Involvement of a nuclear-encoded basic helix-loop-helix protein in transcription of the light-responsive promoter of psbD.
In the chloroplast psbD light-responsive promoter (LRP), a highly conserved sequence exists upstream from the bacterial -10/-35 elements. Multiple sequence-specific DNA binding proteins are predicted to bind to the conserved sequence as transcription factors. Using yeast one-hybrid screening of an Arabidopsis cDNA library, a possible DNA binding protein of the psbD LRP upstream sequence was identified. The protein, designated PTF1, is a novel protein of 355 amino acids (estimated molecular weight of 39.6) that contains a basic helix-loop-helix DNA binding motif in the predicted N-terminal region of the mature protein. Transient expression assay of PTF1-GFP fusion protein showed that PTF1 was localized in chloroplasts. Using the modified DNA sequence in the one-hybrid system, the ACC repeat was shown to be essential for PTF1 binding. The rate of psbD LRP mRNA accumulation was reduced in a T-DNA-inserted Arabidopsis ptf1 mutant. Compared with wild-type plants, the mutant had pale green cotyledons and its growth was inhibited under short-day conditions. These results suggest that PTF1 is a trans-acting factor of the psbD LRP.
Baba
K
K
RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan. kyoko.baba@genfys.slu.se
Nakano
T
T
Yamagishi
K
K
Yoshida
S
S
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D002467:Cell Nucleus / Q000502:physiology*; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics; D018257:Helix-Loop-Helix Motifs; D008027:Light; D008969:Molecular Sequence Data; D016296:Mutagenesis; D045332:Photosystem II Protein Complex / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics* / Q000528:radiation effects; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D029681:Arabidopsis Proteins; D017931:DNA Primers; D045332:Photosystem II Protein Complex; C479885:PsbD protein, Arabidopsis