Functional Conservation of Clock Output Signaling between Flies and Intertidal Crabs

Gene duplication in crabs has resulted in two pigment-dispersing hormone genes, β-pdh-I and β-pdh-II.

• β-pdh-I is more closely related to the insect pigment-dispersing factor than β-pdh-II.
• Expression of β-PDH-I in the crab's brain resembles that of the clock output signal PDF in fruit flies.
• Neurons expressing β-PDH-I show similar immunoreactivity patterns as seen with clock-related proteins in other species.
• β-PDH-I can rescue arrhythmic behavior in fruit fly mutants, while β-PDH-II does not restore normal rhythms.
• Both PDF and β-PDH-I activate the signal transduction pathway of the PDF receptor, unlike β-PDH-II.

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