Figure 9: PbNPT1 is essential for microgametogenesis and mediates the uptake of cationic amino acids into P. berghei parasites.

(a) Quantification of microgamete formation in WT and ΔPbnpt1 parasites by measuring [³H]hypoxanthine incorporation following induction of microgametogenesis by temperature shift and the addition of xanthurenic acid⁵⁴. Data were averaged from three biological replicates, and are shown±s.e.m. (*P<0.05; Student’s t test). (b) Uptake of [¹⁴C]Arg, [¹⁴C]Lys and [¹⁴C]2-DOG by asexual-stage WT (black) or ΔPbnpt1 (grey) parasites, isolated from their host erythrocytes by saponin permeabilisation of the host erythrocyte and parasitophorous vacuole membranes. The isolated parasites were suspended in PBS containing either 0.1?μCi?ml⁻¹ (289?nM) [¹⁴C]Arg, 0.1?μCi?ml⁻¹ (307?nM) [¹⁴C]Lys, or 0.1?μCi?ml⁻¹ (1.8?μM) [¹⁴C]2-DOG. Incorporation was measured after 4?min, a time point that is approximately within the linear uptake phase of arginine in P. falciparum³¹. Results are expressed as mean±s.e.m., n=3 (*P<0.05; n.s.=not significant; ANOVA).