CAREER: Discovering the Developmental Genetic Basis for Parallel Evolution of Aerial Respiration in Arthropods

从水到陆地的运动对脊椎动物和节肢动物(昆虫、蜘蛛、千足类、甲壳类等)来说都是一个关键的进化转变。不同的节肢动物群体使用不同的方法来呼吸空气，这是陆地上生命的关键要求，这种变化至少在7个群体中分别发生。这个项目的目标是研究呼吸空气的呼吸系统是如何在多个节肢动物群体中独立进化的。空气呼吸的进化是否涉及改变每个节肢动物群体中相同的解剖结构和基因，或者每个节肢动物群体使用不同的解决方案来呼吸空气？为了解决这个问题，我们将研究8种节肢动物呼吸器官的胚胎形成。将对基因和蛋白质进行测试，以确定是否所有节肢动物的呼吸系统都使用了相同的基因。基因组测序将进一步测试和识别创造独特呼吸结构的基因(例如蜘蛛的书肺)。这项研究的结果将被整合到一门新的以实验室为基础的无脊椎动物动物学课程中，该课程每年通过动物系使用活标本进行教学。博物馆将利用化石、基因和发育生物学的证据，开发一项关于节肢动物在陆地上移动的展览。一名博士后、一名研究生和十名暑期本科生将在工作期间接受培训，重点是招募女性和科学界代表性较低的群体。节肢动物空气呼吸的平行进化研究以前仅限于对几个分类群的功能形态或表达数据的研究。一些发育数据表明，下颌和海龟的呼吸系统是直接同源的，而另一组数据表明，蜘蛛类的呼吸器官独立于修改后的行走腿而产生。在发育遗传学的背景下，多足类的呼吸系统还没有被研究过。为了解决节肢动物内化呼吸系统的起源，拟议的工作将检查八个新兴模式节肢动物系统中呼吸器官的位置、遗传和序列同源性。为了建立蜘蛛类呼吸器官的序列同源性，将进行HOX错误表达实验，以降低后节附属物的压力。为了确定节肢动物间管状发生的基因调控网络(GRN)的保守性程度，将对建立果蝇黑腹果蝇气管小管系统所需的候选基因进行基因表达分析。为了评估功能的一致性，将在两个螯齿样本和三个下颌样本中对Drosphila GRN中的五个关键基因进行敲除实验。为了研究蜘蛛类书本肺的模式，将从蜘蛛和蝎子的书本肺原基中产生比较转录数据，以确定一组可能参与书本肺形态发生的新候选基因，以便进一步功能筛选。这项工作将使用位置、序列和遗传同源性的独立测试，直接解决节肢动物陆系化的两个相互竞争的场景，这两个场景持续存在于文献中。

The movement from water to land was a critical evolutionary transformation for both vertebrates and arthropods (insects, spiders, millipedes, crustaceans, etc.). Different groups of arthropods used different methods to enable breathing air, a critical requirement for life on land, a change that occurred separately in at least 7 groups. The goal of this project is to investigate how an air-breathing respiratory system evolved separately in multiple arthropod groups. Did evolution of aerial respiration involve alteration to the same anatomical structures and genes in each group, or does each arthropod group use a different solution to the problem of breathing air? To resolve this question, the embryonic formation of respiratory organs in eight arthropod species will be investigated. Genes and proteins will be tested to determine whether the same genes are used in the respiratory system of all arthropods. Genome sequencing will further test and identify genes that create unique respiratory structures (e.g., the book lung of spiders). The outcomes of this research will be integrated into a new laboratory-based course on invertebrate zoology, to be taught annually through the Department of Zoology, using live specimens. A museum exhibit will be developed on the movement of arthropods onto land, and using evidence from fossils, genes, and developmental biology. One postdoctoral fellow, one graduate student, and ten summer undergraduates will be trained during the work, emphasizing recruitment of women and underrepresented groups in science.Investigating the parallel evolution of aerial respiration in Arthropoda has previously been limited to studies of functional morphology or expression data from a few taxa. Some developmental data suggest that mandibulate and chelicerate respiratory systems are directly homologous, whereas a separate set of data suggests that respiratory organs of arachnids arose independently from modified walking legs. Respiratory systems of Myriapoda have not been studied in a developmental genetic context at all. To resolve the origins of internalized respiratory systems of arthropods, the proposed work will examine positional, genetic, and serial homology of respiratory organs in eight emerging model arthropod systems. To establish the serial homology of arachnid respiratory organs, Hox misexpression experiments will be conducted to derepress appendages in posterior segments. To establish degree of conservation of the gene regulatory network (GRN) underlying tubulogenesis across Arthropoda, gene expression assays will be performed for candidate genes known to be required for establishment of the Drosophila melanogaster tracheal tubule system. To assess functional correspondence, knockdown experiments will be conducted in two chelicerate and three mandibulate exemplars for five critical genes in the Drosphila GRN. To investigate the patterning of the arachnid book lung, comparative transcriptomic data will be generated from book lung primordia of spiders and scorpions, toward identifying a set of novel candidate genes putatively involved in book lung morphogenesis for further functional screening. This work will directly address the two competing scenarios of arthropod terrestrialization that persist in the literature, using independent tests of positional, serial, and genetic homology.