Model of a possible zCry1ab regulatory circuit in the zebrafish eye. The zCry1ab mRNA level was regulated by morning, evening, light and day length signals. Based on their mRNA expression patterns (Figs. 1–3), Cry1aa/Cry2 and Cry1ba/Cry1bb were considered morning and evening oscillators, respectively. The morning signal induced the expression of zCry1ab at midnight, regardless of light and day length conditions. In addition to resetting the morning and evening clocks, the external light signal induced zCry1ab expression in the evening to form the evening peak, which may have been based on an integrated signal of light, day length and evening information. The morning and evening peaks were independent and additive. Shown on the right are schematic drawings of zCry1ab expression profiles under long-day and short-day cycles (modified from data shown in Figs. 4 and 7). Biological signal integration and regulation are represented using logic gates, with representative images of daily regulation patterns.
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