\'The temporary knockdown of PfAP2-O leads to a complete loss of var 21 transcriptional memory and a decrease in cytoadherence. AP2-O-knocked down parasites exhibited 22 also significant reductions in transmission through Anopheles mosquitoes.\'

Normal gametocyte production and gamete formation. Evidence for normal fertilisation. Formation of retort shaped, immature ookinetes but no mature ookinete production.

The mutant parasites formed morphologically normal female and male gametocytes and exhibited normal exflagellation rates. However, they lacked the ability to infect mosquitoes as no oocysts or sporozoites were found in the mosquito. In culture, mutant parasites formed zygotes at normal conversion rates and differentiated into retort forms by 9 h after fertilization, as in wild type parasites. Subtle morphological differences between wild type and mutant parasites became visible 12 h after fertilization with a swelling protrusion in the retort forms. Mature ookinetes showed an aberrant morphology with an pear-shaped form, different from the banana (sword)-like form of wild type ookinetes.

Normal numbers of gametocytes are produced. Only ookinetes with aberrant morphology are produced.

No mature ookinete production. No oocyst production.

No oocyst and sporozoite production

\'The temporary knockdown of PfAP2-O leads to a complete loss of var 21 transcriptional memory and a decrease in cytoadherence. AP2-O-knocked down parasites exhibited 22 also significant reductions in transmission through Anopheles mosquitoes.\'

No oocyst and sporozoite production