Genome Biol. 2013 Jul 26;14(7):R77. doi: 10.1186/gb-2013-14-7-r77.
Several eukaryotic parasites form cysts that transmit infection. The process is found in diverse organisms such as Toxoplasma, Giardia, and nematodes. In Entamoeba histolytica this process cannot be induced in vitro, making it difficult to study. In Entamoeba invadens, stage conversion can be induced, but its utility as a model system to study developmental biology has been limited by a lack of genomic resources. We carried out genome and transcriptome sequencing of E. invadens to identify molecular processes involved in stage conversion.
We report the sequencing and assembly of the E. invadens genome and use whole transcriptome sequencing to characterize changes in gene expression during encystation and excystation. The E. invadens genome is larger than that of E. histolytica, apparently largely due to expansion of intergenic regions; overall gene number and the machinery for gene regulation are conserved between the species. Over half the genes are regulated during the switch between morphological forms and a key signaling molecule, phospholipase D, appears to regulate encystation. We provide evidence for the occurrence of meiosis during encystation, suggesting that stage conversion may play a key role in recombination between strains.
Our analysis demonstrates that a number of core processes are common to encystation between distantly related parasites, including meiosis, lipid signaling and RNA modification. These data provide a foundation for understanding the developmental cascade in the important human pathogen E. histolytica and highlight conserved processes more widely relevant in enteric pathogens.
几种真核寄生虫形成包囊以传播感染。该过程存在于多种生物体中，如弓形虫、贾第鞭毛虫和线虫。在溶组织内阿米巴中，无法在体外诱导该过程，因此难以进行研究。在侵袭性内阿米巴中，可以诱导阶段转换，但由于缺乏基因组资源，其作为研究发育生物学的模型系统的实用性受到限制。我们对侵袭性内阿米巴进行了基因组和转录组测序，以鉴定参与阶段转换的分子过程。
我们报告了侵袭性内阿米巴基因组的测序和组装，并利用全转录组测序来描述囊化和出囊过程中基因表达的变化。侵袭性内阿米巴的基因组大于溶组织内阿米巴，显然主要是由于基因间区的扩张；物种间的基因总数和基因调控机制是保守的。超过一半的基因在形态转换之间受到调控，一种关键的信号分子磷脂酶 D 似乎调节囊化。我们提供了在囊化过程中发生减数分裂的证据，表明阶段转换可能在菌株间重组中发挥关键作用。
我们的分析表明，一些核心过程在亲缘关系较远的寄生虫之间的囊化中是共同的，包括减数分裂、脂质信号和 RNA 修饰。这些数据为理解重要的人类病原体溶组织内阿米巴的发育级联提供了基础，并突出了在肠道病原体中更广泛相关的保守过程。
