Genetic and developmental origins of a unique foraging adaptation in a Lake Malawi cichlid genus
Genetic and developmental origins of a unique foraging adaptation in a Lake Malawi cichlid genus
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DOI：
10.1073/pnas.1719798115
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发表时间：
2018-07-03
影响因子：
11.1
通讯作者：
Albertson, R. Craig
中科院分区：
文献类型：
--
作者：
Conith, Moira R.;Hu, Yinan;Albertson, R. Craig
表型新颖性是形态多样性的一个重要但知之甚少的类别。它们可以提供对表型变异起源的见解，但我们对它们的遗传起源知之甚少。慈鲷鱼显示显着的多样性颅面解剖，包括几个新奇。这种变化的一个方面是一个明显的，夸张的吻，已经演变成一个单一的马拉维慈鲷血统，并与觅食专业化和增加生态成功。我们研究了这种表型的发育和遗传起源，发现吻部由两个肥大的组织组成：颌间韧带（IML），连接上颌的左右两侧，以及覆盖的疏松结缔组织。IML存在于所有慈鲷科，但在其夸张的形式，它与更浅的结缔组织和锚定上皮交错，形成一个独特的韧带上皮复合体。我们研究了转化生长因子β（TGF β）->巩膜轴（Scx）候选途径，并证实了这些因子在吻部发育中的作用。我们进一步证明，TGF β的实验性上调足以产生scx表达的扩展和伴随的吻部形态的变化。遗传和基因组作图表明，典型的TGF β信号转导的核心成员与吻部变异的数量性状位点（QTL）分离。这些数据也暗示了韧带发育的候选者adam 12，我们使用斑马鱼模型证实了这一点。总的来说，这些数据提供了对韧带形态发生的见解，以及如何在分子水平上产生生态相关的新奇。
Phenotypic novelties are an important but poorly understood category of morphological diversity. They can provide insights into the origins of phenotypic variation, but we know relatively little about their genetic origins. Cichlid fishes display remarkable diversity in craniofacial anatomy, including several novelties. One aspect of this variation is a conspicuous, exaggerated snout that has evolved in a single Malawi cichlid lineage and is associated with foraging specialization and increased ecological success. We examined the developmental and genetic origins for this phenotype and found that the snout is composed of two hypertrophied tissues: the intermaxillary ligament (IML), which connects the right and left sides of the upper jaw, and the overlying loose connective tissue. The IML is present in all cichlids, but in its exaggerated form it interdigitates with the more superficial connective tissue and anchors to the epithelium, forming a unique ligament-epithelial complex. We examined the Transforming growth factor beta (Tgf beta) -> Scleraxis (Scx) candidate pathway and confirmed a role for these factors in snout development. We demonstrate further that experimental up-regulation of Tgf beta is sufficient to produce an expansion of scx expression and concomitant changes in snout morphology. Genetic and genomic mapping show that core members of canonical Tgf beta signaling segregate with quantitative trait loci (QTL) for snout variation. These data also implicate a candidate for ligament development, adam12, which we confirm using the zebrafish model. Collectively, these data provide insights into ligament morphogenesis, as well as how an ecologically relevant novelty can arise at the molecular level.