophyll-binding protein located
in the photosystem II reaction center. Transcription of
psbD in higher plants involves at least three promoters,
one of which is regulated by blue light. The psbD
blue-light-regulated promoter (BLRP) consists of a 
10 promoter
element and an activating complex, AGF, that binds immediately upstream
of 35. A second sequence-specific DNA-binding complex, PGTF, binds
upstream of AGF between 71 and 100 in the barley (Hordeum
vulgare) psbD BLRP. In this study we report that
ADP-dependent phosphorylation selectively inhibits the binding of PGTF
to the barley psbD BLRP. ATP at high concentrations
(1-5 mM) inhibits PGTF binding, but in the presence of
phosphocreatine and phosphocreatine kinase, this capacity is lost,
presumably due to scavenging of ADP. ADP inhibits PGTF binding at
relatively low concentrations (0.1 mM), whereas other
nucleotides are unable to mediate this response. ADP-mediated
inhibition of PGTF binding is reduced in the presence of the protein
kinase inhibitor K252a. This and other results suggest that
ADP-dependent phosphorylation of PGTF (or some associated protein)
inhibits binding of PGTF to the psbD BLRP and reduces transcription. ADP-dependent phosphorylation is expected to increase in
darkness in parallel with the rise in ADP levels in chloroplasts. ADP-dependent phosphorylation in chloroplasts may, therefore, in
coordination, inactivate enzymes involved in carbon assimilation, protein synthesis, and transcription during diurnal light/dark cycles.
1
This research was supported by the National
Institutes of Health (grant no. GM 37987 to J.E.M.) and by the Texas
Agricultural Experiment Station.
*
Corresponding author; jmullet{at}tamu.edu; fax
1-409-862-4718.
Plant Physiol. (1999) 119: 663-670
Copyright Clearance Center: 0032-0889/99/119//08
© 1999 American Society of Plant Physiologists
