The molecular mechanisms underlying local adaptation to high elevation habitats in the honey bee Apis mellifera

理解进化过程和驱动种群间表型分化的分子基础是当前生物学的主要问题之一。染色体重排，如倒位，可以与壮观的表型，适应的重要后果提供了基础。然而，功能数据来验证这一假设是稀疏的。在东非，蜜蜂Apis mellifera的种群生活在山地森林中（表示为A.m. monticola），在行为（即觅食生态和侵略）和形态上与居住在周围低地稀树草原的蜜蜂明显不同（A. M. scutellata）。先前发现的两条染色体上的染色体倒位在高地和低地人群之间的不同单倍型上发生频率很高，而在其他方面则是低分化的染色体。在拟议的项目中，我们将获得全基因组核苷酸多态性沿着海拔梯度的蜜蜂在六个非洲山区系统。这些数据将确定祖先倒位的分布，并将破译在杂交和环境条件的影响下，当地人群中的突变动态。转录组分析将识别与高海拔栖息地和适应性多态性相关的遗传分化、倒置基因组区域内外的调控模块。此外，我们将使用CRISPR/Cas9方法来了解所选候选基因在适应海拔中的作用。一组候选基因参与控制行为（章鱼胺受体，建议在耐热性和侵略性中发挥作用），位于其中一个倒置区域内。易位实验将证明基因型组成，基因表达和适应海拔之间的功能关系。为了确定温度相关的觅食活动中的章鱼胺能通路的作用，我们将跟踪个人蜜蜂觅食使用射频识别（RFID）和链接觅食行为的温度和章鱼胺受体的表达。此外，我们将测试如果操作的章鱼胺能系统将影响温度相关的飞行行为沿着海拔梯度。基因敲除和行为学实验将有助于分离攻击性和耐热性候选基因的功能。使用高度互补的方法，我们将因此获得全面的见解蜜蜂适应海拔的遗传结构。我们的研究将进一步有助于理解倒位和共适应等位基因对个体适应度的功能后果。

Understanding the evolutionary processes and the molecular basis that have driven the phenotypic differentiation among populations is one of the major current questions in biology. Chromosomal rearrangements such as inversions can be linked to spectacular phenotypes, providing the basis for important consequences of adaptation. However, functional data to validate this hypothesis are sparse. In East Africa, populations of the honey bee Apis mellifera live in the mountain forest (denoted as A.m. monticola) and clearly differ in behavior (i.e. foraging ecology and aggression) and morphology from those inhabiting the surrounding lowland savannahs (A. m. scutellata). Chromosomal inversions on two chromosomes identified previously have shifted to high frequency on different haplotypes of otherwise lowly differentiated chromosomes between highland and lowland populations. In the proposed project we will obtain genome-wide nucleotide polymorphisms along elevational gradients of honey bees in six African mountain systems. These data will determine the distribution of the ancestral inversions and will decipher the dynamics of mutations among local populations under the influence of hybridization and environmental conditions. Transcriptome analyses will identify regulatory modules within and outside the genetic differentiated, inverted genomic regions linked to high elevation habitats and adaptive polymorphism. Further, we will use the CRISPR/Cas9 method to understand the role of selected candidate genes in adaptation to elevation. One group of the candidate genes are involved in the control of behavior (octopamine ß receptors, suggested function in thermotolerance and aggression) that are located within one of the inverted regions. Translocation experiments will demonstrate functional relationships between genotype composition, gene expression and adaptation to elevation. To identify the role of the octopaminergic pathway in temperature-related foraging activity we will track individual honey bee foragers using radio frequency identification (RFID) and link foraging behavior to temperature and octopamine receptor expression. Further, we will test if manipulation of the octopaminergic system will affect temperature-related flight behavior along elevational gradients. Gene knockout and behavioral experiments will help to dissociate functions of individual candidate genes in aggression and thermotolerance. Using highly complementary approaches we will thus gain comprehensive insights into the genetic architecture of adaptation to elevation in honey bees. Our study will further contribute to the understanding of functional consequences of inversions and co-adapted alleles on individual fitness.