Nucleotide Variation in Drosophila cryptochrome Is Linked to Circadian Clock Function: An Association Analysis

Area of Science:

• Genetics
• Chronobiology
• Animal Behavior

Background:

• Cryptochrome (CRY) is a vital protein regulating circadian rhythms across diverse species.
• In Drosophila, CRY functions as a circadian photoreceptor, electromagnetic field sensor, and regulator of geotaxis behavior.
• Natural genetic variations within the CRY gene have been observed, but their functional significance remained unclear.

Purpose of the Study:

• To investigate the functional role of natural polymorphisms in the Drosophila CRY gene.
• To associate specific CRY gene variations with observable traits like circadian rhythm and behavior.
• To explore the geographical distribution and adaptive significance of CRY gene haplotypes.

Main Methods:

• Generated nearly-isogenic Drosophila strains with diverse natural CRY alleles.
• Employed association mapping to link CRY genetic variation to circadian phase.
• Conducted behavioral analyses and CRISPR-mediated gene editing to validate findings.
• Analyzed geographical distribution of CRY haplotypes across European wild populations.

Main Results:

• Identified two major CRY haplogroups (All1/All2 and B1/B2) associated with circadian phase, period, activity, and sleep.
• Demonstrated that B1/B2 polymorphism affects CRY transcription and circadian phase in transgenic flies.
• Observed a geographical cline in B1/B2 indel frequency correlating with seasonal bioclimatic variables.
• Found no significant differences in circadian photosensitivity between genotypes.

Conclusions:

• Natural CRY gene variations significantly influence Drosophila circadian rhythms and behavior.
• CRY gene polymorphism is linked to local adaptation through geographical distribution.
• The study highlights the functional importance of CRY genetic diversity in circadian system adaptation.