Plasmodium falciparum is the main causative agent of human malaria. During the intraerythrocytic development cycle, the P. falciparum morphology changes dramatically from circulating young rings to sequestered mature trophozoites and schizonts. Sequestered forms contribute to the pathophysiology of severe malaria as the infected erythrocytes obstruct the microvascular flow in deep organs and induce local inflammation. However, the sequestration mechanism limits the access to the corresponding parasitic form in the clinical samples from patients infected with P. falciparum. To complement this deficiency, we aimed to evaluate the relevance of mRNA study as a proxy of protein expression in sequestered parasites. To do so, we conducted a proteotranscriptomic analysis using five independent P. falciparum laboratory strain samples. RNA sequencing was performed, and the mRNA expression level was assessed on circulating ring-stage parasites. The level of protein expression were measured by LC−MS/MS on the corresponding sequestered mature forms after 18–24 h of maturation. Overall, our results showed a strong transcriptome/transcriptome and a very strong proteome/proteome correlation between samples. Moreover, positive correlations of mRNA and protein expression levels were found between ring-stage transcriptomes and mature form proteomes. However, twice more transcripts were identified at the ring stage than proteins at the mature trophozoite stage. A high level of transcript expression did not guarantee the detection of the corresponding protein. Finally, we pointed out discrepancies at the individual gene level. Taken together, our results show that transcript and protein expressions are overall correlated. However, mRNA abundance is not a perfect proxy of protein expression at the individual level. Importantly, our study shows limitations of the “blind” use of RNA-seq and the importance of multiomics approaches for P. falciparum blood stage study in clinical samples.

中文翻译：

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恶性疟原虫感染血液中转录本和蛋白质相对丰度的综合分析

恶性疟原虫是人类疟疾的主要病原。在红细胞内发育周期中，恶性疟原虫的形态从循环的幼环到螯合的成熟滋养体和裂殖体都发生了巨大变化。螯合形式有助于严重疟疾的病理生理，因为被感染的红细胞阻碍深部器官中的微血管流动并引起局部炎症。然而，螯合机制限制了恶性疟原虫感染患者获得临床样品中相应寄生虫形式的机会。为了弥补这一不足，我们旨在评估mRNA研究作为螯合寄生虫中蛋白质表达的代理的相关性。为此，我们使用五个独立的恶性疟原虫进行了蛋白转录组学分析实验室菌株样品。进行RNA测序，并在循环的环形阶段寄生虫上评估mRNA表达水平。在18-24小时成熟后，通过LC-MS / MS测定相应螯合的成熟形式上的蛋白质表达水平。总体而言，我们的结果表明样本之间的转录组/转录组很强，蛋白质组/蛋白质组的相关性很强。此外，发现环形阶段的转录组和成熟形式的蛋白质组之间的mRNA和蛋白质表达水平的正相关。然而，在环阶段鉴定出的转录物比在成熟滋养体阶段的蛋白质多两倍。高水平的转录表达不能保证检测到相应的蛋白质。最后，我们指出了个体基因水平上的差异。在一起 我们的结果表明，转录本和蛋白质表达总体上相关。然而，在个体水平上，mRNA丰度并不是蛋白质表达的完美替代。重要的是，我们的研究显示了RNA seq的“盲目”使用的局限性以及使用多组学方法进行RNA测序的重要性。临床样本中恶性疟原虫血液阶段的研究。