Genetics of Wing and Cell-Size Evolution in Nasonia

描述（由申请人提供）：新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。最近的研究已经揭示了许多基因影响线虫、昆虫和哺乳动物等多种生物体的细胞大小。然而，很少有人知道物种差异的遗传基础，器官和细胞大小的调节，或如何导致器官特异性的形态变化。我们建议调查雄性翅细胞大小的差异之间的两个密切相关的昆虫种属Nasonia。一个种的雄性（N. vitripennis）有小的退化的前翅，而在密切相关的物种（N.雄性的翅膀大2.3倍。这种大小差异主要是由于细胞大小的差异。翅细胞的大小可以通过遗传学来研究，因为这些物种是可交配的，允许基因在它们之间移动。在初步研究中，我们已经介绍了5个区域的主要影响翅膀的大小从长颈鹿到丽翅目。一个区域（wsl）占机翼尺寸差异的40%，主要是由于细胞尺寸的增加。第二个（wdw）导致翼宽急剧增加30%，而不增加翼长;细胞大小增加，特别是在中间部分的翅膀。第三种（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方式分离，因此代表单个基因座或一组紧密连锁的基因座。它们还代表了在其他细胞大小调节研究中未描述的独特表型。使用连锁的可见和致死标记，我们已经将wsl周围的渗入区域的大小减小到<基因组的0.5%，约1.7Mb。我们还绘制了几个胰岛素信号基因，其中两个（如s6 k，tor）的地图密切参与翅膀大小的差异位点。 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）克隆和分子表征至少两个翅膀细胞大小的基因，（3）确定这些位点如何有助于翅膀细胞大小差异的发育控制。标记和致死辅助重组将用于减少侧翼区域的大小，并定位克隆翼细胞大小的基因。使用Nasonia BAC文库和映射到翅膀大小区域内的分子标记，我们将在含有翅膀细胞大小基因座的区域内构建重叠群。这些将被用来定义在映射和定位克隆过程中的渗入区域的大小，和紧密连锁的致死将被用于翼细胞大小基因的超细尺度映射。发育研究将调查翅膀发育和mRNA丰度的模式，在发展中的翅膀成虫盘，使用已知的翅膀图案基因（如enrailed，wingless），细胞大小调节（如s6 k，tor），和基因定位克隆，以确定潜在的调控机制的翅膀细胞大小的差异。 纳索尼亚是一种新兴的模式生物，具有适合细胞和器官大小进化遗传研究的几个特征。这些包括易于处理，世代时间短，重组率高，基因组大小小，雄性单倍性，可育物种，丰富的可见和分子标记，以及翼细胞大小调节的种间差异。通过利用Nasonia系统的特殊功能，这项研究将提供有关细胞和器官大小物种差异的遗传基础的第一个信息，并可能揭示参与细胞大小调节的新基因机制。

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.