Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, USA.
PLoS One. 2010 Aug 26;5(8):e12354. doi: 10.1371/journal.pone.0012354.
Apicomplexan parasites replicate by varied and unusual processes where the typically eukaryotic expansion of cellular components and chromosome cycle are coordinated with the biosynthesis of parasite-specific structures essential for transmission.
METHODOLOGY/PRINCIPAL FINDINGS: Here we describe the global cell cycle transcriptome of the tachyzoite stage of Toxoplasma gondii. In dividing tachyzoites, more than a third of the mRNAs exhibit significant cyclical profiles whose timing correlates with biosynthetic events that unfold during daughter parasite formation. These 2,833 mRNAs have a bimodal organization with peak expression occurring in one of two transcriptional waves that are bounded by the transition into S phase and cell cycle exit following cytokinesis. The G1-subtranscriptome is enriched for genes required for basal biosynthetic and metabolic functions, similar to most eukaryotes, while the S/M-subtranscriptome is characterized by the uniquely apicomplexan requirements of parasite maturation, development of specialized organelles, and egress of infectious daughter cells. Two dozen AP2 transcription factors form a series through the tachyzoite cycle with successive sharp peaks of protein expression in the same timeframes as their mRNA patterns, indicating that the mechanisms responsible for the timing of protein delivery might be mediated by AP2 domains with different promoter recognition specificities.
CONCLUSION/SIGNIFICANCE: Underlying each of the major events in apicomplexan cell cycles, and many more subordinate actions, are dynamic changes in parasite gene expression. The mechanisms responsible for cyclical gene expression timing are likely crucial to the efficiency of parasite replication and may provide new avenues for interfering with parasite growth.
顶复门寄生虫通过各种不同寻常的过程进行复制，其中细胞成分的典型真核扩展和染色体周期与寄生虫特异性结构的生物合成相协调，这些结构对于传播至关重要。
方法/主要发现：在这里，我们描述了刚地弓形虫速殖子阶段的全细胞周期转录组。在分裂的速殖子中，超过三分之一的 mRNA 表现出显著的周期性特征，其时间与在子虫形成过程中展开的生物合成事件相关。这 2833 个 mRNA 具有双峰组织，峰值表达发生在两个转录波之一中，这两个波由进入 S 期和细胞分裂后细胞周期退出的过渡所限制。G1-亚转录组富含基本生物合成和代谢功能所需的基因，与大多数真核生物相似，而 S/M-亚转录组的特征是寄生虫成熟、专门细胞器的发育和感染性子细胞逸出等独特的顶复门要求。二十几个 AP2 转录因子在速殖子周期中形成一系列，其蛋白表达的连续急剧峰值与它们的 mRNA 模式在同一时间范围内，表明负责蛋白传递时间的机制可能由具有不同启动子识别特异性的 AP2 结构域介导。
结论/意义：在顶复门细胞周期中的每一个主要事件和许多更次要的动作的背后，都是寄生虫基因表达的动态变化。周期性基因表达时间的机制可能对寄生虫复制的效率至关重要，并可能为干扰寄生虫生长提供新的途径。
