Evolutionary origin and genomic organisation of runt-domain containing genes in arthropods.
Evolutionary origin and genomic organisation of runt-domain containing genes in arthropods.
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DOI：
10.1186/1471-2164-9-558
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发表时间：
2008-11-25
期刊：
影响因子：
4.4
通讯作者：
Dearden PK
中科院分区：
文献类型：
--
作者：
Duncan EJ;Wilson MJ;Smith JM;Dearden PK
基因簇，如Hox基因簇，已知在发育中具有关键作用。在真核生物中，基因簇主要由串联基因复制和分化产生。簇内的基因通常是共调节的，提供选择压力以维持基因组组织，并且这种共调节可以导致基因表达的时间或空间共线性。先前已经注意到，在果蝇中，四个含有runt-domain（RD）的基因中的三个被发现在1号染色体上的一个相对紧密的簇中，提高了在果蝇中推定的功能RD基因簇的可能性。黑腹菌为了研究这种基因簇的可能性，在几种内翅昆虫、两种外翅昆虫和两种非昆虫节肢动物中鉴定了黑腹果蝇RD基因的直系同源物。在所有的昆虫物种中，确定了四个RD基因，并通过系统发育分析将其分配给果蝇序列。虽然在甲壳动物D. pulex的同源性不能归属于昆虫序列，表明在六足动物谱系从甲壳动物谱系分裂之后，来自单一祖先的独立基因重复。在昆虫中，观察到这些基因的两种染色体排列;第一种是半分散的簇，例如在果蝇中，菱形与三个RD基因的核心簇通常由DNA的兆碱基分开。第二种排列是四个RD基因的紧密簇，例如在意大利蜜蜂中。这种基因组组织，特别是三个核心RD基因，提出了共享的调控元件的可能性。用原位杂交技术研究了四种RD基因在果蝇和蜜蜂胚胎中的表达。在胚胎发生过程中，没有证据表明表达的空间或时间共线性。所有完全测序的昆虫基因组都包含四个RD基因，并且可以基于与D.黑腹蛋白序列。这些基因的基因组组织检查提供了一个功能性RD基因簇的证据。来自非昆虫节肢动物的RD基因也成簇，然而这些和昆虫RD基因之间缺乏直系同源性表明该簇可能是由独立于产生昆虫RD基因簇的重复事件引起的。两种翅内目昆虫胚胎RD基因的表达分析mellifera和D.因此，尽管该基因簇的功能意义仍然未知，但其在昆虫进化过程中的维持暗示了该基因簇的某些功能意义。
Gene clusters, such as the Hox gene cluster, are known to have critical roles in development. In eukaryotes gene clusters arise primarily by tandem gene duplication and divergence. Genes within a cluster are often co-regulated, providing selective pressure to maintain the genome organisation, and this co-regulation can result in temporal or spatial co-linearity of gene expression. It has been previously noted that in Drosophila melanogaster, three of the four runt-domain (RD) containing genes are found in a relatively tight cluster on chromosome 1, raising the possibility of a putative functional RD gene cluster in D. melanogaster. To investigate the possibility of such a gene cluster, orthologues of the Drosophila melanogaster RD genes were identified in several endopterygotan insects, two exopterygotan insects and two non-insect arthropods. In all insect species four RD genes were identified and orthology was assigned to the Drosophila sequences by phylogenetic analyses. Although four RD genes were found in the crustacean D. pulex, orthology could not be assigned to the insect sequences, indicating independent gene duplications from a single ancestor following the split of the hexapod lineage from the crustacean lineage. In insects, two chromosomal arrangements of these genes was observed; the first a semi-dispersed cluster, such as in Drosophila, where lozenge is separated from the core cluster of three RD genes often by megabases of DNA. The second arrangement was a tight cluster of the four RD genes, such as in Apis mellifera. This genomic organisation, particularly of the three core RD genes, raises the possibility of shared regulatory elements. In situ hybridisation of embryonic expression of the four RD genes in Drosophila melanogaster and the honeybee A. mellifera shows no evidence for either spatial or temporal co-linearity of expression during embryogenesis. All fully sequenced insect genomes contain four RD genes and orthology can be assigned to these genes based on similarity to the D. melanogaster protein sequences. Examination of the genomic organisation of these genes provides evidence for a functional RD gene cluster. RD genes from non-insect arthropods are also clustered, however the lack of orthology between these and insect RD genes suggests this cluster is likely to have resulted from a duplication event independent from that which created the insect RD gene cluster. Analysis of embryonic RD gene expression in two endopterygotan insects, A. mellifera and D. melanogaster, did not show evidence for coordinated gene expression, therefore while the functional significance of this gene cluster remains unknown its maintenance during insect evolution implies some functional significance to the cluster.
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