Plasmodium DEH is ER-localized and crucial for oocyst mitotic division during malaria transmission

Cells use fatty acids (FAs) for membrane biosynthesis, energy storage and the generation of signaling molecules. 3-hydroxyacyl-CoA dehydratase – DEH – is a key component of very long chain FA (VLCFA) synthesis. Here, we further characterized in-depth the location and function of DEH, applying in silico analysis, live cell imaging, reverse genetics and ultrastructure analysis using the mouse malaria model Plasmodium berghei . DEH is evolutionarily conserved across eukaryotes, with a single DEH in Plasmodium spp. and up to three orthologs in the other eukaryotes studied. DEH-GFP live-cell imaging showed strong GFP fluorescence throughout the life-cycle, with areas of localized expression in the cytoplasm and a circular ring pattern around the nucleus that colocalized with ER markers. Δ deh mutants showed a small but significant reduction in oocyst size compared to WT controls from day 10 post-infection onwards and endomitotic cell division and sporogony were completely ablated, blocking parasite transmission from mosquito to vertebrate host. Ultrastructure analysis confirmed degeneration of Δ deh oocysts, and a complete lack of sporozoite budding. Overall, DEH is evolutionarily conserved, localizes to the ER and plays a crucial role in sporogony.