Circadian plasticity evolves through regulatory changes in a neuropeptide gene.

Area of Science:

• Evolutionary biology
• Chronobiology
• Genetics

Background:

• Circadian plasticity, the ability to adjust daily activity patterns to light cycles, is common in many organisms.
• The evolution of this trait and its genetic basis remain poorly understood.
• Drosophila melanogaster exhibits circadian plasticity, while the specialist Drosophila sechellia has lost this ability.

Purpose of the Study:

• To investigate the genetic mechanisms underlying the evolution of circadian plasticity.
• To compare the neuropeptide pigment-dispersing factor (Pdf) gene's role in circadian plasticity between Drosophila melanogaster and Drosophila sechellia.

Main Methods:

• Comparative analysis of Drosophila melanogaster and Drosophila sechellia.
• Screening of circadian mutants in interspecies hybrids.
• RNA interference and rescue experiments in Drosophila melanogaster.
• Analysis of cis-regulatory divergence and selection signals in the Pdf gene.

Main Results:

• The neuropeptide pigment-dispersing factor (Pdf) gene contributes to the loss of circadian plasticity in Drosophila sechellia.
• Species-specific temporal expression of Pdf, driven by cis-regulatory divergence, influences behavioral plasticity.
• The Pdf regulatory region shows signs of selection in both species, correlating with latitude and specialization.
• Circadian plasticity provides a selective advantage for Drosophila melanogaster at higher latitudes.

Conclusions:

• The Pdf gene is a key locus for the evolution of circadian plasticity.
• Divergence in Pdf regulation has shaped the distribution and specialization of Drosophila species.
• Understanding Pdf's role sheds light on adaptation to different light environments and speciation.