Identification of a transcription factor in the mosquito-invasive stage of malaria parasites.

Gene expression in Plasmodium parasites undergoes significant changes in each developmental stage, but the transcription factors (TFs) regulating these changes have not been identified. We report here a Plasmodium TF (AP2-O) that activates gene expression in ookinetes, the mosquito-invasive form, and has a DNA-binding domain structurally related to that of a plant TF, Apetala2 (AP2). AP2-O mRNA is pre-synthesized by intraerythrocytic female gametocytes and translated later during ookinete development in the mosquito. The Plasmodium TF activates a set of genes, including all genes reported to be required for midgut invasion, by binding to specific six-base sequences on the proximal promoter. These results indicate that AP2 family TFs have important roles in stage-specific gene regulation in Plasmodium parasites.