Bulla gouldiana period exhibits unique regulation at the mRNA and protein levels.
The authors cloned the period (per) gene from the marine mollusk Bulla gouldiana, a well-characterized circadian model system. This allowed them to examine the characteristics of the per gene in a new phylum, and to make comparisons with the conserved PER domains previously characterized in insects and vertebrates. Only one copy of the per gene is present in the Bulla genome, and it is most similar to PER in two insects: the cockroach, Periplaneta americana, and silkmoth, Antheraea pernyi. Comparison with Drosophila PER (dPER) and murine PER 1 (mPER1) sequence reveals that there is greater sequence homology between Bulla PER (bPER) and dPER in the regions of dPER shown to be important to heterodimerization between dPER and Drosophila timeless. Although the structure suggests conservation between dPER and bPER, expression patterns differ. In all cells and tissues examined that are peripheral to the clock neurons in Bulla, bPer mRNA and protein are expressed constitutively in light:dark (LD) cycles. In the identified clock neurons, the basal retinal neurons (BRNs), a rhythm in bPer expression could be detected in LD cycles with a peak at zeitgeber time (ZT) 5 and trough expression at ZT 13. This temporal profile of expression more closely resembles that of mPER1 than that of dPER. bPer rhythms in the BRNs were not detected in continuous darkness. These analyses suggest that clock genes may be uniquely regulated in different circadian systems, but lead to similar control of rhythms at the cellular, tissue, and organismal levels.
Constance
Cara M
CM
National Science Foundation Center for Biological Timing, Department of Biology, University of Virginia, Charlottesville 22903-2477, USA.
Green
Carla B
CB
Tei
Hajime
H
Block
Gene D
GD
D000818:Animals; D015139:Blotting, Southern; D002940:Circadian Rhythm / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D029721:Drosophila Proteins; D005123:Eye; D017952:Ganglia, Invertebrate / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D007422:Intestines / Q000502:physiology; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D012333:RNA, Messenger