Collaborative Research Proposal: Tipping the Scales - A selection approach to the developmental regulation of morphological scaling

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。身体各部分的比例是动物身体形态的典型特征。在物种内部，器官需要与身体保持正确的比例，才能使有机体发挥作用；较大的个体需要更大的心脏、更长的四肢等，而较小的个体通常由比例较小的部分组成。虽然一个物种内的相对器官大小或多或少是恒定的，但不同物种的相对器官大小可能会有很大差异；事实上，身体各部分的相对大小的变化通常是物种之间最显著的生理差异。例如，长颈鹿通过夸大脖子和四肢相对于身体的大小来形成独特而优雅的身体，而海象则通过缩小四肢相对于巨大身体的大小来获得健壮而紧凑的外表。尽管描述了无数物种的身体比例已经有近一个世纪的研究，但关于如何保持比例以保持物种内的身体形态，或者如何修改以改变物种之间的身体形态，人们知之甚少。最近的方法从数学上模拟了从第一原理到尺度关系的表达和演化。这些模型侧重于调节和整合个体身体部位生长的生理过程，并确定控制相对身体部位大小的特定发育机制。重要的是，这些模型可以用来确定这些机制的哪些方面可能会改变，从而造成物种之间的身体比例差异。这项研究项目将使用三步法来测试这些模型的有效性和预测能力。首先，人工选择将被用来独立改变果蝇的翅膀和身体之间的比例关系。其次，将利用人工选择产生的苍蝇来探索影响翅膀和身体大小之间比例关系的生理机制。第三，将确定导致相对机翼大小变化的特定基因。该研究计划首次测试了基于生理和遗传的比例关系调节和进化的数学模型。它承诺回答长期存在的问题，即如何保持伸缩以保持物种内部的形态，或者如何随着物种之间的身体形态多样化而进行修改。此外，该项目将为休斯顿大学和密歇根州立大学的本科生和研究生提供广泛的跨校园培训。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)The scaling of body parts is the quintessential feature of animal body form. Within species, organs need to be correctly proportioned to the body for the organism to function; larger individuals require larger hearts, longer limbs, etc., whereas smaller individuals generally are composed of proportionally smaller parts. While relative organ size is more or less constant within a species, it can vary dramatically among species; in fact, changes in the relative size of body parts are typically the most pronounced physical difference between species. For example, giraffes derive their distinctive, gracile body form from exaggeration in the size of their necks and limbs relative to their bodies, whereas walrus gain their robust, compact appearance from reduction in the size of their limbs relative to their massive bodies. Despite nearly a century of work describing the body proportions of myriad species, little is known about how scaling is maintained to preserve body form within a species or is modified to alter body form between species. Recent approaches model mathematically the expression and evolution of scaling relationships from first principles. These models focus on the physiological processes that regulate and integrate the growth of individual body parts and identify the specific developmental mechanisms that underlie the control of relative body part size. Importantly, the models can be used to identify which aspects of these mechanisms are likely to change to create differences in body proportions among species This research project will test the validity and predictive power of these models using a three-step approach. First, artificial selection will be used to independently alter the scaling relationship between the wing and body in the fly, Drosophila melanogaster. Second, the physiological mechanisms affecting the scaling relationship between wing and body size will be explored using the flies created through artificial selection. Third, the specific genes responsible for changes in relative wing size will be identified.This research program is the first to test physiological and genetic-based mathematical models of the regulation and evolution of scaling relationships. It promises to answer long-standing questions of how scaling is maintained to preserve form within species or is modified as body form diversifies between species. In addition, the project will provide extensive, cross-campus training for undergraduate and graduate students at the University of Houston and Michigan State University.