An Integrative Approach to the Evolutionary Assembly of Vertebrate Body Plans

脊椎动物身体计划进化组装的综合方法

• 批准号: RGPIN-2021-04327
• 负责人: Miyashita, Tetsuto
• 金额: $ 2.04万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741827
• 关键词: Integrative; Approach; Evolutionary; Assembly; Vertebrate

Animal forms - in all their diversity - represent as few as 40+ body plans. How these basic patterns originated remains a core pursuit of evolutionary biology. However, the evolution of a body plan requires non-incremental transitions and does not readily fit models of population-level processes. To fill in this gap, my recent work has documented these transitions in early vertebrates (primitive fishes) and has also yielded a promising model in zebrafish that express a major phenotypic shift as population-level fluctuations. My long-term objective is to uncover mechanisms that both constrained and facilitated phenotypic evolution in early vertebrates. With that goal, I investigate how major discrete variations: a) arise; b) become canalized; and c) increase in disparity. To do this, I focus on key components of the vertebrate body plan: oral apparatus (OA), central nervous system (CNS), and head-trunk boundary (HTB). I hypothesize that major phenotypic variation emerges from: a) canalization of reaction norms; and b) increase in functional linkages. This hypothesis generates the following predictions: 1)Plasticity mediates functional variation caused by a novel allele, shifting reaction norms of linked traits (tested in OA); 2)Reaction norms become canalized (OA); and 3)Rates of trait evolution increase in those functionally linked to the novel trait more than in the trait itself (OA, CNS, HTB). OA: I will reveal previously unknown OA repertoire in vertebrates: a) feeding in the absence of jaw movement, observed in zebrafish mutants lacking jaw joints; and b) newly reconstructed oral discs of stem lampreys that suggest a uniquely assembled suction cup. I aim to test, using the zebrafish mutants, how plastic responses to the jaw disruption (population-level fluctuations) enabled modified suction feeding, and whether this response harbors any potential to become genetically fixed. CNS: A recent discovery revealed vertebrate-like `brain' signaling centers in non-chordate outgroup (hemichordates). However, it remains unclear whether a gene network preceded structure or hidden complexity exists in the seemingly simple hemichordate nervous system. To test this, I will map neural circuitry in hemichordates. HTB: Jawed vertebrates have a complete HTB, but this transition appears saltatory in the absence of intermediate forms. I aim to identify a transitional state of HTB evolution in a sister group of jawed vertebrates. This will constrain when and how HTB structures (neck, heart, pectoral fins) evolved in a vertebrate body. Throughout this project I investigate the mechanisms, both developmental and functional, that yielded the vertebrate body plan and also govern our anatomy. The jawless mutant zebrafish offer a new path to address a long-standing question: How do major variations arise? This facilitates the next phase: our multifaceted analysis to reveal convergent functional evolution or transitional states in early vertebrates.

动物形态多种多样，仅代表 40 多种体型。这些基本模式是如何起源的仍然是进化生物学的核心追求。然而，身体计划的演变需要非增量转变，并且不容易适应人口水平过程的模型。为了填补这一空白，我最近的工作记录了早期脊椎动物（原始鱼类）的这些转变，并在斑马鱼中产生了一个有前途的模型，该模型表达了随着种群水平波动而发生的主要表型转变。我的长期目标是揭示限制和促进早期脊椎动物表型进化的机制。为了这个目标，我研究了主要的离散变化是如何：a）出现； b) 成为运河； c) 差距扩大。为此，我重点关注脊椎动物身体结构的关键组成部分：口腔器官 (OA)、中枢神经系统 (CNS) 和头躯干边界 (HTB)。我假设主要的表型变异来自：a）反应规范的渠道化； b) 增加功能联系。该假设产生以下预测：1）可塑性介导由新等位基因引起的功能变异，改变相关性状的反应规范（在 OA 中测试）； 2)反应规范变得通畅(OA)； 3）与新性状功能相关的性状进化率比性状本身（OA、CNS、HTB）增加更多。 OA：我将揭示脊椎动物中以前未知的 OA 全部功能：a）在没有颌运动的情况下进食，在缺乏颌关节的斑马鱼突变体中观察到； b）新重建的七鳃鳗口盘，表明其具有独特组装的吸盘。我的目的是使用斑马鱼突变体来测试对下颌破坏（种群水平波动）的塑性反应如何实现改良的吸食，以及这种反应是否具有基因固定的潜力。中枢神经系统：最近的一项发现揭示了非脊索动物外群（半脊索动物）中类似脊椎动物的“大脑”信号中心。然而，目前尚不清楚看似简单的半索动物神经系统中是否存在先于结构的基因网络或隐藏的复杂性。为了测试这一点，我将绘制半索动物的神经回路。 HTB：有颌脊椎动物具有完整的 HTB，但在没有中间形式的情况下，这种转变似乎是跳跃式的。我的目标是确定有颌脊椎动物姐妹群体中 HTB 进化的过渡状态。这将限制HTB结构（颈部、心脏、胸鳍）在脊椎动物体内进化的时间和方式。在整个项目中，我研究了产生脊椎动物身体计划并控制我们的解剖结构的发育和功能机制。无颌突变斑马鱼为解决一个长期存在的问题提供了一条新途径：重大变异是如何产生的？这有利于下一阶段：我们的多方面分析揭示早期脊椎动物的趋同功能进化或过渡状态。