Jacobsson Linn, Kronhamn Jesper, Rasmuson-Lestander Asa
Department of Molecular Biology, Umeå University, Umeå, Sweden.
Mol Genet Genomics. 2009 Sep;282(3):217-31. doi: 10.1007/s00438-009-0458-2. Epub 2009 May 30.
There are two Pax6 genes in Drosophila melanogaster; eyeless (ey) and twin-of-eyeless (toy), due to a duplication, which most likely occurred in the insect lineage. They encode transcription factors important for head development. Misexpression of either toy or ey can induce formation of ectopic compound eyes. Toy regulates the ey gene by binding to an eye-specific enhancer in its second intron. However, Toy can induce ectopic eyes also in an ey( - ) background, which indicates a redundancy between the two Pax6 copies in eye formation. To elucidate to what extent these two genes are interchangeable, we first generated toy-Gal4 constructs capable of driving the Pax6 genes in a toy-specific manner. Genetic dissection of the promoter proximal region of toy identified a 1,300-bp region around the canonical transcription start that is sufficient to drive toy expression in embryonic brain and eye primorida and in larval eye-antennal discs. We find that exogenous expression of toy can partially rescue the lethality and eye phenotype caused by lethal mutations in ey and vice versa. We therefore conclude that Toy and Ey, to some extent, can substitute for each other. Nevertheless, the phenotypes of the rescued flies indicate that the two Pax6 genes are specialized to regulate defined structures of the fly head.
在黑腹果蝇中有两个Pax6基因，即无眼基因（ey）和无眼孪生基因（toy），这是由于一次复制事件导致的，该事件很可能发生在昆虫谱系中。它们编码对头部发育很重要的转录因子。toy或ey的错误表达都能诱导异位复眼的形成。Toy通过与ey基因第二个内含子中的一个眼睛特异性增强子结合来调控ey基因。然而，Toy在ey（-）背景下也能诱导异位眼的形成，这表明在眼睛形成过程中这两个Pax6拷贝之间存在冗余。为了阐明这两个基因在多大程度上可以互换，我们首先构建了能够以toy特异性方式驱动Pax6基因的toy - Gal4构建体。对toy启动子近端区域的遗传剖析确定了一个围绕典型转录起始位点的1300 bp区域，该区域足以驱动toy在胚胎脑和眼原基以及幼虫眼触角盘中表达。我们发现，toy的外源表达可以部分挽救由ey中的致死突变引起的致死性和眼睛表型，反之亦然。因此我们得出结论，Toy和Ey在一定程度上可以相互替代。然而，获救果蝇的表型表明这两个Pax6基因专门用于调控果蝇头部的特定结构。
