Karolinska Institute, Department of Laboratory Medicine, Clinical Research Center, Karolinska University Hospital, SE-14186 Huddinge, Sweden ; School of Natural Sciences, Technology and Environmental Studies, Södertörn University, SE-141 89 Huddinge, Sweden.
Department of Biology, Molecular Ecology and Evolution Laboratory, Lund University, Ecology Building, SE-22362 Lund, Sweden ; Max Planck Institute for Evolutionary Biology, AG Behavioural Genomics, August-Thienemann-Straße 2, 24306 Plön, Germany.
Mov Ecol. 2016 Feb 15;4:4. doi: 10.1186/s40462-016-0069-6. eCollection 2016.
We still have limited knowledge about the underlying genetic mechanisms that enable migrating species of birds to navigate the globe. Here we make an attempt to get insight into the genetic architecture controlling this complex innate behaviour. We contrast the gene expression profiles of two closely related songbird subspecies with divergent migratory phenotypes. In addition to comparing differences in migratory strategy we include a temporal component and contrast patterns between breeding adults and autumn migrating juvenile birds of both subspecies. The two willow warbler subspecies, Phylloscopus trochilus trochilus and P. t. acredula, are remarkably similar both in phenotype and genotype and have a narrow contact zone in central Scandinavia. Here we used a microarray gene chip representing 23,136 expressed sequence tags (ESTs) from the zebra finch Taeniopygia guttata to identify mRNA level differences in willow warbler brain tissue in relation to subspecies and season.
Out of the 22,109 EST probe sets that remained after filtering poorly binding probes, we found 11,898 (51.8 %) probe sets that could be reliably and uniquely matched to a total of 6,758 orthologous zebra finch genes. The two subspecies showed very similar levels of gene expression with less than 0.1 % of the probe sets being significantly differentially expressed. In contrast, 3,045 (13.8 %) probe sets were found to be differently regulated between samples collected from breeding adults and autumn migrating juvenile birds. The genes found to be differentially expressed between seasons appeared to be enriched for functional roles in neuronal firing and neuronal synapse formation.
Our results show that only few genes are differentially expressed between the subspecies. This suggests that the different migration strategies of the subspecies might be governed by few genes, or that the expression patterns of those genes are time-structured or tissue-specific in ways, which our approach fails to uncover. Our findings will be useful in the planning of new experiments designed to unravel the genes involved in the migratory program of birds.
我们对于能够使迁徙鸟类在全球范围内导航的潜在遗传机制仍然知之甚少。在这里，我们试图深入了解控制这种复杂先天行为的遗传结构。我们对比了两个具有不同迁徙表型的密切相关的鸣禽亚种的基因表达谱。除了比较迁徙策略的差异外，我们还包括了一个时间成分，并对比了两个亚种的繁殖期成鸟和秋季迁徙幼鸟之间的模式。两个柳莺亚种，即 Phylloscopus trochilus trochilus 和 P. t. acredula，在表型和基因型上都非常相似，并且在斯堪的纳维亚中部的接触区很狭窄。在这里，我们使用了一个微阵列基因芯片，代表了来自斑胸草雀 Taeniopygia guttata 的 23136 个表达序列标签 (EST)，以确定与亚种和季节有关的柳莺脑组织中的 mRNA 水平差异。
在过滤了结合不良的探针后，在 22109 个 EST 探针中，我们发现了 11898 个（51.8%）探针可以可靠地唯一匹配到总共 6758 个斑马雀同源基因。两个亚种的基因表达水平非常相似，不到 0.1%的探针集表现出明显的差异表达。相比之下，在从繁殖期成鸟和秋季迁徙幼鸟中采集的样本之间，有 3045 个（13.8%）探针集的表达受到调控。在季节之间差异表达的基因似乎富集了在神经元放电和神经元突触形成中的功能作用。
我们的研究结果表明，只有少数基因在亚种之间存在差异表达。这表明亚种之间不同的迁徙策略可能由少数基因控制，或者这些基因的表达模式在时间结构或组织特异性方面，我们的方法无法揭示。我们的研究结果将有助于规划新的实验，以揭示鸟类迁徙程序中涉及的基因。
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