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Global Release of Translational Repression Across Plasmodium’s Host-to-Vector Transmission Event

ABSTRACT: Malaria parasites must be able to respond quickly to their environment, including during their transmission between mammalian hosts and mosquito vectors. Therefore, before transmission, female gametocytes proactively produce and translationally repress mRNAs that encode essential proteins that the zygote requires to establish a new infection. This essential regulatory control requires the orthologues of DDX6 (DOZI) and LSM14 (CITH), which along with ALBA proteins, form a translationally repressive complex in female gametocytes that associates with many of the affected mRNAs. However, while the release of translational repression of individual mRNAs has been documented, the details of the global release of translational repression have not. Moreover, the changes in spatial arrangement and composition of the DOZI/CITH/ALBA complex that contribute to translational control are also not known. Therefore, we have conducted the first comparative transcriptomics and proteomics of Plasmodium parasites across the host-to-vector transmission event to document the global release of translational repression. Using female gametocytes and zygotes of P. yoelii, we find that over 200 transcripts are released for translation soon after fertilization, including those with essential functions for the zygote. However, we also observed that some transcripts remain repressed beyond this point. In addition, we have used TurboID-based proximity proteomics to interrogate the spatial and compositional changes in the DOZI/CITH/ALBA complex across this transmission event. Consistent with recent models of translational control, proteins that associate with either the 5’ or 3’ end of mRNAs are in close proximity to one another during translational repression in female gametocytes and then dissociate upon release of repression in zygotes. These protein interactions in female gametocytes were further validated through structured illumination microscopy and ultrastructure expansion microscopy. Together, these data provide a model for the essential translational control mechanisms used by malaria parasites to promote their efficient transmission.

ORGANISM(S): Plasmodium yoelii

PROVIDER: GSE231838 | GEO | 2023/05/10

REPOSITORIES: GEO

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Project description:The transmission of the malaria parasite between mosquitoes and mammals requires translational repression to ensure that only the proper proteins are expressed at the right time, while still allowing the parasite to prepare the mRNAs it will need for the next developmental stage. With relatively few known specific transcription factors (ApiAP2 family) that may specifically initiate gene transcription, Plasmodium parasites also regulate the stability and turnover of transcripts to provide more comprehensive gene regulation. The CAF1/CCR4/NOT complex has been shown in model organisms to be important for not only mRNA degradation, but also translational control through its deadenylases CAF1 and CCR4. However, few proteins that impose translational repression in Plasmodium sexual stages are known, and those that are characterized primarily affect female gametocytes. Therefore, we have characterized two deadenylases and have uncovered their roles in transmission. We have identified and characterized CCR4-1, which we show plays a role in activating male gametocytes, stabilizing transcripts in gametocytes, and regulating host-to-vector transmission. We find that when ccr4-1 is genetically deleted, there is a loss in the coordination of male gametocyte activation and a reduction in the ability of the parasite to productively infect the mosquito, which is independent of its effect upon male activation. Comparative RNA-seq shows that the deletion of ccr4-1 affects many transcripts that are translationally repressed in females, are related to male gamete function, and/or are important for early mosquito stage development. In contrast, we found that genetic deletion of the major deadenylase Caf1 is lethal. However, we observed that expression of only the N-terminal Caf1 domain is permissive, yet prevents proper complex assembly and phenocopies the ccr4-1 deletion. We therefore conclude that the general and transmission-specialized deadenylases of the CAF1/CCR4/NOT complex play critical and intertwined roles in parasite growth and transmission.

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Global Release of Translational Repression Across Plasmodium’s Host-to-Vector Transmission Event

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