Plasmodium male gametocyte development and transmission are critically regulated by general and transmission-specific members of the CAF1/CCR4/NOT complex

With relatively few known specific transcription factors to control the abundance of specific mRNAs, Plasmodium parasites also regulate the stability and turnover of transcripts to provide more comprehensive gene regulation. Plasmodium transmission stages impose translational repression on specific transcripts in part to accomplish this. However, few proteins are known to participate in this process, and those that are characterized primarily affect female gametocytes. We have identified and characterized PyCCR4-1, a putative deadenylase, which plays a role in the development and activation of male gametocytes, regulates the abundance of specific mRNAs in gametocytes, and ultimately increases the efficiency of host-to-vector transmission. We find that when pyccr4-1 is deleted or its protein made catalytically inactive, there is a loss in the initial coordination of male gametocyte maturation and a reduction of parasite infectivity of the mosquito. Expression of only the N-terminal CAF1 domain of the essential CAF1 deadenylase, which prevents PyCCR4-1 association with the complex, leads to a similar phenotype. Comparative RNA-seq revealed that PyCCR4-1 affects transcripts important for transmission-related functions that are associated with male or female gametocytes, some of which directly associate with the immunoprecipitated complex. Finally, circular RT-PCR of one of the bound, dysregulated transcripts showed that PyCCR4-1 does not have gross changes in UTR or poly(A) tail length. We conclude that general and transmission-specialized members of the CAF1/CCR4/NOT complex play critical and intertwined roles in gametocyte maturation and transmission.