Pleiotropic Roles for the Plasmodium berghei RNA Binding Protein UIS12 in Transmission and Oocyst Maturation.

Katja Müller,Hans-Joachim Mollenkopf,Kai Matuschewski,Olivier Silvie

doi:10.3389/fcimb.2021.624945

Abstract

Colonization of the mosquito host by Plasmodium parasites is achieved by sexually differentiated gametocytes. Gametocytogenesis, gamete formation and fertilization are tightly regulated processes, and translational repression is a major regulatory mechanism for stage conversion. Here, we present a characterization of a Plasmodium berghei RNA binding protein, UIS12, that contains two conserved eukaryotic RNA recognition motifs (RRM). Targeted gene deletion resulted in viable parasites that replicate normally during blood infection, but form fewer gametocytes. Upon transmission to Anopheles stephensi mosquitoes, both numbers and size of midgut-associated oocysts were reduced and their development stopped at an early time point. As a consequence, no salivary gland sporozoites were formed indicative of a complete life cycle arrest in the mosquito vector. Comparative transcript profiling in mutant and wild-type infected red blood cells revealed a decrease in transcript abundance of mRNAs coding for signature gamete-, ookinete-, and oocyst-specific proteins in uis12(-) parasites. Together, our findings indicate multiple roles for UIS12 in regulation of gene expression after blood infection in good agreement with the pleiotropic defects that terminate successful sporogony and onward transmission to a new vertebrate host.

Highlights

During the complex life cycle of Plasmodium, malarial parasites switch between different host cells, extra- and intracellular life cycle forms, and an invertebrate and a vertebrate host
We initiated our analysis by an NCBI conserved domain database (CDD) search (Marchler-Bauer et al, 2015), which revealed two ~70 amino acid long RNA-recognition motifs (RRM), belonging to the class of RNA-binding domains (RBD) (Dreyfuss et al, 1988), in the P. berghei up-regulated in infectious sporozoites gene 12 (UIS12) protein sequence
The defects of uis12(-) parasites during host switching cannot be compensated for in subsequent steps in the Plasmodium life cycle, and uis12(-) infection leads to fewer oocysts, which fail to undergo oocyst maturation

Summary

Introduction

During the complex life cycle of Plasmodium, malarial parasites switch between different host cells, extra- and intracellular life cycle forms, and an invertebrate and a vertebrate host. Many genes needed for gametocytogenesis and early events of mosquito colonization are transcribed by the interplay of the Plasmodium transcription factors AP2-G and AP2-I, while asexual gene expression is repressed by AP2-G2 and AP2-FG controls female-specific gene regulation (Sinha et al, 2014; Yuda et al, 2015; Josling et al, 2020; Yuda et al, 2020). This transcriptional switch leads to the expression of mRNAs which are required for the multiple steps from gametocytogenesis to zygote formation until the motile ookinete stage is reached and the checkpoint in transcription control is initiated by the AP2-O 1-4 family (Kaneko et al, 2015; Modrzynska et al, 2017). A tight fine-tuning is essential to synthesize tailored proteins at the right time

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Conclusion