A key daily rhythm gene changes to control seasonal responses through a winter timing switch

The predominant isoform of the circadian clock gene timeless (tim-sc) is regulated by photoperiod and plays a key role in seasonal adaptations in Drosophila melanogaster.

• Alternative splicing of the timeless gene influences seasonal responses through the neuropeptide pigment-dispersing factor (PDF).
• The tim-sc isoform is primarily expressed in winter and is modulated by seasonal changes in light.
• tim-sc helps maintain a 'winter lock' state in physiology and behavior by altering PDF activity.
• The canonical isoform tim-l does not show regulation in response to photoperiod changes.

Simplified