Evolution of gene expression and gene regulation during head development in Drosophila americana and D. novamexicana

了解地球上观察到的形态多样性的分子基础是生物学研究的一个主要目标。成体形态的自然变异是发育过程变化的结果，发育过程受发育基因产物的作用调节。进化发育生物学（Evo-Devo）的研究表明，发育基因表达的变异是表型多样性的主要驱动因素。虽然已经揭示了相当简单的形态性状变异的遗传变化，但复杂性状进化的遗传和发育基础在很大程度上仍然难以捉摸。由于昆虫头部是一个由主要感觉器官组成的复杂结构，它是一个很好的模型来回答这个问题。近年来，我们和其他人表明，在果蝇中，成年头形和眼睛大小的自然变异是普遍存在的。基于我们之前广泛的形态学和遗传学数据，我提出了两个主要目标。首先，我将把与美洲鬣蜥和新美洲鬣蜥头部形状和眼睛大小差异相关的遗传变异与全基因组发育基因表达（RNAseq）和基因调控（ATACseq）的变异联系起来。该分析将为未来的功能验证实验提供高可信度的候选基因。染色体倒位是一种特殊类型的遗传变异，与表型多样性有关。不同的倒位分布在美洲蓟马种群中，有些倒位分布在新美洲蓟马种群中。因此，第二个目标是将反转的存在与发育基因的调节和表达变化联系起来。这样的数据将允许检验一些常见的假设，解释为什么逆行现象在人群中出现频率上升。最终，我们的数据将有助于更好地理解反转如何影响表型多样性的机制。

Understanding the molecular basis of the morphological diversity observed on earth is a major aim of biological research. Natural variation in adult morphology is the result of changes in developmental processes, which are regulated by the action of developmental gene products. Research in evolutionary developmental (Evo-Devo) biology established that variation in developmental gene expression is a major driver of phenotypic diversity. While genetic changes underlying variation in rather simple morphological traits have been revealed, the genetic and developmental basis of complex trait evolution remains largely elusive. Since the insect head is a complex structure comprising major sensory organs it is an excellent model to contribute answers to this question. In recent years, we and others showed that natural variation in adult head shape and eye size is pervasive in Drosophila. Building on our extensive prior morphological and genetic data, I propose two main objectives. First, I will link genetic variants associated with differences in head shape and eye size between D. americana and D. novamexicana to variation in genome wide developmental gene expression (RNAseq) and gene regulation (ATACseq). This analysis will allow revealing high confidence candidate genes for future functional validation experiments. Chromosomal inversions are a special type of genetic variation that has been associated with phenotypic diversity. Various inversions segregate among D. americana populations and some of them are shared with D. novamexicana. Therefore, the second objective is to link the presence of inversions to variation in regulation and expression of developmental genes. Such data will allow testing common hypotheses explaining why inversions raise in frequency in a population. Eventually our data will contribute to a better mechanistic understanding of how inversions impact phenotypic diversity.