The Drosophila apterous 56f mutation impairs circadian locomotor activity

Abstract

We investigated effects of apterous mutation ap^56f on circadian locomotor activity, eclosion rhythms, and transcript levels of period and timeless in Drosophila. We investigated circadian locomotor activity and eclosion rhythms in ap ^56fand wild-type flies, their F1 and F2 offspring, and wingless vestigial mutants and show that ap ^56f disrupts circadian locomotor rhythms in a genetically recessive manner, that is not caused by the absence of wings. The ap ^blt strain also showed impaired circadian activity rhythms, providing independent evidence for a significant role of apterous in circadian locomotor rhythm expression. The ap ^56f mutation did not disrupt a circadian eclosion rhythm or rhythmic expression of the period and timeless clock genes, indicating that apterous is not essential for circadian clock function, but is necessary for coupling locomotor activity to a circadian clock. Timeless transcription was reduced in ap ^56f flies in 12:12 LD, suggesting that apterous may modulate core clock gene expression.

Keywords: Drosophila; apterous; circadian; eclosion; gene expression; locomotor activity.

Figure 1.

Actogram depicting activity pattern of a typical CS+ fly with over 48 hours shown on the x-axis and successive days on the y-axis for 4 days in a light-dark cycle (12:12 LD) followed by five days of constant dark (DD).

Figure 2.

Composite actograms for experiment 1. The ap^56f strain shows weak circadian rhythmicity in LD and DD, compared to robust rhythms for the CS+ wild-type strain and a wingless vg¹ mutant strain.

Figure 3.

Composite actograms for experiment 2. F1 hybrids between CS+ wild-type and ap^56f strains display circadian rhythms in LD and DD similar to wild-type parents, demonstrating that the ap^56f circadian phenotype is recessive.

Figure 4.

Composite actograms for experiment 3. F2W flies with wild-type wing phenotypes display circadian activity rhythms similar to wild-type flies (CS+), but F2A flies with ap^56f phenotypes display weak circadian rhythmicity similar to the ap^56f parent strain, demonstrating that the weak circadian activity trait segregates with the ap^56f wing phenotype.

Figure 5.

Composite actograms for experiment four comparing ap^56f and ap^blt effects on circadian activity rhythms. Both apterous alleles show lower amplitude circadian activity rhythm expression than wild-type flies.

Figure 6.

Composite actograms of eclosion data from experiment five. (A) CS+ in LD; (B) CS+ in DD; (C) ap^56f in LD and (D) ap^56f in DD. Both wild type (CS) and ap^56f flies were significantly rhythmic in LD and DD, and ap^56f flies showed a significantly stronger rhythmicity and wild-type in both conditions.

Figure 7.

Changes in transcription from the period and timeless loci between ZT6 andZT12 in ap^56f versus wild-type flies. Both wild-type (CS) and apterous show robust (significant) increases in per and tim transcripts at ZT12 vs. ZT6.

Figure 8.

Transcription from the period and timeless loci in ap^56f versus wild-type flies at ZT6 and ZT12. ap^56f flies show a reduction in per (trending) and tim (significant) transcripts at ZT12 compared to wild-type (CS).