Fig. 7: Environmental heme from the host cell plays a key role in the development of Plasmodium exo-erythrocytic schizonts.

a Expression of P. berghei heme biosynthesis genes throughout the parasite’s life cycle. Most parasite genes are expressed at low levels during the liver stage (EEF), except for FECH. EEF: exo-erythrocytic form; DC: detached mammalian cell containing merosomes. b Western blot of whole cell lysates from HAP1 wild type, ΔHMBS clone (cl.) A, and a pool of ΔHMBS cl. A::HMBS complemented cells. HMBS and tubulin (as control) were detected with specific antibodies as described in Methods. Scale bar = 60 µm. This experiment has been repeated multiple times (>3) with similar results. c Phase contrast images of HAP1 wild type and HAP1 ΔHMBS cl. A after 48 h incubation in normal 10% FCS-IMD media, heme-depleted 10% FCS-IMDM, and the latter with hemin supplementation. d P. berghei exo-erythrocytic schizont size at 48 h pi in HAP1 WT and six HAP1 ΔHMBS clones A - F. Cells were infected with mCherry-expressing P. berghei sporozoites and size was determined using automated imaging. The graph shows sizes of individual parasites (n = 27–99) with median and interquartile range. e Parasite size at 48 hpi in HAP1 WT, ΔHMBS cl. A, and ΔHMBS cl. A::HMBS complementation. Infection and size measurements were done as described in (d). The graph shows sizes of individual parasites (n = 92) and includes means with SD and p values of one-way ANOVA analysis with Dunnett’s multiple comparison test.