后生超级进化枝Lophotrochozoa包括软体动物,环节动物,和其他几只动物门。可以合理地假设这种生物多样性可以被追踪,在某种程度上,发育重要基因的变化,比如同源异型盒基因。虽然大多数比较研究都集中在古代同源异型盒基因家族,还有最近在进化中出现的“新的”同源异型盒基因,可能是重复,然后是激进的分歧和功能变化。我们对太平洋牡蛎基因组序列中的136个同源异型盒基因进行了分类,Crassostreagigas.基因组显示异型盒基因聚类程度异常低,随着NK的破坏,Hox,和ParaHox基因簇。在牡蛎基因中,31个不属于古代后生动物或双边同源盒基因家族;我们推断它们起源于lophrochozoan进化枝。我们比较了八个lophrochozoan基因组,以追踪该进化枝的同源盒基因进化模式,允许我们在ANTP中定义19个新的特定于lophrochozoan的进化枝,PRD,TALE,ZF,六,和CUT类。利用转录组数据,我们比较了牡蛎发育中每个同源异型盒基因的时间表达,并发现异色虫特异性同源异型盒基因在早期发育(卵到胃)或晚期发育(在营养体幼虫阶段之后)具有高峰表达,但很少介于两者之间。这一发现与鸡蛋计时器一致,沙漏或发育进化的生理阶段模型,其中有一个保守的发展中心阶段,但在进化上更不稳定的早期和晚期。
The metazoan superclade Lophotrochozoa includes mollusks, annelids, and several other animal phyla. It is reasonable to assume that this organismal diversity may be traced, in part, to changes in developmentally important genes, such as the homeobox genes. Although most comparative studies have focussed on ancient homeobox gene families conserved across bilaterians, there are also \"novel\" homeobox genes that have arisen more recently in evolution, presumably by duplication followed by radical divergence and functional change. We classify 136 homeobox genes in the genome sequence of the Pacific oyster, Crassostrea gigas. The genome shows an unusually low degree of homeobox gene clustering, with disruption of the NK, Hox, and ParaHox gene clusters. Among the oyster genes, 31 do not fall into ancient metazoan or bilaterian homeobox gene families; we deduce that they originated in the lophotrochozoan clade. We compared eight lophotrochozoan genomes to trace the pattern of homeobox gene evolution across this clade, allowing us to define 19 new lophotrochozoan-specific clades within the ANTP, PRD, TALE, ZF, SIX, and CUT classes. Using transcriptome data, we compared temporal expression of each homeobox gene in oyster development, and discovered that the lophotrochozoan-specific homeobox genes have peak expression either in early development (egg to gastrula) or in late development (after the trochophore larval stage), but rarely in between. This finding is consistent with the egg-timer, hourglass or phylotypic stage model of developmental evolution, in which there is a conserved central phase of development, but more evolutionarily labile early and late phases.