Meeting Abstract
66.2 Wednesday, Jan. 6 Circadian oscillations in gene expression in the sea anemone Nematostella vectensis: the evolution of the animal circadian clock REITZEL, AM; BEHRENDT, L; TARRANT, AM*; Woods Hole Oceanographic Inst.; WHOI; WHOI atarrant@whoi.edu
Circadian clocks provide biochemical cues for diurnal variations in physiology and behavior. In animals, circadian clocks are generally entrained by oscillations in light that are detected by photoreceptive cryptochromes. This leads to variable expression and degradation of a suite of genes, including several members of the bHLH-PAS family. Circadian regulators in the bHLH-PAS family affect gene expression by binding to conserved E-box sequences in the promoters of target genes. While many circadian regulatory genes are deeply conserved, the signaling pathways differ among animal lineages. Characterizing circadian regulation in a cnidarian provides insight into the origins of animal circadian rhythms and into regulation of environmentally cued behaviors, such as gametogenesis and spawning. We have identified homologs of circadian regulatory genes in the sea anemone Nematostella vectensis, including five cryptochromes, a suite of genes involved in phosphorylation and proteosomal degradation, and homologs of clock, timeless and cycle. We maintained Nematostella either in complete darkness or in a 12 hour light: 12 hour dark cycle and measured expression of cryptochromes, kinases, timeless, and bHLH-PAS genes. Gene expression varied in response to light cycle, with a particularly strong pattern observed for the clock homolog. We predict that clock signaling is mediated through dimerization with bmal/cycle and binding of the heterodimers to E-boxes. We have identified E-box sequences in the promoters of two genes (clock, one cryptochrome), both of which showed strong transcriptional cycling, further supporting a hypothesis that these elements are important for regulating gene expression . Experiments are in progress to characterize dimerization patterns among Nematostella bHLH-PAS proteins and their interactions with E-boxes and natural promoter sequences
