Period gene activity in four brain cells is enough for daily rhythms in fruit flies under low light

Flies with restricted gene expression in four specific neurons showed normal bimodal activity patterns under low light conditions.

• The clock gene expressing lateral neurons is essential for rhythmic locomotor activity in Drosophila.
• PDF-expressing small ventral lateral neurons are associated with morning activity, while PDF-negative neurons and dorsal lateral neurons are linked to evening activity.
• Flies with manipulated gene expression exhibited altered phase peaks of morning and evening activity under moonlight conditions.
• Two dorsal lateral neurons advanced their activity phase in response to moonlight, suggesting a role similar to morning oscillators.
• The 5th PDF-negative small lateral neuron and one dorsal lateral neuron delayed their activity phase, consistent with evening oscillators.
• Results indicate that the function of M and E oscillators may be flexible and influenced by environmental factors rather than strictly anatomical definitions.

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