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，这主要通过两种方式实现，即细胞大小和细胞数量的变化。最近的研究发现，在线虫、昆虫和哺乳动物等多种生物中，有许多基因影响细胞大小。然而，关于器官和细胞大小调节的物种差异的遗传基础，以及这如何导致器官形态上的特异性变化，人们知之甚少。我们拟研究两种近缘昆虫的雄翅细胞大小差异。一种雄性（N. vitripennis）有小的退化前翼，而在密切相关的物种（N. giraulti）中，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。翅膀细胞的大小可以从遗传学上进行研究，因为这些物种是相互干扰的，允许基因在它们之间移动。在初步研究中，我们介绍了从giraulti到vitripenia的5个主要影响翅膀大小的区域。一个区域（wsl）占翅膀大小差异的40%，主要是由于细胞大小的增加。一秒（wdw）可以在不增加翼长的情况下使机翼宽度增加30%；细胞的大小增加，特别是在翅膀的中间部分。第三种（sww）缩短了机翼长度，增加了宽度，使ww/wl比提高了11%。这些基因中的每一个都以孟德尔的方式分离，因此代表一个或一组紧密相连的基因座。它们还代表了其他细胞大小调节研究中未描述的独特表型。使用连锁可见和致死标记，我们已经将wsl周围的渗入区域的大小减少到基因组的0.5%以下，约1.7Mb。我们还绘制了几个胰岛素信号基因，其中两个（例如s6k和tor）与翅膀大小差异相关的位点密切相关。

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.