BACKGROUND Hox genes are expressed in specific domains along the anterior posterior body axis and define the regional identity. In most animals these genes are organized in a single cluster in the genome and the order of the genes in the cluster is correlated with the anterior to posterior expression of the genes in the embryo. The conserved order of the various Hox gene orthologs in the cluster among most bilaterians implies that such a Hox cluster was present in their last common ancestor. Vertebrates are the only metazoans so far that have been shown to contain duplicated Hox clusters, while all other bilaterians seem to possess only a single cluster. RESULTS We here show that at least three Hox genes of the spider Cupiennius salei are present as two copies in this spider. In addition to the previously described duplicated Ultrabithorax gene, we here present sequence and expression data of a second Deformed gene, and of two Sex comb reduced genes. In addition, we describe the sequence and expression of the Cupiennius proboscipedia gene. The spider Cupiennius salei is the first chelicerate for which orthologs of all ten classes of arthropod Hox genes have been described. The posterior expression boundary of all anterior Hox genes is at the tagma border of the prosoma and opisthosoma, while the posterior boundary of the posterior Hox genes is at the posterior end of the embryo. CONCLUSION The presence of at least three duplicated Hox genes points to a major duplication event in the lineage to this spider, perhaps even of the complete Hox cluster as has taken place in the lineage to the vertebrates. The combined data of all Cupiennius Hox genes reveal the existence of two distinct posterior expression boundaries that correspond to morphological tagmata boundaries.

中文翻译：

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蜘蛛Cupiennius salei中的Hox基因重复。

背景技术Hox基因在前体后轴的特定区域表达并定义区域同一性。在大多数动物中，这些基因被组织在基因组中的单个簇中，并且簇中基因的顺序与基因在胚胎中的前后表达相关。大多数双语者中簇中各种Hox基因直系同源物的保守顺序暗示着这种Hox簇存在于他们的最后共同祖先中。迄今为止，脊椎动物是唯一的后生动物，它们具有重复的Hox簇，而所有其他的双语者似乎只拥有一个簇。结果我们在这里显示蜘蛛Cupiennius salei的至少三个Hox基因作为两个副本存在于该蜘蛛中。除了先前描述的重复的Ultrabithorax基因外，我们在这里提供了第二个“变形”基因和两个“性梳”还原基因的序列和表达数据。此外，我们描述了Cupiennius proboscipedia基因的序列和表达。蜘蛛Cupiennius salei是第一个被描述为所有十种节肢动物Hox基因直系同源物的螯合物。所有前Hox基因的后表达边界在前，后角膜的标签边界，而后Hox基因的后边界在胚胎的后末端。结论至少三个重复的Hox基因的存在表明该蜘蛛谱系中有一个主要的复制事件，甚至可能是脊椎动物谱系中完整的Hox簇。