Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA.
Sci Rep. 2019 Nov 1;9(1):15849. doi: 10.1038/s41598-019-52312-4.
Tree swallows (Tachycineta bicolor) are one of the most commonly studied wild birds in North America. They have advanced numerous research areas, including life history, physiology, and organismal responses to global change; however, transcriptomic resources are scarce. To further advance the utility of this system for biologists across disciplines, we generated a transcriptome for the tree swallow using six tissues (brain, blood, ovary, spleen, liver, and muscle) collected from breeding females. We de novo assembled 207,739 transcripts, which we aligned to 14,717 high confidence protein-coding genes. We then characterized each tissue with regard to its unique genes and processes and applied this transcriptome to two fundamental questions in evolutionary biology and endocrinology. First, we analyzed 3,015 single-copy orthologs and identified 46 genes under positive selection in the tree swallow lineage, including those with putative links to adaptations in this species. Second, we analyzed tissue-specific expression patterns of genes involved in sex steroidogenesis and processing. Enzymes capable of synthesizing these behaviorally relevant hormones were largely limited to the ovary, whereas steroid binding genes were found in nearly all other tissues, highlighting the potential for local regulation of sex steroid-mediated traits. These analyses provide new insights into potential sources of phenotypic variation in a free-living female bird and advance our understanding of fundamental questions in evolutionary and organismal biology.
树燕（Tachycineta bicolor）是北美的研究最为广泛的野生鸟类之一。它们涉及了多个研究领域，包括生活史、生理学和生物体对全球变化的反应；然而，转录组资源却很匮乏。为了进一步推进该系统在跨学科生物学家中的应用，我们从繁殖期的雌性个体中采集了 6 种组织（脑、血、卵巢、脾、肝和肌肉），用于构建树燕的转录组。我们从头组装了 207,739 条转录本，并将其比对到 14,717 个高可信度的蛋白质编码基因。然后，我们根据每种组织的独特基因和功能进行了特征描述，并将该转录组应用于进化生物学和内分泌学中的两个基本问题。首先，我们分析了 3,015 个单拷贝直系同源基因，并在树燕谱系中鉴定出 46 个受到正选择的基因，其中包括那些与该物种适应相关的基因。其次，我们分析了参与性类固醇生成和加工的基因的组织特异性表达模式。能够合成这些行为相关激素的酶主要局限于卵巢，而类固醇结合基因则存在于几乎所有其他组织中，这突显了局部调节性类固醇介导特征的潜力。这些分析为自由生活的雌性鸟类的表型变异提供了新的见解，并推进了我们对进化和机体生物学基本问题的理解。
