Pegoraro Mirko, Flavell Laura M M, Menegazzi Pamela, Colombi Perrine, Dao Pauline, Helfrich-Förster Charlotte, Tauber Eran
Department of Genetics and Genome Biology, University of Leicester, University Road, Leicester, LE1 7RH, UK.
School of Natural Science and Psychology, Liverpool John Moores University, Liverpool, L3 3AF, UK.
BMC Genomics. 2020 Aug 31;21(1):596. doi: 10.1186/s12864-020-07020-z.
Most animals restrict their activity to a specific part of the day, being diurnal, nocturnal or crepuscular. The genetic basis underlying diurnal preference is largely unknown. Under laboratory conditions, Drosophila melanogaster is crepuscular, showing a bi-modal activity profile. However, a survey of strains derived from wild populations indicated that high variability among individuals exists, including flies that are nocturnal.
Using a highly diverse population, we performed an artificial selection experiment, selecting flies with extreme diurnal or nocturnal preference. After 10 generations, we obtained highly diurnal and nocturnal strains. We used whole-genome expression analysis to identify differentially expressed genes in diurnal, nocturnal and crepuscular (control) flies. Other than one circadian clock gene (pdp1), most differentially expressed genes were associated with either clock output (pdf, to) or input (Rh3, Rh2, msn). This finding was congruent with behavioural experiments indicating that both light masking and the circadian pacemaker are involved in driving nocturnality.
Our study demonstrates that genetic variation segregating in wild populations contributes to substantial variation in diurnal preference. We identified candidate genes associated with diurnality/nocturnality, while data emerging from our expression analysis and behavioural experiments suggest that both clock and clock-independent pathways are involved in shaping diurnal preference. The diurnal and nocturnal selection strains provide us with a unique opportunity to understand the genetic architecture of diurnal preference.
大多数动物将其活动限制在一天中的特定时段，分为昼行性、夜行性或晨昏性。昼行偏好的遗传基础在很大程度上尚不清楚。在实验室条件下，黑腹果蝇是晨昏性的，表现出双峰活动模式。然而，一项对野生种群衍生菌株的调查表明，个体之间存在高度变异性，包括夜行性的果蝇。
我们使用高度多样化的种群进行了一项人工选择实验，选择具有极端昼行或夜行偏好的果蝇。经过10代后，我们获得了高度昼行和夜行的菌株。我们使用全基因组表达分析来鉴定昼行、夜行和晨昏性（对照）果蝇中差异表达的基因。除了一个生物钟基因（pdp1）外，大多数差异表达基因与生物钟输出（pdf、to）或输入（Rh3、Rh2、msn）相关。这一发现与行为实验一致，表明光掩蔽和生物钟起搏器都参与驱动夜行性。
我们的研究表明，野生种群中分离的遗传变异导致了昼行偏好的显著差异。我们鉴定了与昼行性/夜行性相关的候选基因，而我们的表达分析和行为实验得出的数据表明，生物钟和非生物钟途径都参与了塑造昼行偏好。昼行和夜行选择菌株为我们提供了一个独特的机会来了解昼行偏好的遗传结构。
