Abstract：
Asexual replication in the apicomplexan Sarcocystis neurona involves two main developmental stages: the motile extracellular merozoite and the sessile intracellular schizont. Merozoites invade host cells and transform into schizonts that undergo replication via endopolygeny to form multiple (64) daughter merozoites that are invasive to new host cells. Given that the capabilities of the merozoite vary significantly from the schizont, the patterns of transcript levels throughout the asexual lifecycle were determined and compared in this study. RNA-Seq data were generated from extracellular merozoites and four intracellular schizont development time points. Of the 6,938 genes annotated in the S. neurona genome, 6,784 were identified in the transcriptome. Of these, 4,111 genes exhibited significant differential expression between the merozoite and at least one schizont development time point. Transcript levels were significantly higher for 2,338 genes in the merozoite and 1,773 genes in the schizont stages. Included in this list were genes encoding the secretory pathogenesis determinants (SPDs), which encompass the surface antigen and SAG-related sequence (SAG/SRS) and the secretory organelle proteins of the invasive zoite stage (micronemes, rhoptries, and dense granules). As anticipated, many of the S. neurona SPD gene transcripts were abundant in merozoites. However, several SPD transcripts were elevated in intracellular schizonts, suggesting roles unrelated to host cell invasion and the initial establishment of the intracellular niche. The hypothetical genes that are potentially unique to the genus Sarcocystis are of particular interest. Their conserved expression patterns are instructive for future investigations into the possible functions of these putative Sarcocystis-unique genes.
OBJECTIVE: The genus Sarcocystis is an expansive clade within the Apicomplexa, with the species S. neurona being an important cause of neurological disease in horses. Research to decipher the biology of S. neurona and its host-pathogen interactions can be enhanced by gene expression data. This study has identified conserved apicomplexan orthologs in S. neurona, putative Sarcocystis-unique genes, and gene transcripts abundant in the merozoite and schizont stages. Importantly, we have identified distinct clusters of genes with transcript levels peaking during different intracellular schizont development time points, reflecting active gene expression changes across endopolygeny. Each cluster also has subsets of transcripts with unknown functions, and investigation of these seemingly Sarcocystis-unique transcripts will provide insights into the interesting biology of this parasite genus.
OBJECTIVE: The genus Sarcocystis is an expansive clade within the Apicomplexa, with the species S. neurona being an important cause of neurological disease in horses. Research to decipher the biology of S. neurona and its host-pathogen interactions can be enhanced by gene expression data. This study has identified conserved apicomplexan orthologs in S. neurona, putative Sarcocystis-unique genes, and gene transcripts abundant in the merozoite and schizont stages. Importantly, we have identified distinct clusters of genes with transcript levels peaking during different intracellular schizont development time points, reflecting active gene expression changes across endopolygeny. Each cluster also has subsets of transcripts with unknown functions, and investigation of these seemingly Sarcocystis-unique transcripts will provide insights into the interesting biology of this parasite genus.
摘要：
尖丛中的无性复制Sarcocystis神经元涉及两个主要的发育阶段：能动的细胞外裂殖子和无柄的细胞内裂殖体。孢子侵入宿主细胞并转化为裂殖体，这些裂殖体通过内聚发生进行复制，形成对新宿主细胞具有侵袭性的多个（64个）子裂殖体。鉴于裂殖子的能力与裂殖子的能力差异很大，本研究确定并比较了整个无性生命周期中的转录水平模式.从细胞外裂殖子和四个细胞内裂殖体发育时间点产生RNA-Seq数据。在S.Neuroona基因组中注释的6,938个基因中，在转录组中鉴定了6,784。其中,4,111个基因在裂殖子和至少一个裂殖体发育时间点之间表现出明显的差异表达。裂殖子的2,338个基因和裂殖体阶段的1,773个基因的转录水平明显更高。该列表中包括编码分泌性发病机理决定子（SPD）的基因，其中包含表面抗原和SAG相关序列（SAG/SRS）和侵袭性动物阶段的分泌细胞器蛋白（微粒，rhoptries,和致密的颗粒）。如预期,许多神经链球菌SPD基因转录本在裂殖子中丰富。然而,细胞内裂殖体的几种SPD转录物升高，提示与宿主细胞侵袭和细胞内生态位的初步建立无关的作用。特别令人感兴趣的是对于肉囊虫属潜在独特的假设基因。它们保守的表达模式对于将来研究这些推定的Sarcocystis独特基因的可能功能具有指导意义。
目的：结节虫属是顶波内的一个膨胀进化枝，神经链球菌是马神经系统疾病的重要原因。基因表达数据可以增强破译神经链球菌生物学及其宿主-病原体相互作用的研究。这项研究已经确定了S.neurona中保守的尖丛直系同源物，推测的肉囊虫独特基因，和裂殖子阶段丰富的基因转录本。重要的是,我们已经确定了不同的基因簇，其转录水平在不同的细胞内裂殖体发育时间点达到峰值，反映了整个内聚基因的活性基因表达变化。每个簇还具有功能未知的转录本子集，对这些看似Sarcocystis独特的转录本的研究将为该寄生虫属的有趣生物学提供见解。
目的：结节虫属是顶波内的一个膨胀进化枝，神经链球菌是马神经系统疾病的重要原因。基因表达数据可以增强破译神经链球菌生物学及其宿主-病原体相互作用的研究。这项研究已经确定了S.neurona中保守的尖丛直系同源物，推测的肉囊虫独特基因，和裂殖子阶段丰富的基因转录本。重要的是,我们已经确定了不同的基因簇，其转录水平在不同的细胞内裂殖体发育时间点达到峰值，反映了整个内聚基因的活性基因表达变化。每个簇还具有功能未知的转录本子集，对这些看似Sarcocystis独特的转录本的研究将为该寄生虫属的有趣生物学提供见解。
