Abstract
The egress and fertilization of Plasmodium gametes and development of a motile ookinete are the first crucial steps that mediate the successful transmission of the malaria parasites from humans to the Anopheles vector. However, limited information exists about the cell biology and regulation of this process. Technical impediments in the establishment of in vitro conditions for ookinete maturation in Plasmodium falciparum and other human malaria parasites further constrain a detailed characterization of ookinete maturation. Here, using fluorescence microscopy and immunolabeling, we compared P. falciparum ookinete maturation in Anopheles coluzzii mosquitoes in vivo and in cell culture in vitro. Our results identified two critical steps in ookinete maturation that are regulated by distinct mosquito factors, thereby highlighting the role of the mosquito environment in the transmission efficiency of malaria parasites.
Highlights
Malaria is a mosquito-borne disease, mainly caused by the protozoan parasite Plasmodium falciparum, which kills 429,000 people annually (World Health Organization [WHO], 2018)
To characterize the major stages of zygote development, we performed a time course fluorescence live microscopy analysis of the blood bolus content of A. coluzzii mosquitoes infected with gametocyte cultures of P. falciparum
As these forms were only observed after appearance of mature ookinetes at the late time point of ookinete development in vivo, we speculate that ghosts represent ookinetes undergoing degradation probably due to the harsh environment of the mosquito midgut
Summary
Malaria is a mosquito-borne disease, mainly caused by the protozoan parasite Plasmodium falciparum, which kills 429,000 people annually (World Health Organization [WHO], 2018). Plasmodium transmission is initiated within minutes after blood ingestion by the Anopheles mosquito. The gametocytes transform into mature extracellular female and male gametes. The product of fertilization, the zygote, takes one day to transform into a motile ookinete, which traverses the midgut epithelium to establish oocyst infection on the basal side. During the first 24 h after blood meal, the parasites undergo a series of radical tightly regulated morphological changes: gamete roundup, egress and exflagellation, formation of a zygote, emergence of an elongated protuberance and transformation of a round zygote into a crescent-shaped motile ookinete. The early stages of gametocyte-to-gamete transformation are triggered by the mosquito-derived metabolite xanthurenic acid, which together with the temperature drop signals for gamete egress and exflagellation (Billker et al, 1998). Field studies suggested that pre-fertilization events do not reliably predict the outcome of mosquito infection, as the numbers of the blood-circulating gametocytes do not always correlate with the donor infectiousness
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
