Zhao Xiaqing, Bergland Alan O, Behrman Emily L, Gregory Brian D, Petrov Dmitri A, Schmidt Paul S
Department of Biology, University of Pennsylvania
Department of Biology, Stanford University.
Mol Biol Evol. 2016 Mar;33(3):707-20. doi: 10.1093/molbev/msv263. Epub 2015 Nov 13.
Wild populations of the model organism Drosophila melanogaster experience highly heterogeneous environments over broad geographical ranges as well as over seasonal and annual timescales. Diapause is a primary adaptation to environmental heterogeneity, and in D. melanogaster the propensity to enter diapause varies predictably with latitude and season. Here we performed global transcriptomic profiling of naturally occurring variation in diapause expression elicited by short day photoperiod and moderately low temperature in two tissue types associated with neuroendocrine and endocrine signaling, heads, and ovaries. We show that diapause in D. melanogaster is an actively regulated phenotype at the transcriptional level, suggesting that diapause is not a simple physiological or reproductive quiescence. Differentially expressed genes and pathways are highly distinct in heads and ovaries, demonstrating that the diapause response is not uniform throughout the soma and suggesting that it may be comprised of functional modules associated with specific tissues. Genes downregulated in heads of diapausing flies are significantly enriched for clinally varying single nucleotide polymorphism (SNPs) and seasonally oscillating SNPs, consistent with the hypothesis that diapause is a driving phenotype of climatic adaptation. We also show that chromosome location-based coregulation of gene expression is present in the transcriptional regulation of diapause. Taken together, these results demonstrate that diapause is a complex phenotype actively regulated in multiple tissues, and support the hypothesis that natural variation in diapause propensity underlies adaptation to spatially and temporally varying selective pressures.
模式生物黑腹果蝇的野生种群在广阔的地理范围内以及季节和年度时间尺度上经历高度异质的环境。滞育是对环境异质性的一种主要适应方式，在黑腹果蝇中，进入滞育的倾向随纬度和季节而可预测地变化。在这里，我们对与神经内分泌和内分泌信号相关的两种组织类型（头部和卵巢）中由短日照光周期和适度低温引发的滞育表达的自然变异进行了全球转录组分析。我们表明，黑腹果蝇的滞育在转录水平上是一种受积极调控的表型，这表明滞育不是一种简单的生理或生殖静止状态。头部和卵巢中差异表达的基因和途径高度不同，这表明滞育反应在整个躯体中并不一致，并表明它可能由与特定组织相关的功能模块组成。在滞育果蝇头部下调的基因显著富集了与地理渐变单核苷酸多态性（SNP）和季节性振荡SNP，这与滞育是气候适应的驱动表型这一假设一致。我们还表明，基于染色体位置的基因表达共调控存在于滞育的转录调控中。综上所述，这些结果表明滞育是一种在多个组织中受到积极调控的复杂表型，并支持滞育倾向的自然变异是对空间和时间变化的选择压力适应基础这一假设。
