Light-Regulated Transcription of Genes Encoding Peridinin
Chlorophyll a Proteins and the Major Intrinsic
Light-Harvesting Complex Proteins in the Dinoflagellate
Amphidinium carterae Hulburt (Dinophycae)1
Changes in Cytosine Methylation Accompany Photoadaptation
Michael R. ten Lohuis* and
David J. Miller
Department of Biochemistry and Molecular Biology, James Cook
University of North Queensland, Townsville, Queensland 4811, Australia
In the dinoflagellate
Amphidinium carterae, photoadaptation involves changes
in the transcription of genes encoding both of the major classes of
light-harvesting proteins, the peridinin chlorophyll a
proteins (PCPs) and the major
a/c-containing intrinsic light-harvesting
proteins (LHCs). PCP and LHC transcript levels were increased up to 86- and 6-fold higher, respectively, under low-light conditions relative to
cells grown at high illumination. These increases in transcript
abundance were accompanied by decreases in the extent of methylation of
CpG and CpNpG motifs within or near PCP- and LHC-coding regions.
Cytosine methylation levels in A. carterae are therefore
nonstatic and may vary with environmental conditions in a manner
suggestive of involvement in the regulation of gene expression.
However, chemically induced undermethylation was insufficient in
activating transcription, because treatment with two methylation
inhibitors had no effect on PCP mRNA or protein levels. Regulation of
gene activity through changes in DNA methylation has traditionally been
assumed to be restricted to higher eukaryotes (deuterostomes and green
plants); however, the atypically large genomes of dinoflagellates may
have generated the requirement for systems of this type in a relatively
"primitive" organism. Dinoflagellates may therefore provide a
unique perspective on the evolution of eukaryotic DNA-methylation
systems.
1
This research was supported by grants from the
Australian Research Council and a James Cook University merit research
grant. M.R.t.L. acknowledges receipt of an Australian Research Council postdoctoral fellowship.
*
Corresponding author; e-mail michael.tenlohuis{at}jcu.edu.au; fax
61-77-25-1394.
Plant Physiol. (1998) 117: 189-196
Copyright Clearance Center: 0032-0889/98/117/0189/08
© 1998 American Society of Plant Physiologists
