Stazione Zoologica Anton Dohrn, Naples, Italy.
BMC Genomics. 2009 Nov 18;10:538. doi: 10.1186/1471-2164-10-538.
Previous investigations from our laboratory were largely focused on the genome organization of vertebrates. We showed that these genomes are mosaics of isochores, megabase-size DNA sequences that are fairly homogeneous in base composition yet belong to a small number of families that cover a wide compositional spectrum. A question raised by these results concerned how far back in evolution an isochore organization of the eukaryotic genome arose.
The present investigation deals with the compositional patterns of the invertebrates for which full genome sequences, or at least scaffolds, are available. We found that (i) a mosaic of isochores is the long-range organization of all the genomes that we investigated; (ii) the isochore families from the invertebrate genomes matched the corresponding families of vertebrates in GC levels; (iii) the relative amounts of isochore families were remarkably different for different genomes, except for those from phylogenetically close species, such as the Drosophilids.
This work demonstrates not only that an isochore organization is present in all metazoan genomes analyzed that included Nematodes, Arthropods among Protostomia, Echinoderms and Chordates among Deuterostomia, but also that the isochore families of invertebrates share GC levels with the corresponding families of vertebrates.
我们实验室之前的研究主要集中在脊椎动物的基因组组织上。我们表明，这些基因组是同调子的镶嵌物，是大小为兆碱基的 DNA 序列，在碱基组成上相当均匀，但属于少数几个家族，涵盖了广泛的组成谱。这些结果提出了一个问题，即真核生物基因组的同调子组织在进化上起源于多远。
本研究涉及已获得完整基因组序列或至少支架的无脊椎动物的组成模式。我们发现：（i）同调子的镶嵌物是我们研究的所有基因组的长程组织；（ii）无脊椎动物基因组的同调子家族在 GC 水平上与脊椎动物的相应家族相匹配；（iii）同调子家族的相对数量对于不同的基因组差异显著，除了那些来自亲缘关系密切的物种，如果蝇。
这项工作不仅表明，同调子组织存在于包括线虫、原生动物中的节肢动物、后生动物中的棘皮动物和脊索动物在内的所有后生动物基因组中，而且无脊椎动物的同调子家族与脊椎动物的相应家族在 GC 水平上共享。
