Figure 3.

Transgenic expression of the PbSUB1 prodomain reduces endogenous PbSUB1 protease activity and inhibits exflagellation. (a) IFA of the transgenic line SUB1/prod with an anti‐HA antibody. Anti‐PbSUB1 was used as an OB marker. Nuclei are stained with DAPI. Scale bar 5 μm. (b) IFA of Plasmodium berghei blood stages with anti‐SERA3. Anti‐Sep1 antibody was used as a PVM marker; anti‐SET antibody was used as a gender marker; nuclei are stained with DAPI. Scale bar 5 μm. (c) Western blot analysis with anti‐PbSERA3 of extracts from 5 × 10⁶ wt gametocytes (gams) and 5 × 10⁶ SUB1/prod gametocytes, wt exflagellation supernatants (exfl. sup.) from 5 × 10⁶ gametocytes, and SUB1/prod exflagellation supernatants from 5 × 10⁶ gametocytes. Anti‐SUB1 was used as a loading control. Asterisks highlight the seven main processing products: PbSERA3‐130, PbSERA3‐110, PbSERA3‐100, PbSERA3‐72, PbSERA3‐55, PbSERA3‐65, and PbSERA3‐48. Red asterisks highlight the full‐length protein and the terminal processing product PbSERA3‐48. This experiment was conducted in two biological replicates, both showing the same processing pattern in gametocytes and exflagellation supernatants. (d) Exflagellation rates of the SUB1/prod line in two independent experiments, each performed in triplicate, at 15 min postinduction, expressed as a percentage of exflagellation rates in the wt line (Student's t test: p_exp1 < 0.005 and p_exp2 < 1.02 × 10⁻⁵; error bars represent +/− standard deviation of the mean value)