Bicoid: A new addition to the body plan of Drosophila

描述（由申请人提供）：虽然Bicoid morphogen （Bcd）在果蝇（Dm）胚胎的前部图案形成中起着关键作用，但在双翅目之外没有发现床同源物。在这里，我们提出保守的驼背（hb）、正畸（otd）和尾侧（cad）是祖先前模式系统的关键组成部分，其功能在糖尿病患者中被床接管。我们将探讨这些基因是否可以在糖尿病患者中共同作用，在没有bcd的情况下控制轴向模式。我们还将研究这些基因在黄冠黄蜂（Nv）中，其中hb突变产生非常严重的前表型，与我们的假设一致，即hb最初是广泛控制轴向模式所必需的。Nv胚胎发生形态与Dm胚胎发生形态的相似性有助于进行比较研究。这些对Dm和Nv的研究将帮助我们理解最近进化的Bcd获得调节功能的变化。同时，我们将研究Hb的分子功能，表征其与自身和酵母双杂交筛选中鉴定的Cad的物理相互作用。我们将继续研究Hunchback作为一种形态因子，包括研究它与Bcd的协同作用，以及它的二聚化能力。由于Dm hb可能已经失去了被床接管的功能，我们将在Dm中研究Nv hb和hb基因从物种系统发育谱的模式特性。为了了解nvhb调控，将其启动子置于Dm中，以测试bed、hb、otd或cad是否控制它。利用酵母双杂交筛选，我们观察到Hb分子之间的分子相互作用。我们将研究这种二聚化的功能，并确定它是否是Hb作为抑制物的能力所必需的，而它的激活需要与Bcd（或Otd?）相互作用。目的2：我们将研究Otd作为形态形成因子的潜力，并测试是否高水平的Otd，单独或与Hb联合，可以在没有bcd的情况下塑造胚胎的前侧。我们将克隆nvotd，利用RNAi技术研究其表达模式和表型。并研究Nv hb对其的调节，或bcd， hb和otd在Din中的调节。最后，我们将在Dm中评估来自不存在床的物种的Otd蛋白的模式功能。目的3尾状是一个后部的形态原，必须通过Bcd的跨国控制或Hb和Cad蛋白之间可能的直接拮抗在前部消除。我们将研究Hb和Cad相互作用的遗传学、生物化学和机制，以及两种机制在无脊椎动物中相对贡献的演变。我们对两种模式昆虫的比较研究，利用Dm分子遗传学的力量结合Nv的独特特征，将使我们能够记录祖先的前模式系统。我们希望重建果蝇的祖先机制，从衍生的果蝇胚胎进行“去进化”，并在昆虫中恢复更一般的发育类型，在那里床可能没有出现协调前模式功能。

DESCRIPTION (provided by applicant): Although the Bicoid morphogen (Bcd) plays a pivotal role in patterning the anterior of the Drosophila (Dm) embryo, no bed homologue has been found outside Diptera. Here, we propose that the conserved hunchback (hb), orthodenticle (otd), and caudal (cad) are the key components of an ancestral anterior patterning system whose function has been taken over by bed in Dm. We will ask whether these genes can act together in Dm to control axial patterning in the absence of bcd. We will also study these genes in the wasp Nasonia vitripenis (Nv) where a mutation in hb produces a very severe anterior phenotype, consistent with our hypothesis that hb was originally necessary for extensive control of axial patterning. The morphological similarity of Nv embryogenesis to that of Dm will facilitate comparative studies. These studies in Dm and Nv will help us understand the changes underlying the acquisition of regulatory functions by the recently evolved Bcd. In parallel, we will study the molecular function of Hb, characterizing its physical interactions with itself and with Cad identified in a yeast two-hybrid screen. Aim 1 We will continue our study of Hunchback as a morphogen, including a study of its synergy with Bcd, as well as its ability to dimerize. As Dm hb might have lost functions that have been taken over by bed, we will study in Dm the patterning properties of Nv hb and of hb genes from a phylogenetic spectrum of species. To understand Nv hb regulation, its promoter will be placed in Dm to test whether bed, hb, otd or cad controls it. Using a yeast two-hybrid screen, we have observed a molecular interaction between Hb molecules. We will investigate the function of this dimerization and address whether it is required for the ability of Hb to act as a represser, while its activation requires the interaction with Bcd (or with Otd?). Aim 2 We will study the potential of Otd as a morphogen, and test whether high levels of Otd, alone or in combination with Hb, can pattern the anterior of the embryo in the absence of bcd. We will clone Nv otd, study its expression pattern and phenotype using RNAi. and study its regulation by Nv hb, or by bcd, hb and otd when placed in Din. Finally, we will assess in Dm the patterning function of Otd proteins from species where bed does not exist. Aim 3 caudal is a posterior morphogen that must be eliminated at the anterior, through transnational control by Bcd, or by a possible direct antagonism between Hb and Cad proteins. We will study the genetics, biochemistry and mechanisms of the interaction between Hb and Cad as well as the evolution of the relative contribution of the two mechanisms in invertebrates. Our comparative studies in two model insects, using the power of Dm molecular genetics combined with the unique features of Nv, will allow us to document the ancestral anterior patterning system. We hope to reconstruct in Drosophila the ancestral mechanisms, to perform a "de-evolution" from the derived fly embryo and revive the more generic type of development in insects where bed might not have appeared to coordinate anterior patterning functions.