Genetics of Wing and Cell-Size Evolution in Nasonia

描述(申请人提供)：新的形态如何进化是生物学中的一个基本问题。大多数形态进化涉及器官大小的变化，这基本上是通过两种方式实现的，即细胞大小和细胞数量的变化。最近的研究揭示了许多影响生物体细胞大小的基因，包括线虫、昆虫和哺乳动物。然而，关于器官和细胞大小调节的物种差异的遗传基础，或者这如何导致器官特有的形态变化，人们知之甚少。我们建议调查两种近缘昆虫的雄性翅细胞大小的差异。一个物种的雄性(N.vitriennis)有较小的退化前翼，而在近亲物种(N.giraulti)中，雄性有2.3倍大的翅膀。这种大小差异主要是由于细胞大小的差异。翅膀细胞的大小可以通过遗传学来研究，因为该物种是相互干扰的，允许基因在它们之间移动。在初步研究中，我们引入了5个对翅大小有主要影响的区域。一个区域(WSL)占机翼大小差异的40%，主要是由于细胞大小的增加。第二次(WDW)在不增加机翼长度的情况下导致机翼宽度急剧增加30%；细胞尺寸特别是在机翼的内侧部分增加。三分之一(SWW)缩短了机翼长度，增加了宽度，使WW/WL比增加了11%。这些基因中的每一个都以孟德尔式的方式分离，因此代表一个或一组紧密相连的基因座。它们也代表了其他细胞大小调节研究中没有描述的独特表型。使用连锁的可见和致命标记，我们已经将WSL周围的导入区域的大小减少到基因组的0.5%，大约1.7Mb。我们还定位了几个胰岛素信号基因，其中两个(如S6K，tor)与与翅膀大小差异有关的基因密切相关。 我们的具体目标是(1)进一步确定种间翅膀大小差异的遗传基础，(2)克隆至少两个翅膀细胞大小基因并对其进行分子表征，(3)确定这些基因座如何对翅膀细胞大小差异的发育控制做出贡献。标记和致死辅助重组将被用来减少侧翼区域的大小，并定位克隆翅膀细胞大小的基因。利用Nasonia BAC文库和与翅膀大小区域相对应的分子标记，我们将在包含翅膀细胞大小基因座的区域内构建重叠群。这些基因将被用来在作图和位置克隆过程中定义导入区域的大小，紧密连锁的致死基因将被用于超精细的翅膀细胞大小基因的作图。发育研究将利用已知的翅膀模式基因(如渐变的、无翅的)、细胞大小调节基因(如S6K、tor)和通过位置克隆确定的基因来研究翅膀发育的模式和翅膀想象盘发育中的mRNA丰度，以确定翅膀细胞大小差异的潜在调控机制。 纳斯尼亚是一种新兴的模式生物，具有几个适合于细胞和器官大小进化的遗传学研究的特征。这些问题包括易于处理、世代时间短、重组率高、基因组小、雄性单倍体、可育物种间、丰富的可见和分子标记以及翅细胞大小调节的种间差异。通过利用Nasonia系统的特殊功能，这项研究将首次提供关于细胞和器官大小物种差异的遗传基础的信息，并可能揭示参与细胞大小调节的新的基因机制。

DESCRIPTION (provided by applicant): How new morphologies evolve is a fundamental question in biology. Most morphological evolution involves changes in the size of organs, which is basically achieved in two ways, by changes in cell size and cell number. Recent studies have revealed a number of genes that effect cell size in organisms as diverse as nematodes, insects and mammals. However, little is known about the genetic basis of species differences in organ and cell size regulation, or how this leads to organ specific changes in morphology. We propose to investigate differences in male wing cell size between two closely related insect species in the genus Nasonia. Males of one species (N. vitripennis) have small vestigial forewings whereas in the closely related species (N. giraulti) males have 2.3-fold larger wings. This size difference is due mostly to differences in cell size. Wing cell size can be studied genetically because the species are interfertile, allowing movement of genes between them. In preliminary studies, we have introduced 5 regions with major effects on wing size from giraulti into vitripennis. One region (wsl) accounts for 40% of the wing size difference due mainly to an increase in cell size. A second (wdw) causes a dramatic 30% increase in wing width without increasing wing length; cell size is increased specifically in the medial portion of the wing. A third (sww) shortens wing length and increases width increasing the ww/wl ratio by 11%. Each of these segregates in a Mendelian fashion and therefore represents a single locus or set of tightly linked loci. They also represent unique phenotypes not described in other studies of cell size regulation. Using linked visible and lethal markers, we have reduced the size of the introgressed region around wsl to <0.5% of the genome, approximately 1.7Mb. We have also mapped several insulin-signaling genes, two of which (e.g. s6k, tor) map closely to loci involved in the wing size differences. Our specific goals are to (1) further determine the genetic basis of the interspecies wing size differences, (2) clone and molecularly characterize at least two wing cell-size genes and (3) determine how these loci contribute to the developmental control of wing cell-size differences. Marker and lethal assisted recombination will be used to reduce the size of the flanking regions and to positionally clone wing cell-size genes. Using the Nasonia BAC library and molecular markers that map within to the wing size regions, we will construct contigs within regions containing wing cell size loci. These will be used to define the size of the introgressed regions during mapping and positional cloning, and tightly linked lethals will be used for ultra-fine scale mapping of the wing cell-size genes. Developmental studies will investigate patterns of wing development and mRNA abundance in developing wing imaginal disks, using known wing patterning genes (e.g. engrailed, wingless), cell-size regulators (e.g. s6k, tor), and genes identified by positional cloning, to determine potential regulatory mechanisms of the wing cell-size differences. Nasonia is an emerging model organism, and has several features suited for genetic studies of cell and organ size evolution. These include ease of handling, short generation time, high recombination rate, small genome size, male haploidy, inter-fertile species, abundance of visible and molecular markers, and inter-specific differences in wing cell size regulation. By taking advantage of the particular features of the Nasonia system, this study will provide the first information on the genetic basis of species differences in cell and organ size, and may reveal new gene mechanisms involved in cell-size regulation.